Download the timing of the transition to nicotine dependence

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Note: Sentences marked in bold complement the text of the full article’s Method section.
Auxiliary Materials
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Sample
The data are from The Transition to Nicotine Dependence (TND) study, a prospective
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five-wave longitudinal household study of a multi-ethnic cohort of 1,039 6th-10th graders
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selected from the Chicago Public Schools (CPS) and one of their parents. A two-stage design
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was implemented to select the target sample for the follow-up. In Phase I (spring 2003), 15,763
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students in grades 6-10 were sampled from 43 public schools in the CPS. The sample
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(N=1,039) was designed to provide approximately equal numbers of adolescents among the
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three major ethnic groups: non-Hispanic white (N=272), non-Hispanic African American
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(N=343), and Hispanic (N=424). Because of the ethnic distribution in the CPS, largely
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Hispanic schools were excluded and schools with large numbers of non-Hispanic white
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students were oversampled. The resulting sample is representative of each racial/ethnic
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group from the CPS, except for Hispanics from largely Hispanic high schools and whites
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with Polish speaking parents. Schools were divided into eight segments and the survey
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administration was staggered over four months. The survey completion rate was 83.1%. A
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target sample of 1,236 youths was selected: 1,106 tobacco users who started to use tobacco in the
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prior 12 months and 130 non-tobacco users susceptible of starting to smoke, divided among non-
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Hispanic whites, non-Hispanic African Americans and Hispanics. Susceptible non-tobacco users
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satisfied 2 of 3 criteria as per Pierce et al.41: (a) might try smoking a cigarette soon; (b) did not
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answer “definitely not” to whether would smoke if a friend offered them a cigarette; or (c) will
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be smoking cigarettes in one year. Sensitivity and specificity of these criteria for predicting
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the onset of smoking among a sample of baseline adolescent never smokers four years later
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were 66.7% and 61.9%, respectively.41 Non-tobacco users were included as targets in the
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household sample so as to not have to indicate to parents that their child was a tobacco user when
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requesting active parental consent for child participation. Whites and African Americans who
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had started to use tobacco 0-12 months earlier and Hispanics who had started 0-6 months
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earlier were selected with certainty; Hispanics who started 7-12 months earlier were
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sampled at a 25% rate, because of the larger number of Hispanics than other race/ethnic
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groups in the sample schools. The onset of tobacco use was based on a question that asked
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students “How long has it been since you FIRST tried or used a tobacco product?” The
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coded responses ranged from “I first tried within the last 3 months, 4-6 months ago, 7-12,
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13-18, 19-24 and more than 24 months ago.” Of the tobacco users in the school survey
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(N=4,363), 1,623 (37.2%) reported having started to use within the last 12 months; 1,106
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were selected for the target sample. Another 751 (17.2%) reported having started 13-24
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earlier and 1,989 (45.6%) started more than 24 months earlier. Youths who initiated
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tobacco use within the last 12 months or 13-24 months earlier were older at onset and
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lighter users than those who initiated tobacco use more than 24 months earlier. At onset,
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those who initiated tobacco use within the last 12 months were on average 12.2 years old
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(S.D.=2.1), those who initiated 13-24 months earlier were 12.3 years old (S.D.=1.8), and
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those who initiated 24 months earlier were 10.7 years old (S.D.=2.0). Of these three groups,
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13.6%, 19.2% and 25.2%, respectively, had ever smoked more than 25 cigarettes.
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In Phase II, on average 9 weeks after each school survey, 1,039 youths (84.1% of 1,236
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target) (272 white, 343 African American, 424 Hispanic) and one parent (86.8% mothers)
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participated in the two year (2003-2005) longitudinal follow-up consisting of three annual 90
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minute computerized household interviews with youths and parents (W1, W3, W5), and two 20
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minute bi-annual interviews with youths six months after W1 and W3 (W2, W4). Of the 1,039
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youths, 922 were tobacco users (832 smokers); and 117 were non-tobacco users susceptible of
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starting to smoke. Completion rates at W2-W5 were 96.0% of the W1 sample. The National
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Opinion Research Center (NORC), at the University of Chicago, conducted the fieldwork. In
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902 (86.8%) families, mothers were the participating parent (870 biological, 21 adoptive, 11
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step or foster); 58 respondents were fathers; 79 were other parental figures, such as
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grandmothers. Hispanics who had started to use tobacco 7-12 months earlier were given a
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weight of 4, since they were sampled at the rate of 25%. All Hispanic tobacco users were
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rescaled to the unweighted number who were interviewed.
