Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Clinical Psychology Review 31 (2011) 1022–1031 Contents lists available at ScienceDirect Clinical Psychology Review The efficacy of hypnosis as an intervention for labor and delivery pain: A comprehensive methodological review Alison S. Landolt, Leonard S. Milling ⁎ University of Hartford, USA a r t i c l e i n f o Article history: Received 9 February 2011 Received in revised form 26 May 2011 Accepted 1 June 2011 Available online 23 June 2011 Keywords: Labor and delivery pain Hypnosis Treatment outcomes Methodology a b s t r a c t This paper presents a comprehensive methodological review of research on the efficacy of hypnosis for reducing labor and delivery pain. To be included, studies were required to use a between-subjects or mixed model design in which hypnosis was compared with a control condition or alternative intervention in reducing labor pain. An exhaustive search of the PsycINFO and PubMed databases produced 13 studies satisfying these criteria. Hetero-hypnosis and self-hypnosis were consistently shown to be more effective than standard medical care, supportive counseling, and childbirth education classes in reducing pain. Other benefits included better infant Apgar scores and shorter Stage 1 labor. Common methodological limitations of the literature include a failure to use random assignment, to specify the demographic characteristics of samples, and to use a treatment manual. © 2011 Elsevier Ltd. All rights reserved. Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 1.1. Biology of labor and delivery . . . . . . . . . . . . . 1.2. Common pharmacologic methods of pain control . . . 1.3. Hypnosis as an intervention for labor and delivery pain 2. Method of review . . . . . . . . . . . . . . . . . . . . . 3. Summary of controlled studies . . . . . . . . . . . . . . . 3.1. Hypnosis versus standard medical care . . . . . . . . 3.2. Hypnosis versus supportive counseling . . . . . . . . 3.3. Hypnosis versus Lamaze . . . . . . . . . . . . . . . 3.4. Hypnosis versus childbirth education classes . . . . . 4. Methodological considerations . . . . . . . . . . . . . . . 4.1. Random assignment . . . . . . . . . . . . . . . . . 4.2. Specification of sample . . . . . . . . . . . . . . . . 4.3. Treatment manual . . . . . . . . . . . . . . . . . . 4.4. Hypnotic context . . . . . . . . . . . . . . . . . . 4.5. Active use of hypnosis . . . . . . . . . . . . . . . . 4.6. Hypnotic suggestibility . . . . . . . . . . . . . . . . 4.7. Other methodological considerations . . . . . . . . . 5. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1022 1023 1023 1023 1024 1024 1024 1025 1026 1026 1027 1027 1028 1028 1028 1028 1029 1029 1029 1030 1030 1. Introduction ⁎ Corresponding author at: University of Hartford, Department of Psychology, 200 Bloomfield Avenue, West Hartford, CT 06117, USA. Tel.: + 1 860 768 4546; fax: + 1 860 768 5292. E-mail address: [email protected] (L.S. Milling). 0272-7358/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.cpr.2011.06.002 Pain during labor and delivery presents a distinct problem for expectant mothers. Many pregnant women greatly fear the pain of childbirth, and this fear, as well as anxiety, is associated with a greater experience of pain (Leeman, Fontaine, King, Klein, & Ratcliffe, 2003; A.S. Landolt, L.S. Milling / Clinical Psychology Review 31 (2011) 1022–1031 Simkin, 2000). Labor pain, which is primarily experienced during contractions in the first and second stages of labor, varies greatly among women (Niven & Murphy-Black, 2000). Despite this variability, labor pain is usually intense and is often described by women as the most extreme pain ever experienced (Niven & Murphy-Black, 2000). For example, during a two-week period in a major Swedish city, Waldenström, Bergman, and Vasell (1996) asked all women who gave birth during that time, except for those who did not speak Swedish and women who underwent elective cesarean sections, about their experiences of labor pain two days after delivery. Of the 278 women who participated in the study, 41% rated the discomfort of labor as the worst pain imaginable. Notably, these findings were obtained despite the widespread use of pharmacologic interventions to provide relief. In fact, only 9% of the participants refrained from using analgesia. 1.1. Biology of labor and delivery The process of childbirth consists of three stages of labor (Harms, 2004). The first stage of labor is characterized by uterine contractions, which force the baby against the cervix, and cervical dilation, which allows the baby to descend into the vagina. This stage is divided into three phases: early labor, active labor, and transition (Harms, 2004). During early labor, contractions last between thirty and sixty seconds and range from five to twenty minutes apart. The cervix dilates from zero to just over three centimeters, comprising the longest but least intense period of labor. Active labor is shorter than early labor, but is much more intense as contractions become more painful (Harms, 2004). It is during this phase that many women request pain medication, and epidurals, if used, are typically administered at this time. Transition, during which the cervix dilates from seven to the full ten centimeters, is the shortest, but most difficult phase. Contractions increase in strength and frequency, lasting from sixty to ninety seconds. Intravenous and intramuscular pain medication is usually contraindicated during this phase due to the proximity to birth. This is because intravenous and intramuscular pain medication could depress respiratory functioning in the infant (Harms, 2004), although epidurals may still be given if time permits. The second stage of labor, also known as the pushing stage, begins after full cervical dilation is attained and concludes once the infant's body has been fully birthed (Littleton & Engebretson, 2004; Pillitteri, 2009). This stage is characterized by intense, forceful contractions and, for some, burning pain in the perineum. The third stage of labor involves the delivery of the placenta, an organ inside the uterus that provides nourishment to the fetus through the umbilical cord (Harms, 2004). In order to facilitate delivery of the placenta, also called the afterbirth, mild contractions continue during this stage. 1.2. Common pharmacologic methods of pain control Both pharmacologic and non-pharmacologic methods are used for pain management during labor and delivery. Pharmacologic interventions administered during childbirth, however, present special concerns. For example, the effects on the infant must be considered and many drugs must be given within certain time frames in order to satisfy safety and efficacy concerns (Simpson & Creehan, 2008). In regional anesthesia, injection of local anesthesia is used to block specific nerve pathways, thus providing pain relief (Pillitteri, 2009). An advantage of regional anesthesia is that it allows the woman to be awake and fully aware of the birth experience. One form of regional anesthesia is the epidural, which is one of the most common pharmacologic methods of pain relief during childbirth. Although epidurals provide an effective means of pain control during labor and delivery, there is some evidence that women who receive epidural anesthesia experience significantly longer Stage 2 labor 1023 and an increased risk of hypotension, instrumental delivery, and motor blockade than women who do not utilize epidurals (see Anim-Somuah, Smyth, & Howell, 2005). Similarly, Thorp and Breedlove (1996) reported that epidural anesthesia was associated with longer labor and an increased risk of instrumental delivery. According to Littleton and Engebretson (2004), epidural anesthesia may interfere with a woman's ability to push forcefully. This may explain why the second stage of labor – the pushing stage – is longer when an epidural is used. Another pharmacologic intervention, low spinal anesthesia, also called saddle block, is easy to administer, works rapidly, and provides an effective form of pain relief (Creasy, Resnik, & Iams, 2004). However, it often interferes with the expectant mother's ability to push during labor — even more so than epidural anesthesia. Some narcotic analgesics such as Meperidine (Demerol) and Morphine Sulfate provide beneficial analgesic effects during labor; however, they may result in respiratory depression in the newborn (Pillitteri, 2009). Indeed, the neurobehavioral depression (e.g., poor sucking response, depressed respiration, decreased alertness and attention, poor muscle tone) in the newborn caused by Meperidine can last for several days (Simpson & Creehan, 2008). 1.3. Hypnosis as an intervention for labor and delivery pain Hypnosis is an intervention that has been shown to be effective for reducing a variety of forms of pain (reviewed in Patterson & Jensen, 2003). Hypnosis is defined as “a procedure during which a health professional or researcher suggests that a client, patient, or subject experience changes in sensations, perceptions, thoughts or behavior” (Kirsch, 1994, p. 143). Hypnosis typically involves two individuals—a hypnotist and a person who is being hypnotized (i.e., hetero-hypnosis). However, in self-hypnosis, a single individual assumes both roles and the patient or client delivers suggestions for changes in experience to herself or himself. Every hypnotic procedure consists of a hypnotic induction and suggestions (Hilgard, 1965). The induction establishes a hypnotic context and typically includes instructions for relaxation and wellbeing, accompanied by statements that the person is becoming hypnotized. A suggestion invites the person to experience some imaginary state of affairs as if it were real (e.g., “your hand is numb and insensitive, as if you were wearing a thick glove, and you can't feel much of anything through that glove.”). Typically, the patient or client is invited to experience the suggestion during the course of a hypnotic session. However, when the person is invited to experience a suggestion at some point after the hypnotic session has ended, it is referred to as a posthypnotic suggestion. The purpose of this article is to provide a comprehensive methodological review of controlled research on the efficacy of hypnosis for reducing labor and delivery pain. Over the last ten to fifteen years, a variety of reviews have been published on the use of hypnosis for pain associated with labor and delivery. Brown and Hammond (2007) reported a selective review of empirical research and case studies, emphasizing the effect of hypnosis on gestation at delivery, cessation of premature labor, and the health status of the neonate, rather than focusing on labor pain. Oster and Sauer (2000) described different approaches to hypnotic childbirth preparation and presented case studies. Finally, Cyna, McAuliffe, and Andrew (2004) conducted a meta-analysis of three randomized trials and concluded that hypnosis is effective in reducing the use of analgesics during labor. However, Cyna et al. do not provide an in-depth critique of methodological patterns in the entire body of controlled studies and do not include investigations published since 2004. To our knowledge, this article is the first comprehensive methodologically-informed review of all controlled research on the efficacy of hypnosis for managing labor pain. 1024 A.S. Landolt, L.S. Milling / Clinical Psychology Review 31 (2011) 1022–1031 versus supportive counseling; (c) hypnosis versus Lamaze; and (d) hypnosis versus childbirth education classes. 2. Method of review To be included in this review, studies were required to use a between-subjects or mixed model design in which a hypnosis intervention was compared with at least one alternative intervention, or a placebo, attention, standard care, or no-treatment control condition in reducing labor and delivery pain. An “alternative intervention” is defined as an established psychological or medical treatment for labor and delivery pain, such as epidural anesthesia. An “attention” control condition is defined as a minimal intervention lacking a significant amount of active treatment and is designed to control for the pain reducing effects of paying attention to a patient. No studies were included that failed to use pain as a dependent variable. Also, studies that did not report statistical tests of differences between comparison conditions were not included (e.g., Brann & Guzvica, 1987). An exhaustive search of the PsycINFO and PubMed databases, as well as an examination of related reviews in this area, identified 13 studies satisfying these criteria. Search terms included combinations of hypnosis, labor, delivery, pain, analgesia, interventions, and treatment outcomes. Table 1 summarizes the major characteristics of these studies, including sample size, treatment conditions, dependent measures of pain, and key findings. The studies can be organized based on the comparison condition into the following four groups: (a) hypnosis versus standard medical care; (b) hypnosis 3. Summary of controlled studies 3.1. Hypnosis versus standard medical care Several studies compared hypnosis with standard medical care in reducing the pain experienced by women during childbirth. While many women do seek childbirth education classes on their own, the reviewed studies comparing hypnosis with standard medical care did not report whether or not the mothers-to-be received childbirth education from an outside source. Education was not offered as an intervention during these studies, and only routine medical care was given. Cyna, Andrew, and McAuliffe (2006) evaluated the birth outcomes of women undergoing hypnotic preparation for labor and delivery pain in the obstetrics and gynecological service of an acute care teaching hospital in Australia. Seventy-seven primigravid (i.e., having a first baby) and parous (i.e., having given birth more than once) women self-selected to receive training in hypnosis. These individuals received up to four 40- to 60-minute training sessions after 35 weeks gestation. During the first session, these women were educated about hypnosis myths and were taught how to use hypnosis as an adjunct to other analgesia methods. In later sessions, they received suggestions Table 1 Characteristics of studies of hypnosis for managing labor pain. Study Sample Treatment conditions Pain measures Summary of key findings Cyna et al. (2006) 3326 women Epidural analgesia HP used epidurals less often than C VandeVusse et al. (2007) 101 women HP — Hypnotic preparation C — Std. med. care SH — Self-hypnosis C — Std. med. care Epidural analgesia; analgesic medication Jenkins and Pritchard (1993) 862 women SH — Self-hypnosis C — Std. med. care Analgesic medication Guthrie et al. (1984) 16 women Self rating of pain Rock et al. (1969) 40 women HH+ SH — Hetero-hypnosis plus self-hypnosis C — Std. med. care HH — Hetero-hypnosis C — Std. med. care SH used less analgesic medication, sedatives, and epidurals than C; SH had better Apgar scores than C SH used less analgesic medication and experienced shorter Stage 1 labor than C HH + SH reported less pain than C Letts et al. (1993) 495 women Epidural analgesia Martin et al. (2001) 42 adolescents 18 yrs or younger Mehl-Madrona (2004) 520 women Venn (1987) 122 women Freeman et al. (1986) 65 women Mairs (1995) 55 women Davidson (1962) 210 women Harmon et al. (1990) 60 women SH — Self-hypnosis SC — Supportive counseling C — Std. med. Care HP — Hypnotic preparation including posthypnotic suggestions SC — Supportive counseling HP — Hypnotic preparation SC — Supportive counseling C — Std. med. care HP — Hypnotic preparation including posthypnotic suggestions L — Lamaze LHP — L plus HP HP — Hypnotic preparation CE — Childbirth education classes SH — Self-hypnosis CE — Childbirth education classes SH — Self-hypnosis CE — Childbirth education classes C — Std. med. care SH — Self-hypnosis CE — Childbirth education classes Analgesic medication; resident rating of pain Analgesic medication HH used less analgesic medication and were rated as experiencing less pain than C SH used fewer epidurals than SC and C Analgesic medication; nurse and self ratings of pain HP had fewer birth complications and surgical interventions than SC; HP no different from SC in use of analgesic medication HP used less analgesic medication and epidurals than SC; SC did not differ from C HP no different from L or LHP in analgesic medication use or ratings of pain Epidural analgesia; self rating of pain HP no different from CE in pain reports or use of epidurals Analgesic medication and epidural analgesia; self rating of pain Analgesic medication SH reported less pain and anxiety than CE; SH no different from CE in analgesic use SH experienced shorter Stage 1 labor and used less analgesic medication than CE and C. Analgesic medication; self rating of pain SH used less analgesic medication, experienced shorter Stage 1 labor, and had higher Apgar scores than CE Epidural analgesia; analgesic medication A.S. Landolt, L.S. Milling / Clinical Psychology Review 31 (2011) 1022–1031 for pleasant imagery and relaxation, dissociation from the pain, analgesia, time distortion, and to experience contractions in a positive way. The hypnosis intervention was labeled as “self-hypnosis”, although it is unclear that expectant mothers were explicitly shown how to use self-hypnosis to re-experience the suggestions they had been given during training sessions. Participants in the hypnosis group were compared with a control group of 3249 women, matched for parity and gestational age, who had received standard medical care. Information on the control group was collected from retrospective chart data. Results showed that primigravid women who received hypnosis utilized epidural anesthesia significantly less frequently and had a decreased need for labor augmentation with oxytocics compared with controls. These findings suggest