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Human subject procedures
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Passive parental consent was obtained for the school survey and active consent for the
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household interviews; adolescent assent was obtained for both administrations. Interviewers
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emphasized that all answers would be confidential. All procedures were approved by the
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Institutional Review Boards of the New York State Psychiatric Institute, Columbia University,
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and NORC.
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Data collection: Overview
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Selected DSM-IV child psychiatric disorders were ascertained at W1, W3 and W5 from
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youths and mothers. Youths reported at every wave about their smoking, other tobacco use and
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DSM-IV nicotine dependence symptoms, and annually about their use and DSM-IV abuse and
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dependence symptoms for other substances, novelty seeking, and exposure to smoking siblings
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and peers. Mothers reported annually on their smoking, DSM-IV nicotine dependence
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symptoms, DSM-IV depression, and delinquency.
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Definitions of variables
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Variables were measured from youths (Y), and from parents (P) about themselves or the
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youths. Predictor variables were measured by W3, outcome variables by W5. The highest
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values reported by each time period was selected.
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(Y-P) Psychiatric disorders: Measured by the NIMH Diagnostic Interview Schedule for
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Children (DISC-IV-Y and -P).42 Mood disorders (major depressive disorder (MDD) and
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dysthymia (DYS) were assessed at W1, W3 and W5; anxiety disorders (social phobia, panic,
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generalized anxiety, post-traumatic stress (PTSD)), and disruptive behavior disorders (attention-
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deficit hyperactivity (ADHD), oppositional defiant (ODD), conduct disorder (CD)) at W3 and
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W5. Each disorder was ascertained from parents and youths, except ADHD (parents only). For
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each disorder, lifetime and last 12 month symptoms were asked at the first assessment; last 12
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months symptoms were asked at subsequent assessments. For DYS and PTSD, only last 12
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month symptoms were asked at all assessments. Scoring that combined criteria from parent and
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child reports without impairment was used.43 Due to human subjects concerns, questions
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about current suicidal ideation and prior suicide attempt were removed from W1 major
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depressive disorder (MDD), and forced sex from CD. The suicide-related items were
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reinstated at W3 and W5, when a clinical psychologist was available to provide a mental
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health consultation, if needed. The diagnostic scoring was modified slightly for MDD at
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W1 and was based on meeting 4 of 8 rather than 5 of 9 criteria. The modified definition
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yielded a slightly higher rate of last 12 month MDD (4.5%) than the standard definition
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used at W3 (3.3%). Thus, the mood disorder variable based on the modified W1 MDD
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definition may yield a slightly higher rate of disorder than the standard definition. The
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scoring for CD was not modified and meeting 3 of 15 criteria was retained (Dr. Prudence
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Fisher, personal communication, 10/31/07).
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(Y-P) Onset ages of psychiatric disorders: (Not available for PTSD). The earliest age reported
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by parent or youth for a specific disorder defined onset age for the class. Onset age for CD is
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not ascertained for the diagnosis but rather for each positive symptom. Thus, for youths
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who met diagnostic criteria for CD, the earliest age of a positive symptom determined the
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onset age for the disorder.
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(Y) Nicotine dependence: Measured as per the Diagnostic and Statistical Manual of Mental
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Disorder (DSM-IV)44 by an instrument developed for adolescents.45 The 11-item scale measured
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symptoms in the last 12 months that define the seven DSM-IV dependence criteria:44 tolerance,
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withdrawal, impaired control, unsuccessful attempts to quit, great deal of time spent using,
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neglect important activities, and use despite physical or psychological problems (α=.85). For
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the measurement of the seven DSM-IV dependence criteria, four criteria were indexed by
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two alternate symptoms and three were indexed by a single symptom. The criteria of
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withdrawal asked about 12 specific symptoms; 3 were sham items included to check the
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reliability of responses. These 3 items and a fourth item about craving were excluded from
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the scoring of withdrawal (α=.92). The withdrawal criterion was met when respondents
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reported at least 4 of the 8 valid symptoms. Full dependence was defined when 3 criteria were
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met.
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(Y) Onset age of first nicotine dependence criterion: Month/year of first criterion minus birth
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date.
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(Y) Onset age of full nicotine dependence: Month/year of third criterion minus birth date.
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(Y) Onset age of cigarette use: Month/year first used cigarettes minus birth date.