that hypnotic preparation may be effective for reducing epidural use during labor and delivery. VandeVusse, Irland, Berner, Fuller, and Adams (2007) conducted a retrospective chart review of one obstetrician's case load. All patients had given birth at a tertiary medical center located in a midwestern U.S. city. The hypnosis condition consisted of 50 participants who self-selected to receive self-hypnosis training during five sessions. The training sessions included basic information about hypnosis and instruction in the use of self-suggestions for pain management. The training sessions were provided either in group format by an obstetrician and clinical social worker, or in individual sessions by the physician or one of two clinical social workers. The control group, which only received standard medical care, was comprised of 51 participants who were parity and mode of delivery matched so that they resembled participants in the hypnosis group. Results showed that women receiving training in self-hypnosis were administered significantly fewer doses of analgesics and sedatives compared to women in the control group. Women in the hypnosis condition also received significantly fewer epidurals than those in the control condition. Finally, infants in the hypnosis condition had significantly better 1-minute Apgar scores than those in the control condition, although there were no differences in 5-minute Apgar scores. An Apgar score refers to a numerical rating of the infant's health made immediately after birth and ranging from 0 to 10, based on the following criteria: skin color, pulse rate, response to stimulation, muscle tone, and breathing. The study suggests the use of self-hypnosis may have benefits for both mothers and infants. Jenkins and Pritchard (1993) assessed the effects of self-hypnosis training on labor duration and analgesic use. The study was conducted in the maternity unit of a general hospital in Wales. Participants included 126 primigravid women and 300 age-matched controls, as well as 136 parous women and 300 age-matched controls. Participants in the hypnosis condition self-selected to receive six 30-minute training sessions provided by a medical hypnotherapist. These sessions focused on self-administered suggestions for analgesia and relaxation. The control group received standard medical treatment. Primigravid women in the self-hypnosis condition experienced significantly shorter Stage 1 and Stage 2 labor than women in the control group. Although parous women receiving self-hypnosis training experienced significantly shorter Stage 1 labor than controls, there was no difference in the length of Stage 2 labor. Compared with their controls, analgesic use was significantly reduced in both primigravid and parous women in the hypnosis condition. The study suggests that self-hypnosis may decrease analgesic use and shorten the length of labor, particularly in primigravid women. Guthrie, Taylor, and Defriend (1984) compared the experiences of mothers-to-be who utilized both self-hypnosis and hetero-hypnosis delivered by their husbands during labor with the experiences of mothers receiving routine medical care. The investigation was conducted in a teaching hospital located in Scotland. Eight women selfselected to participate in the hypnosis condition. The control group was comprised of eight women who matched the treatment group in terms of age, social class, parity, and length of labor. Women in the hypnosis 1025 condition and their husbands attended six to eight 30-minute training sessions, beginning at about 30 weeks of pregnancy. In the first sessions, a clinician taught the expectant mothers relaxation techniques and delivered suggestions for normality of pregnancy and delivery, diminished awareness of discomfort, satisfaction and pleasure of childbirth, and the ability of the participant's husband to relieve discomfort by stroking her abdomen. In later sessions, the clinician taught the expectant mothers to induce self-hypnosis and to have hypnosis induced by their husbands. Within 24 h of delivery, mothers were asked to rate the degree of pain experienced during labor. Women receiving hypnosis reported significantly less pain than those receiving standard medical care. However, there was no difference between the groups on childbirth satisfaction. Because husbands are not professional clinicians, the use of husbands as hypnotists may underestimate the potential benefits of hypnosis. Conceivably, even more pain reduction might have been achieved had professional clinical hypnotists performed hypnosis during labor. Finally, Rock, Shipley, and Campbell (1969) evaluated the effectiveness of hetero-hypnosis for reducing labor and delivery pain. Forty obstetrical patients at an urban university hospital located in major U.S. city were randomly assigned to either hypnosis or a standard medical care control condition. The hypnosis intervention was delivered by a medical student after the onset of labor and hospital admission. Hypnosis was induced by focusing on breathing, relaxation, and eye closure. Suggestions were given for glove anesthesia, which was transferred to the abdomen. Results showed that the hypnosis group required significantly smaller amounts of analgesic medications and rated the labor experience as significantly less painful than the control group. Also, patients in the hypnosis group were rated by medical staff as being significantly more comfortable at various points during the labor and delivery process. These results indicate that hetero-hypnosis provides more pain relief, including decreased epidural and analgesic use, during labor than standard medical care alone. Together, these studies suggest that hypnotic preparation (Cyna et al., 2006), self-hypnosis (Jenkins & Pritchard, 1993; VandeVusse et al., 2007), a combination of self-hypnosis and hetero-hypnosis delivered by husbands (Guthrie et al., 1984), and hetero-hypnosis delivered by medical staff (Rock et al., 1969) may be more effective than routine medical care in reducing pain and analgesic use during labor and delivery. However, because only one of these studies used random assignment to condition (Rock et al., 1969), the results should be considered promising rather than conclusive. 3.2. Hypnosis versus supportive counseling A small number of studies compared hypnosis with supportive counseling. Generally, the supportive counseling interventions used in the reviewed studies afforded expectant mothers with an opportunity to discuss pregnancy-related concerns and were intended to control for interpersonal contact and social support. Letts, Baker, Ruderman, and Kennedy (1993) evaluated whether the use of self-hypnosis led to the use of fewer obstetric interventions, more spontaneous deliveries, and greater satisfaction during delivery. Eighty-seven obstetric patients at a women's hospital located in a major Canadian city self-selected to receive hypnosis, while the supportive counseling group was comprised of fifty-six women who opted not to receive this training. Hypnosis participants attended two 90-minute training sessions at 32 and 34 weeks gestation in which they were instructed about the childbirth process and experienced verbal rehearsal of labor and delivery. These individuals were taught by a hypnotist how to use self-hypnosis to relax themselves and how to transfer glove anesthesia to the abdomen. The supportive counseling group was instructed about childbirth. Both groups were given care under the same physician. The hypnosis group was also 1026 A.S. Landolt, L.S. Milling / Clinical Psychology Review 31 (2011) 1022–1031 compared to a second control group of 352 patients delivered by another physician at the hospital. This group received only standard medical care. Compared to the supportive counseling and standard medical care groups, participants in the self-hypnosis group experienced significantly lower epidural rates. There was no difference between the self-hypnosis group and the control groups in patient satisfaction or spontaneous deliveries. Martin, Schauble, Rai, and Curry (2001) evaluated how hypnotic preparation incorporating posthypnotic suggestions affected labor and delivery in pregnant adolescents receiving prenatal care in the county public health department of a southern U.S city. Forty-two participants under the age of 18 were randomly assigned to one of two conditions. The hypnosis group received a four-session training sequence between 20 and 24 weeks gestation that included posthypnotic suggestions for a normal labor and delivery, feelings of comfort and confidence, an increased sense of control, and the ability to reenter hypnosis and to experience pleasant hypnotic imagery during a painful contraction (see Schauble, Werer, Rai, & Martin, 1998). However, the hypnosis group was not taught self-hypnosis and no direct intervention was made during labor and delivery. The hypnosis intervention was provided by a marriage and family therapist. The control group received supportive counseling, which provided an opportunity for patients to discuss issues of concern related to childbirth. Participants assigned to the hypnotic preparation condition had significantly shorter hospital stays, fewer birth complications, and fewer surgical interventions during delivery. However, there were no statistical differences between the hypnotic preparation and supportive counseling groups in the use of analgesic medication and admissions to the neonatal intensive care unit. Finally, Mehl-Madrona (2004) evaluated whether hypnosis could reduce birth complications and length of labor. Conducted over a tenyear period in three different U.S. states, the study examined 520 pregnant women who were still in either their first or second trimester. Participants were randomly assigned to hypnotic preparation with the author of the paper (a physician) or supportive psychotherapy with a female intern. The hypnosis intervention emphasized suggestions for diminished anxiety and fear, as well as increased feelings of relaxation, social support, and confidence in the ability to cope with the pain of labor. Visualization was used to guide the woman through an imaginary experience of giving birth. However, it is unclear whether hypnosis participants received formal posthypnotic suggestions or training in self-hypnosis. Unquestionably, there was no direct intervention during labor and delivery. The supportive psychotherapy treatment involved discussions of issues related to pregnancy. A no-treatment control group was matched to women in the supportive psychotherapy group based on age, parity, socioeconomic status, race, and birth risk status. Results showed that women in the hypnotic preparation group experienced fewer complicated deliveries and cesarean sections than those in the supportive psychotherapy and no-treatment control groups. Also, the hypnotic preparation group used oxytocin, epidural anesthesia, and analgesics less frequently. The lack of differences between the supportive psychotherapy and the no-treatment groups suggests that supportive psychotherapy was ineffective. Studies comparing hypnosis and supportive counseling provide mixed results. While Letts et al. (1993) and Mehl-Madrona (2004) reported benefits of hypnosis in reducing analgesic medication use, Martin et al. (2001) did not. However, the findings of Martin et al. (2001) do not disqualify hypnosis. Similar to Mehl-Madrona (2004), Martin et al. (2001) found that hypnotic preparation was associated with fewer birth complications and surgical interventions. Of note, confidence in the findings of both Mehl-Madrona (2004) and Martin et al. (2001) is strengthened by the use of random assignment to condition. In general, these studies argue that hypnosis may be more effective than supportive counseling. Because supportive counseling was used as an attention-control group in these studies, the results suggest that hypnosis is effective due to factors that go beyond the attention that patients received from the hypnotists. 3.3. Hypnosis versus Lamaze Lamaze is a specialized form of preparation that emphasizes natural childbirth methods as an alternative to the use of medical intervention. It involves cognitive restructuring of the women's perceptions of childbirth by focusing on confidence-building and educating mothers-to-be about anatomy and the process of giving birth (Lowe & Frey, 1983). Lamaze often involves the use of a coach and teaches breathing and relaxation exercises. Venn (1987) assessed whether a combination of Lamaze and hypnosis reduced pain and enhanced satisfaction more than either method alone. Participants were 122 patients at a U.S. Naval hospital who self-selected into one of three conditions: Lamaze-only, hypnosis-only, or Lamaze-plus-hypnosis. Women in the hypnosis conditions received hypnotic preparation for childbirth beginning in the third trimester of pregnancy, which incorporated Erickson's (1966) interspersal induction of analgesia. They also experienced age progression through the birth experience, posthypnotic suggestions to re-enter hypnosis during labor and delivery, and guided imagery to achieve analgesia by walking into a pool of cold water. Hypnotically prepared individuals did not receive formal training in self-hypnosis, nor was there any direct intervention during labor. Results showed that there was no difference between the three interventions on patient ratings of pain and satisfaction with the delivery process, nurse ratings of pain, and analgesic medication use. To measure hypnotic suggestibility, the Stanford Hypnotic Clinical Scale for Adults was administered to women in the hypnosis conditions, but these scores were not significantly correlated with the outcome measures. Because there was no difference between the three interventions on any of the outcome measures, and in the absence of a no-treatment control condition, the findings can best be described as inconclusive. 3.4. Hypnosis versus childbirth education classes Childbirth education classes provide women with information about labor, birth, and coping strategies for emotional distress and pain (Spiby, Slade, Escott, Henderson, & Fraser, 2003). These classes often teach breathing and relaxation techniques and discuss various positions for the expectant mother to assume to increase comfort during the first stage of labor. Women participating in childbirth education classes generally experience greater benefits during labor than women who have not taken these classes (Harmon, Hynan, & Tyre, 1990). A number of studies compared hypnosis with childbirth education classes in decreasing the pain experienced by women during labor and delivery. Freeman, Macaulay, Eve, and Chamberlain (1986) assessed the effect of hypnotic preparation on pain, satisfaction and analgesic requirements for primigravid women. Participants were randomly assigned to one of two conditions. A hypnotic preparation group of twenty-nine individuals received hypnotic suggestions for relaxation and pain relief in weekly individual sessions beginning at 32 weeks gestation. It is unclear whether these individuals were formally instructed in self-hypnosis, but they were encouraged to imagine warmth or anesthesia in one hand and shown how to transfer these feelings to the abdomen. There was no direct intervention during labor and delivery. A comparison group of thirty-six participants attended weekly childbirth education classes. Results showed there was no difference between women receiving hypnotic preparation and those attending childbirth education classes in terms of the proportion given epidural anesthesia or on reports of pain relief. Women in the hypnotic preparation group who scored in the high and medium ranges of hypnotic suggestibility based on the A.S. Landolt, L.S. Milling / Clinical Psychology Review 31 (2011) 1022–1031 Stanford Hypnotic Clinical Scale utilized epidurals less frequently than those scoring in the low range. However, women in the childbirth education group were not tested to determine hypnotic suggestibility and formal moderator analyses were not undertaken. In sum, the results of this study suggest that hypnotic preparation is no more effective than traditional childbirth education classes in reducing labor and delivery pain. Mairs (1995) measured the differences in experiences of pain and anxiety during childbirth between 55 primigravid women who either received self-hypnosis training or attended childbirth education classes at a city hospital in Northern Ireland. Expectant mothers who self-selected into the hypnosis group attended four sessions, beginning between 26 and 37 weeks of gestation. In the first session, hypnosis was explained and induced using eye closure, and deepened via progressive relaxation and imagery. In the remaining sessions, participants practiced transferring numbness and experiencing laborappropriate imagery suggestions. The comparison group attended routine childbirth education classes. Although there were no significant differences between the groups in terms of drug usage, self-hypnosis participants reported significantly less pain and anxiety during labor. Davidson (1962) assessed the effects of self-hypnosis on the duration and need for medication during labor. Participants selfselected into one of three groups: self-hypnosis, physiotherapy (i.e., childbirth education classes), and a no-treatment control group. Although a choice was given, patients who were older, anxious about giving birth, or had had distressing labors were encouraged to join the hypnosis group. Each condition consisted of 45 primigravid and 25 parous women. The self-hypnosis participants attended six sessions at the hospital in groups of six, beginning early in pregnancy and ending as close to giving birth as possible. Hypnosis was explained and then induced through eye-fixation and progressive relaxation. Suggestions were given for a normal labor experience, decreased