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(Y) Initial sensitivity first tobacco use:46 Experiences associated with first tobacco use. Two
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scales averaged the scores of component items: pleasant symptoms (pleasant sensations,
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relaxation, pleasurable dizziness, pleasurable rush/buzz (α=.71)); unpleasant symptoms
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(unpleasant sensations, nausea, unpleasurable dizziness, unpleasurable rush/buzz, coughing,
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heart pounding, headache, bad taste (α=.78)). Each symptom coded 1=none to 4=intense
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experience.
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(Y) Lifetime smoking: At W1, ever smoked a cigarette, even a puff; at subsequent waves,
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smoked since the prior interview.
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(Y) Number cigarettes smoked lifetime: Recoded to mid-point: smoked one or more puffs but
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never a whole cigarette=.5; 1 cigarette=1; 2-5 cigarettes=3; 6-15=10; 16-25=20; 26-99=62; and
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100+=100 cigarettes
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(Y) Other tobacco use lifetime (smokeless, cigars, pipes, bidis, kreteks).
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(Y) Alcohol use and abuse/dependence lifetime: Combined ever used and DSM-IV abuse or
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dependence on alcohol, ascertained by the DISC-IV-Y: never used alcohol; used but no
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abuse/dependence; lifetime alcohol abuse/dependence.
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(Y) Alcohol, marijuana and other illicit substance use and abuse/dependence lifetime:
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Combined ever used and DSM-IV abuse or dependence on alcohol, marijuana or any other illicit
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drug (OID), ascertained by the DISC-IV-Y: never used alcohol, marijuana or OID; used but no
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abuse/dependence; lifetime alcohol, marijuana or OID abuse/dependence.
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(Y) Perceived peer smoking: At least one friend currently smoked.
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(Y) Perceived siblings’ smoking: Sibling ever smoked.
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(P) Parent smoking/nicotine dependence lifetime: Combined ever smoked and DSM-IV nicotine
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dependence, measured by the same scale as for the youths (α=.80): never smoked; smoked but
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no dependence; lifetime nicotine dependence.
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(P) Parent lifetime depression: DSM-IV major depressive disorder as per the Composite
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International Diagnostic Interview (CIDI 2.1).
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(P) Parent lifetime delinquency: Count of 11 delinquent activities (range 0-11; α=.89):
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damaging property, injuring persons, shoplifting, stealing something worth < or > $50,
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breaking into house/building, threatening with weapon, fighting with another/group,
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driving car without owner’s permission, and getting into trouble with police. Scored
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highest value at W1 or W3.
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(Y) Youth novelty seeking: Based on Cloninger’s Tridimensional Personality Questionnaire.47
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Average of 9 five-point items (α=0.80): try things for fun, look for something exciting, can
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get people to believe lies, do things based on how feel at the moment, get excited and lose
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control, like when people do whatever they want, follow instincts, can stretch the truth and
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change interests a lot. The response alternatives were 1=not at all true; 2=a little true;
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3=somewhat true; 4=pretty true; 5=very true. Scored highest value at W1 or W3.
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(Y) Age: in years.
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(Y) Race/ethnicity: non-Hispanic white; non-Hispanic African American; Hispanic.
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(Y) Gender
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Participants and non-participants in household interviews
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Participants (N=1,039) and non-participants (N=197) in the household interviews
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were compared on sociodemographic characteristics and school reports of smoking and
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depressive symptoms. Non-participants did not differ on age or gender; however, a higher
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proportion of non-Hispanic whites than non-Hispanic African Americans declined to
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participate. Non-participants were more likely than participants to report having ever
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smoked (92.8% vs. 85.0%, p<0.01), having smoked more extensively (11.1% versus 6.3%
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had ever smoked 100 or more cigarettes, p<0.05), and having met criteria for DSM-IV
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nicotine dependence (31.1% versus 24.4%), although this difference was not statistically
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significant. Non-participants did not differ from participants on depressive symptoms.