awareness of pain, and decreased need for analgesics. Participants were taught to induce selfhypnosis in the third session. The hypnosis intervention was provided by an obstetrician. The physiotherapy group received six weekly classes beginning in the 34th week of gestation. These classes focused on relaxation, controlled breathing, and pelvic exercises. The control group received no special childbirth training. Women in the self-hypnosis condition experienced a significantly shorter Stage 1 labor and required significantly less analgesic medication than women in the childbirth education and control conditions. The author contends that the relaxation and lessening of fear that occurs as a result of hypnotic training may result in a quicker and less painful dilation of the cervix, making the overall experience of labor faster and less painful. Finally, Harmon et al. (1990) examined the benefits of using selfhypnosis in conjunction with traditional childbirth education classes. Participants were 60 patients at an obstetrical private practice group located in a midwestern U.S. state. At the end of the second trimester of pregnancy, these patients were assessed for hypnotic suggestibility using the Harvard Group Scale of Hypnotic Susceptibility, Form A. These women were then randomly assigned to receive either childbirth education classes or a combination of these classes and training in self-hypnosis. Each of the two intervention groups was then subdivided based on high and low suggestibility scores. At the start of each session participants in the hypnosis condition received a hypnotic induction and suggestions for relaxation, enjoyment of childbirth, heaviness of muscles, labor as an enjoyable experience, numbness in parts of the body, and postpartum wellness delivered by a psychologist. The childbirth education group practiced muscle relaxation exercises and techniques for effortless breathing. The women participated in groups of 15 during six one-hour weekly sessions at the same hospital. All participants were given an opportunity to practice the techniques they had learned by using 1027 them to reduce ischemic pain. Furthermore, participants were given training audio tapes and instructed to practice with the tapes daily. Results indicated that adding self-hypnosis training to childbirth education classes produced shorter Stage 1 labor, but did not affect Stage 2 labor. Self-hypnosis also resulted in the use of less medication during labor and higher infant Apgar scores. Contrary to expectation, there was no interaction between treatment condition and suggestibility level. The results suggest that self-hypnosis is a useful addition to traditional childbirth education classes. In sum, the findings of these studies point to the effectiveness of hypnosis as an addition to traditional childbirth education classes. Although Freeman et al. (1986) failed to show significant benefits for hypnotic preparation, the use of self-hypnosis was associated with less pain (Mairs, 1995) and decreased medication use (Davidson, 1962; Harmon et al., 1990) than childbirth education classes. Of note, Harmon et al., which was distinguished by the use of random assignment to condition, reported other benefits for self-hypnosis relative to traditional childbirth education classes, including shorter Stage 1 labor and higher infant Apgar scores. 4. Methodological considerations Before forming conclusions about the efficacy of hypnosis as an intervention for labor and delivery pain, it is necessary to examine the methodological limitations of this body of research. Table 2 evaluates the 13 reviewed studies against six key methodological criteria: a) random assignment; b) specification of sample; c) use of a treatment manual; d) intervention delivered in hypnotic context; e) active use of hypnosis during labor and delivery; and f) analysis of hypnotic suggestibility. Studies that satisfied the criteria listed in Table 2 are indicated by “Yes”, while those that do not satisfy the criteria are denoted by “No.” In a few instances, the status of a criterion was not obvious; these cases are marked as “Unclear.” 4.1. Random assignment The use of random assignment to condition is critical to sound treatment outcome research. Without random assignment, there is an increased risk that observed differences between treatment conditions are due to variables other than the treatments themselves. Despite this, a major limitation evident in this literature was a failure to utilize random assignment, with only five of 13 studies employing it (Freeman et al., 1986; Harmon et al., 1990; Martin et al., 2001; Mehl-Madrona, 2004; Rock et al., 1969). Because potential confounding variables were not nullified through random assignment in eight investigations, it is possible that extraneous variables accounted for reported differences in pain reduction in those studies. Indeed, in the eight studies that did not use random assignment, participants self-selected to receive hypnosis. These eight studies obtained more supportive results than studies in which participants were randomly assigned to condition. Specifically, in the five studies using random assignment, two (40%) found no differences in pain reduction between hypnosis and the comparison conditions (Freeman et al., 1986; Martin et al., 2001). In contrast, in the eight studies where participants self-selected into condition, only one (13%) failed to show a difference in pain reduction between hypnosis and the comparison condition (Venn, 1987). A likely reason that participants self-selected to receive hypnosis is because they had a positive attitude toward it — and those who refused hypnosis had a negative attitude. Having a positive attitude toward hypnosis has been shown to be associated with higher hypnotic suggestibility (Spanos, Brett, Menary, & Cross, 1987) and better hypnotic treatment outcomes (Schoenberger, Kirsch, Gearan, Montgomery, & Pastyrnak, 1997). It is therefore possible that studies which used self-selection into condition overestimated the effectiveness of hypnosis for relieving labor and delivery pain. 1028 A.S. Landolt, L.S. Milling / Clinical Psychology Review 31 (2011) 1022–1031 Table 2 Methodological criteria. Study Random assignment Specification of sample Treatment manual Treatment in hypnotic context Active use of hypnosis Hypnotic suggestibility as moderator Cyna et al. (2006) VandeVusse et al. (2007) Jenkins and Pritchard (1993) Guthrie et al. (1984) Rock et al. (1969) Letts et al. (1993) Martin et al. (2001) Mehl-Madrona (2004) Venn (1987) Freeman et al. (1986) Mairs (1995) Davidson (1962) Harmon et al. (1990) No No No No Yes No Yes Yes No Yes No No Yes No Yes No No No No No No Yes No No No Yes No No No No No No No No No No No No No Yes Yes Yes Yes No Yes Yes Yes Yes Unclear Yes Yes Yes No Unclear Unclear Unclear Yes Unclear No No No No Unclear Unclear Unclear No No No No No No No No Yes Yes No No Yes 4.2. Specification of sample Specifying the age, sex, and racial characteristics of the sample used in a treatment outcome study is necessary in order to determine the population to which the findings generalize. Although it is clear that participants in the reviewed studies consisted of women in their child-bearing years, only three of the fourteen studies identified the race of participants (Harmon et al., 1990; VandeVusse et al., 2007; Venn, 1987). These three studies focused primarily on white females. Because cultural influences play a role in the perception of pain, women from other ethnic groups may respond differently to labor and delivery than white women (Leeman et al., 2003; Woodrow, Friedman, Siegelaub, & Collen, 1972). As such, the samples used in these three studies are not representative of the population of all child-bearing women. Moreover, the lack of specification of race in the other 10 studies makes it is impossible to determine how well the results of those investigations generalize to the population of all childbearing females. 4.3. Treatment manual A valuable practice in psychotherapy outcome research involves using a treatment manual. A manual operationalizes the treatments and promotes consistency when different experimenters deliver the interventions within a single study. A manual also allows the study to be accurately replicated by other research teams. Without a treatment manual, it is difficult to replicate a study and verify its results. Hypnosis is a complicated procedure and can be used in a variety of ways for managing pain, including suggestions for analgesia, time distortion, amnesia, dissociation, pain displacement and transformation, reinterpretation of the experience, and distraction to pleasant imagery, to name just a few (see Patterson & Jensen, 2003). Thus, the label “hypnosis” is a generic term that encompasses many different suggestions and techniques. Unfortunately, none of the 13 reviewed studies specified the nature of the interventions by using a treatment manual. 4.4. Hypnotic context Hypnosis scholars generally agree that the social context in which a hypnotic suggestion is delivered has at least some impact on the resulting response (Kirsch & Lynn, 1995). For example, relabeling a cognitive-behavioral intervention as hypnosis can significantly enhance its effectiveness (see Kirsch, Montgomery, & Sapirstein, 1995). In 11 of the 13 reviewed studies, it seemed clear to us that participants knew that they were receiving hypnosis. However, in two studies it was not obvious that participants understood they were being hypnotized (Freeman et al., 1986; Rock et al., 1969). This may have reduced the effectiveness of hypnosis in those two investigations. Indeed, Freeman et al. reported that hypnosis was no more effective than childbirth preparation classes in reducing labor and delivery pain. Until empirical research shows that establishing a hypnotic context has no impact on the effectiveness of hypnosis for reducing labor and delivery pain, researchers should strive to clearly communicate to participants that the hypnosis intervention actually involves “hypnosis”. 4.5. Active use of hypnosis Of the 13 reviewed studies, in only one was it obvious to us that the hypnosis intervention was used during labor and delivery. Rock et al. (1969) reported that hetero-hypnosis resulted in less pain and analgesic medication use than standard medical care. In seven of the reviewed studies, it was unclear to us whether the hypnosis intervention was used during labor. These studies involved either explicit training for mothers-to-be in self-hypnosis (Davidson, 1962; Harmon et al., 1990; Jenkins & Pritchard, 1993; Letts et al., 1993; Mairs, 1995; VandeVusse et al., 2007) or a combination of selfhypnosis training and hetero-hypnosis (Guthrie et al., 1984). All seven of these studies reported a positive effect for hypnosis on some indicator of pain. Finally, in five of the reviewed studies, it seemed likely that hypnosis was not actively used during labor and delivery. In three of the five studies, expectant mothers underwent hypnotic experiences during training sessions (i.e., hypnotic preparation), but apparently were not explicitly shown how to use self-hypnosis during labor and delivery (Cyna et al., 2006; Freeman et al., 1986; Mehl-Madrona, 2004). Two studies paired hypnotic preparation with posthypnotic suggestions for pain relief (Martin et al., 2001; Venn, 1987). Of the five studies using some form of hypnotic preparation, only two reported a positive effect for hypnosis on pain. Cyna et al. (2006) found that hypnotically prepared women used epidurals less often than those receiving standard medical care. Mehl-Madrona (2004) observed that hypnotic preparation was more effective than supportive counseling or standard medical care in reducing the use of analgesic medications and epidurals. Of note, including posthypnotic suggestions in the hypnotic preparation did not help to make it a significantly more effective intervention than supportive counseling (Martin et al., 2001) or Lamaze (Venn, 1987). Some research has shown that when a hypnotic suggestion for pain reduction is delivered continuously throughout a pain stimulus, it produces more relief than when the suggestion is given once at the outset of the pain (Price & Barber, 1987). Similarly, the findings of the reviewed studies suggest that when hypnosis could be experienced throughout labor in the form of either hetero-hypnosis or selfhypnosis, it consistently had a beneficial effect on pain. However, when hypnosis was administered only in advance of the labor process, as is characteristic of hypnotic preparation, the benefits were far less consistent. A.S. Landolt, L.S. Milling / Clinical Psychology Review 31 (2011) 1022–1031 4.6. Hypnotic suggestibility Hypnotic suggestibility is a trait-like individual difference variable reflecting the general tendency to respond to hypnosis and hypnotic suggestions (Gur, 1978/1979). Suggestibility can be measured with standardized scales consisting of a hypnotic induction and a series of test suggestions. Lynn and Shindler (2002) recommend assessing hypnotic suggestibility whenever hypnosis is used as a treatment. A metaanalysis on the effectiveness of hypnotic analgesia by Montgomery, DuHamel, and Redd (2000) suggests the value of doing so. This metaanalysis found that the average person treated with hypnosis experienced more pain relief than 75% of individuals in no-treatment and standard care control conditions. However, the analgesic effect of hypnosis varied dramatically according to suggestibility level. The average effect size was D = 1.16 for participants in the high range of suggestibility, D = 0.64 for those in the medium range, and only D = −0.01 for those in the low range. That is, hypnosis had virtually no analgesic effect for individuals of low suggestibility. Of the 13 studies reviewed herein, only three assessed hypnotic suggestibility with a standardized scale. Of these three studies, only one examined the statistical association between suggestibility and treatment condition. Somewhat surprisingly, Harmon et al. (1990) did not find a significant interaction between hypnotic suggestibility and treatment condition. However, women scoring in the high range of suggestibility reduced pain more than those falling in the low range. More research is needed on the relationship between hypnotic suggestibility and the effectiveness of hypnosis for reducing labor pain. We would like to echo the recommendation of Lynn and Shindler (2002). Future studies of the effectiveness of hypnosis for managing labor pain should measure hypnotic suggestibility using a standardized scale and perform appropriate moderator analyses (see Baron & Kenny, 1986). Of course, this will only be meaningful if researchers also randomly assign participants to treatment condition. If participants are allowed to self-select into treatment condition, those scoring in the high range of suggestibility may be overrepresented in hypnosis condition and those scoring in the low range overrepresented in the comparison conditions. 4.7. Other methodological considerations A word is in order regarding the nature of the dependent measures of pain used in this literature. Self-report measures provide an index of a patient's pain perception. A visual analog scale in which the patient rates pain intensity along a 0–10 scale is an example. Observational measures provide an index of a patient's pain behavior (e.g., moaning, crying). The use of analgesic medication and epidural anesthesia provides a biological indicator of pain. Self-report, observational and biological indicators offer complimentary information. However, only one of the 13 reviewed studies tapped all three channels of measurement (Venn, 1987). By far, utilization of analgesic medication and epidural anesthesia was the most commonly employed measure of pain; only one study failed to tap the biological channel of measurement (Guthrie et al., 1984). Five studies used a self-report pain measure (Freeman et al., 1986; Guthrie et al., 1984; Harmon et al., 1990; Mairs, 1995; Venn, 1987) and two studies used an observational measure (Rock et al., 1969; Venn, 1987). However, of these investigations, only one study employed a well-established self-report or observational measure of pain. Specifically, Harmon et al. used the McGill Pain Questionnaire (Melzack, 1975), a reliable and valid self-report measure of pain perception. In contrast, studies in which patients or observers (e.g., nurses, attending physicians) made a single global rating of pain are likely to have produced results that are unreliable. Similarly, if a long period of time passed since the end of delivery, self-report measures may have provided a distorted indicator of the effects of treatment. Research has 1029 shown that people have difficulty remembering the intensity of a pain stimulus and that self-reports of the analgesic effects of treatment tend to increase with the passage of time (Price et al., 1999). In the future, researchers are encouraged to utilize reliable and valid measures of pain that tap all three channels of measurement. 5. Discussion Our comprehensive review of 13 controlled studies suggests that hypnosis holds promise as an intervention for managing labor and delivery pain. Hypnosis was shown to be more effective than standard medical care (Cyna et al., 2006; Guthrie et al., 1984; Jenkins & Pritchard, 1993; Rock et al., 1969; VandeVusse et al., 2007), supportive counseling (Letts et al., 1993; Mehl-Madrona, 2004), and traditional childbirth education classes (Davidson, 1962; Harmon et al., 1990; Mairs, 1995). Just two studies comparing hypnosis with supportive counseling (Martin et al., 2001) and childbirth education classes (Freeman et al., 1986) failed to show a positive effect for hypnosis on at least one indicator of pain. Our conclusions are consistent with those of a recent general review of hypnotic analgesia by Stoelb, Molton, Jensen, and Patterson (2009), who observed that hypnosis tends to outperform standard medical care and interventions that are non-hypnotic in nature in relieving pain. In addition to reducing reports of pain, as well as the use of analgesic medications and epidural anesthesia, hypnosis was found to have other benefits for expectant mothers and their infants. The administration of hypnosis was associated with better infant Apgar scores (Harmon et al., 1990; VandeVusse et al., 2007), as well as shorter Stage 1 labor (Davidson, 1962; Harmon et al., 1990; Jenkins & Pritchard, 1993). This latter finding is noteworthy because it is during Stage 1 labor that women experience very painful uterine contractions and often request pain medication (Harms, 2004). A clear pattern emerged when considering the nature of the hypnotic interventions used in these studies. Hetero-hypnosis (Rock et al., 1969), self-hypnosis (Davidson, 1962; Harmon et al., 1990; Jenkins & Pritchard, 1993; Letts et al., 1993; Mairs, 1995; VandeVusse et al., 2007), and a combination of hetero-hypnosis with self-hypnosis (Guthrie et al., 1984) were consistently found to be more effective than comparison conditions in alleviating pain. There were no studies contradicting this pattern. However, only 2 of the 5 studies evaluating hypnotic preparation were able to show that it was significantly more effective than a comparison condition in reducing some indicator of pain (Cyna et al., 2006; Mehl-Madrona, 2004). This pattern suggests that hypnosis may be more effective if it is experienced during the actual labor process, either in the form of self-hypnosis or heterohypnosis. Although we contend that hypnosis holds promise as an intervention for labor pain, it is not possible for us to reach a more definitive conclusion regarding its efficacy. This is because only five of the 13 reviewed studies utilized random assignment to condition. In the other 8 studies, participants were allowed to self-select into treatment condition, which likely produced findings overestimating the effectiveness of hypnosis. Considering only the five studies that used random assignment, three yielded a positive effect for hypnosis on pain. Rock et al. (1969) showed that hetero-hypnosis was more effective than standard medical care in reducing pain and use of analgesic medication. Harmon et al. (1990) found that self-hypnosis was more effective than childbirth education classes in reducing analgesic medication use. Mehl-Madrona (2004) reported that hypnotic preparation was more effective than supportive counseling and standard medical care in reducing the use of analgesic medication and epidurals. The two studies using random assignment that failed to show a positive effect for hypnosis on some indicator of pain both used hypnotic preparation as the intervention (Freeman et al., 1986; Martin et al., 2001). 1030 A.S. Landolt, L.S. Milling / Clinical Psychology Review 31 (2011) 1022–1031 Consequently, based primarily on the studies employing random assignment, and using the other studies only as supportive evidence, it seems reasonable to conclude that both hetero-hypnosis and selfhypnosis show considerable promise as interventions for managing labor and delivery pain. The evidence regarding hypnotic preparation was less encouraging. These observations may have important clinical implications. Clinicians who provide hypnosis to expectant mothers may wish to consider the benefits of designing their interventions in a way which maximizes the likelihood that hypnosis will be used during the actual labor and delivery process. This can be accomplished by having the clinician administer hypnosis to expectant mothers during labor or by explicitly teaching women how to do self-hypnosis so that they can administer hypnosis to themselves during labor. However, simply providing expectant mothers with hypnotic experiences during training sessions appears to be of limited value. Also, it is unclear that adding posthypnotic suggestions to these training experiences is likely to make hypnotic preparation effective. The failure to use random assign to condition was a widespread methodological limitation in this body of research. Other common limitations included a failure to use a treatment manual and to specify the demographic characteristics of samples. Future studies of the efficacy of hypnosis for managing labor pain should strive to randomly assign participants to condition, describe the age and race characteristics of samples, as well as clearly operationalize the hypnosis and comparison interventions by incorporating them in a manual. A growing emphasis on evidence-based practice (American Psychological Association Presidential Task Force on Evidence-Based Practice, 2006) and continuing interest in empirically supported therapies (Chambless & Hollon, 1998; Task Force on Promotion and Dissemination of Psychological Procedures, 1995) suggest the importance of doing so. Random assignment, sample specification, and use of a treatment manual are explicit criteria for evaluating studies with the goal of identifying a psychological therapy as empirically supported for a particular problem and population (Chambless & Hollon, 1998). In turn, identifying an intervention as an empirically supported therapy is one way of establishing evidence-based practice. A previous review identified a failure to blind participants to treatment condition as a limitation of this literature (see Cyna et al., 2004). Blinding participants would be important in a drug study where the researcher is interested in separating the chemical effects of a medication from the effects of what participants think about the drug. Accordingly, blinding participants is a key component of a placebo-controlled drug study. However, blinding participants is counterproductive in the study of a psychological therapy like hypnosis, where a person's thoughts about the nature of the therapy are integral to its psychological mechanism of action. Along these lines, prominent social psychological theories of hypnotic responding such as role theory (Sarbin, 1950), compliance with demand characteristics (Wagstaff, 1991), and response expectancies (Kirsch, 1990) all share the premise that believing one is being hypnotized is what leads to profound alterations in behavior. Indeed, in a meta-analysis of 18 studies, Kirsch et al. (1995) showed that cognitive-behavioral therapies for a variety of symptoms and problems could be enhanced simply by relabeling and reframing them as “hypnosis.” Thus, communicating to participants that they are receiving hypnosis is a desirable feature in studies of the efficacy of hypnosis for managing labor pain — not a limitation. Fortunately, 11 of the 13 studies included in our review clearly established a hypnotic context for participants and researchers are encouraged to continue this practice. 6. Conclusions Childbirth ranks among the most universal of human experiences. However, the pain associated with labor and delivery can be very distressing and many women describe it as severe or extremely severe (Melzack, 1993). Although pharmacologic methods such as analgesic medications and epidurals have proven to be effective for reducing the discomfort of labor and delivery, there are risks associated with their use (Anim-Somuah et al., 2005; Simpson & Creehan, 2008; Thorp & Breedlove, 1996). Fearing these side effects, many expectant mothers voice reservations about pharmacologic analgesia (Van den Bussche, Crombez, Eccleston, & Sullivan, 2007). Our review suggests that hypnosis shows considerable promise as an adjunct to pharmacologic methods of managing labor pain. Heterohypnosis and self-hypnosis were consistently shown to be more effective than standard medical care, supportive counseling, and childbirth education classes. However, additional controlled trials, emphasizing random assignment to condition, specification of study samples, and the use of treatment manuals, are needed to establish hetero-hypnosis and self-hypnosis as empirically supported therapies for managing labor pain. There is a substantial amount of scientifically sound research on the effectiveness of hypnosis for treating a range of clinical pain problems, such as burn pain and cancer-related pain (see Montgomery et al., 2000; Patterson & Jensen, 2003; Stoelb et al., 2009). Unfortunately, studies of the use of hypnosis for reducing labor and delivery pain have lagged behind these other areas in terms of quality. There is no reason for this to be so. In some ways, research on the effectiveness of hypnosis for managing labor and delivery pain represents an underexplored area of inquiry. Consequently, we look forward to the proliferation of methodologically sound research evaluating this promising, but unproven intervention for labor and delivery pain. References⁎ American Psychological Association Presidential Task Force on Evidence-Based Practice (2006). Evidence-based practice in psychology. American Psychologist, 61, 271–285. Anim-Somuah, M., Smyth, R. M. D., & Howell, C. J. (2005). Epidural versus non-epidural or no analgesia in labour. Cochrane Database of Systematic Reviews, 4, 1–81. Baron, R. M., & Kenny, D. A. (1986). The moderator–mediator variable distinction in social psychological research: Conceptual, strategic, and statistical considerations. Journal of Personality and Social Psychology, 51, 1173–1182. Brann, L. R., & Guzvica, S. R. (1987). Comparison of hypnosis with conventional relaxation for antenatal and intrapartum use: A feasibility study in general practice. The Journal of the Royal College of General Practitioners, 37, 437–440. Brown, D., & Hammond, D. (2007). Evidence-based clinical hypnosis for obstetrics, labor and delivery, and preterm labor. International Journal of Clinical and Experimental Hypnosis, 55, 355–371. Chambless, D. L., & Hollon, S. D. (1998). Defining empirically supported therapies. Journal of Consulting and Clinical Psychology, 66, 7–18. Creasy, R. K., Resnik, R., & Iams, J. D. (2004). Maternal–fetal medicine: Principles and practice (5th edition). Philadelphia, PA: W.B. Saunders Co. *Cyna, A. M., Andrew, M. I., & McAuliffe, G. L. (2006). Antenatal self-hypnosis for labor and childbirth: A pilot study. Anesthesia Intensive Care, 34, 464–469. Cyna, A. M., McAuliffe, G. L., & Andrew, M. I. (2004). Hypnosis for pain relief in labour and childbirth: A systematic review. British Journal of Anaesthesia, 93, 505–511. *Davidson, J. A. (1962). An assessment of the value of hypnosis in pregnancy and labour. British Medical Journal, 2, 951–953. Erickson, M. H. (1966). The interspersal hypnotic technique for symptom correction and pain control. American Journal of Clinical Hypnosis, 8, 198–209. *Freeman, R. M., Macaulay, A. J., Eve, L., & Chamberlain, G. V. P. (1986). Randomised trial of self hypnosis for analgesia in labour. British Medical Journal, 292, 657–658. Gur, R. C. (1978–1979). Measuring hypnotic susceptibility: A guest editorial. American Journal of Clinical Hypnosis, 21, 64–66. *Guthrie, K., Taylor, D. J., & Defriend, D. (1984). Maternal hypnosis induced by husbands. Journal of Obststrics and Gynaecology, 5, 93–96. *Harmon, T., Hynan, M., & Tyre, T. (1990). Improved obstetric outcomes using hypnotic analgesia and skill mastery combined with childbirth education. Journal of Consulting and Clinical Psychology, 58, 525–530. Harms, R. W. (2004). Mayo clinic guide to a healthy pregnancy. New York, NY: Harper Resource. Hilgard, E. R. (1965). Hypnotic susceptibility. New York, NY: Harcourt, Brace & World. *Jenkins, M. W., & Pritchard, M. H. (1993). Hypnosis: Practical applications and theoretical considerations in normal labour. British Journal of Obstetrics and Gynaecology, 100, 221–226. Kirsch, I. (1990). Changing expectations: A key to effective psychotherapy. Belmont, CA: Brooks/Cole. Kirsch, I. (1994). Defining hypnosis for the public. Contemporary Hypnosis, 11, 142–143. ⁎ (References marked with an asterisk indicate studies included in review.). A.S. Landolt, L.S. Milling / Clinical Psychology Review 31 (2011) 1022–1031 Kirsch, I., & Lynn, S. J. (1995). The altered state of hypnosis: Changes in the theoretical landscape. American Psychologist, 50, 846–858. Kirsch, I., Montgomery, G., & Sapirstein, G. (1995). Hypnosis as an adjunct to cognitivebehavioral psychotherapy: A meta-analysis. Journal of Consulting and Clinical Psychology, 63, 214–220. Leeman, L., Fontaine, P., King, V., Klein, M. C., & Ratcliffe, S. (2003). The nature and management of labor pain: Part I. Nonpharmacologic pain relief. American Academy of Family Physicians, 68, 1109–1112. *Letts, P. J., Baker, P. R. A., Ruderman, J., & Kennedy, K. (1993). The use of hypnosis in labor and delivery: A preliminary study. Journal of Women's Health, 2, 335–341. Littleton, L. Y., & Engebretson, J. (2004). Maternity nursing care (1st ed.). Albany, NY: Delmar. Lowe, R., & Frey, J. (1983). Predicting Lamaze childbirth intentions and outcomes: An extension of the theory of reasoned action to a joint outcome. Basic and Applied Social Psychology, 4, 353–372. Lynn, S. J., & Shindler, K. (2002). The role of hypnotizability assessment in treatment. American Journal of Clinical Hypnosis, 44, 185–197. *Mairs, D. (1995). Hypnosis and pain in childbirth. Contemporary Hypnosis, 12, 111–118. *Martin, A., Schauble, P., Rai, S., & Curry, R. (2001). The effects of hypnosis on the labor processes and birth outcomes of pregnant adolescents. Journal of Family Practice, 50, 441–443. *Mehl-Madrona, L. (2004). Hypnosis to facilitate uncomplicated birth. American Journal of Clinical Hypnosis, 46, 299–312. Melzack, R. (1975). The McGill Pain Questionnaire: Major properties and scoring methods. Pain, 1, 277–299. Melzack, R. (1993). Labour pain as a model of acute pain. Pain, 53, 117–120. Montgomery, G. H., DuHamel, K. N., & Redd, W. H. (2000). A meta-analysis of hypnotically induced analgesia: How effective is hypnosis? International Journal of Clinical and Experimental Hypnosis, 48, 138–153. Niven, C., & Murphy-Black, T. (2000). Memory for labor pain: A review of the literature. Birth: Issues in Perinatal Care, 27, 244–253. Oster, M. I., & Sauer, C. P. (2000). Hypnotic methods for preparing for childbirth. In L. M. Hornyak & J. P. Green (Eds.), Healing from within: The use of hypnosis in women's health care (pp. 161–190). Washington, DC: American Psychological Association. Patterson, D., & Jensen, M. (2003). Hypnosis and clinical pain. Psychological Bulletin, 129, 495–521. Pillitteri, A. (2009). Maternal and child health nursing: Care of the childbearing and childrearing family (6th ed.). Baltimore, MD: Lippincott William & Wilkins. Price, D. D., & Barber, J. (1987). An analysis of factors that contribute to the efficacy of hypnotic analgesia. Journal of Abnormal Psychology, 96, 46–51. Price, D. D., Milling, L. S., Kirsch, I., Duff, A., Montgomery, G. H., & Nicholls, S. S. (1999). An analysis of factors that contribute to the magnitude of placebo analgesia in an experimental paradigm. Pain, 83, 147–156. 1031 *Rock, N., Shipley, T., & Campbell, C. (1969). Hypnosis with untrained, nonvolunteer patients in labor. International Journal of Clinical and Experimental Hypnosis, 17, 25–36. Sarbin, T. R. (1950). Contributions to role taking theory: 1. Hypnotic behavior. Psychological Review, 57, 225–270. Schauble, P. G., Werer, W. E. F., Rai, S. H., & Martin, A. (1998). Childbirth preparation through hypnosis: The hypnoreflexogenous reflex. American Journal of Clinical Hypnosis, 40, 273–283. Schoenberger, N. E., Kirsch, I., Gearan, P., Montgomery, G., & Pastyrnak, S. L. (1997). Hypnotic enhancement of a cognitive behavioral treatment for public speaking anxiety. Behavior Therapy, 28, 127–140. Simkin, P. (2000). Commentary: The meaning of labor pain. Birth: Issues in Perinatal Care, 27, 254–255. Simpson, K. R., & Creehan, P. A. (2008). AWHONN's perinatal nursing (3rd ed.). Philadelphia, PA: Lippincott Williams & Wilkins. Spanos, N. P., Brett, P. J., Menary, E. P., & Cross, W. P. (1987). A measure of attitudes toward hypnosis: Relationships with absorption and hypnotic susceptibility. American Journal of Clinical Hypnosis, 30, 139–150. Spiby, H., Slade, P., Escott, D., Henderson, B., & Fraser, R. (2003). Selected coping strategies in labor: An investigation of women's experiences. Birth: Issues in Perinatal Care, 30, 189–194. Stoelb, B., Molton, I., Jensen, M., & Patterson, D. (2009). The efficacy of hypnotic analgesia in adults: A review of the literature. Contemporary Hypnosis, 26, 24–39. Task Force on Promotion and Dissemination of Psychological Procedures (1995). Training in and dissemination of empirically validated psychological treatments: Reports and recommendations. Clinical Psychologist, 48, 3–23. Thorp, J. A., & Breedlove, G. (1996). Epidural analgesia in labour: An evaluation of risks and benefits. Birth, 23, 63–83. Van den Bussche, E., Crombez, G., Eccleston, C., & Sullivan, M. J. L. (2007). Why women prefer epidural analgesia during childbirth: The role of beliefs about epidural analgesia and pain catastrophizing. European Journal of Pain, 11, 275–282. *VandeVusse, L., Irland, J., Berner, M., Fuller, S., & Adams, D. (2007). Hypnosis for childbirth: A retrospective comparative analysis of outcomes in one obstetrician's practice. American Journal of Clinical Hypnosis, 50, 109–119. *Venn, J. (1987). Hypnosis and Lamaze method — An exploratory study: A brief communication. International Journal of Clinical and Experimental Hypnosis, 35, 79–82. Wagstaff, G. F. (1991). Hypnosis, compliance, and belief. New York, NY: St. Martin's Press. Waldenström, U., Bergman, V., & Vasell, G. (1996). The complexity of labor pain: Experiences of 278 women. Journal of Psychosomatic Obstetrics and Gynecology, 17, 215–228. Woodrow, K. M., Friedman, G. D., Siegelaub, A. B., & Collen, M. F. (1972). Pain tolerance: Differences according to age, sex, and race. Psychosomatic Medicine, 34, 548–556.