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Inconsistencies in reporting of tobacco use
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There were discrepancies between the school and household reports of tobacco
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use.56 Of the youths who had reported any tobacco use in school (N=922), 213 denied at the
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Wave 1 household interview having ever used tobacco; of those who reported in school
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smoking cigarettes (N=832), 189 denied having ever smoked at Wave 1. There were
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further discrepancies in the age of tobacco use onset. In the household interviews,
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adolescents were asked the specific date (month, year) of first use of each tobacco product
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ever used. Time since onset was calculated as the difference between the earliest date of
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use of any product and the interview date. Only 281 (39.6%) of the 709 adolescents who
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had reported in school having started using tobacco in the prior 12 months were identified
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as having started to use within the prior year based on the more precise (month/year of
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onset) ascertainment in the household interviews; 428 were estimated to have started to
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smoke more than one year before Wave 1. Of these, 75 started within 12 months prior to
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the school survey but more than 12 months prior to the household interview because of the
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time lag between the two data collections. Those who denied having used tobacco in the
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household interviews were, according to their school reports, younger, more likely to be
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African Americans, lighter smokers and less likely to meet criteria for the full DSM
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dependence syndrome than those who admitted use in the household. The youths (N=353),
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who in the household were estimated to have started using tobacco more than a year prior
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to the household interview even though they had been selected because they had reported
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in the school having started to use tobacco within the prior 12 months, were more likely to
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be males, African Americans, heavier smokers and to have experienced more DSM-IV
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dependence symptoms than those who were correctly assessed as having started using
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tobacco within the prior 12 months. The group (N=75) who no longer fell within the 12
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month interval because of the time lag between the school and household data collections
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did not differ from those correctly classified. Thus, those who denied having used tobacco
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in the household were lighter users than those who admitted use. By contrast, those who
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were reclassified as having started to use more than 12 months earlier were heavier users
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than those who remained classified as having started within the last 12 months. The
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cumulative impact of non-participation and inconsistent reporting resulted in a sample that
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was biased towards the exclusion of tobacco users, especially heavier users.
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Analytical samples for current study
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Five analytical samples were defined as of W3: (1) Total cross-sectional sample
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(N=1,039) to provide background descriptive information about the prevalence of smoking,
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nicotine dependence, and psychiatric disorders in the cohort; (2) longitudinal sample of lifetime
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smokers without nicotine dependence symptoms as of W3 (N=419) to examine psychiatric
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disorders as predictors of the onset of nicotine dependence by W5; (3-5) three longitudinal
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samples of lifetime smokers without a lifetime diagnosis of an anxiety (N=686), mood (N=636),
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or disruptive (N=580) disorder as of W3 to examine nicotine dependence as a predictor of the
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onset of each psychiatric disorder by W5.
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Statistical analysis
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Logistic regressions were estimated to identify the prospective associations between (1)
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psychiatric disorders and onset of nicotine dependence, and (2) nicotine dependence and onset of
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psychiatric disorders. The outcome variable for onset of dependence was meeting at least one
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criterion by W5. The three outcome variables for onset of psychiatric disorders by W5 were
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meeting last 12 month DSM-IV criteria for any anxiety, mood, or disruptive disorder,
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respectively. Multivariate analyses controlled for comorbidity among psychiatric disorders;
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smoking history (age of smoking onset, initial sensitivity to tobacco, quantity smoked lifetime,
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other tobacco use lifetime); other substance use (alcohol, marijuana and OID use and
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abuse/dependence); peer and sibling smoking; novelty seeking; parental nicotine dependence,
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depression and delinquency. To the extent possible, identical covariates were included across all
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models. Smoking history covariates were included in models predicting psychiatric disorder
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since they may have unique effects over those of dependence. Selected two-way interaction
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effects were tested to examine if the impact of predictors for each outcome were moderated by
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gender or race/ethnicity. All analyses were weighted and conducted in SAS® V9.1.
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To control for Type I errors in univariate analyses, the Holm’s procedure48, a modified
Bonferroni approach, was applied to conceptually related groups of variables. Groups of
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variables for Table 1 included: (1) anxiety disorders (social phobia, panic, generalized
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anxiety, post-traumatic stress, any anxiety); (2) mood disorders (major depression,
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dysthymia, any mood); (3) disruptive disorders (attention deficit, oppositional defiant,
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conduct, any disruptive); and (4) smoking/dependence (ever smoked, and 1+ and 3+ nicotine
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dependence criteria); and for Tables 2 and 3 (1) sociodemographics (age, gender,
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race/ethnicity); (2) psychiatric disorders (anxiety, mood, disruptive), smoking/tobacco
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history (onset age of smoking, initial positive and negative sensitivity to tobacco, quantity
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smoked, other tobacco use, and nicotine dependence (for Table 3 only), exposure to
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smoking in the proximate social environment (peer, sibling, parental smoking), parental
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psychopathology (depression and delinquency). Three variables, any psychiatric disorder
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(Tables 1-2), alcohol, marijuana or OID use and abuse/dependence and novelty seeking
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(Tables 2-3) were treated individually. For each main effect, the p values for each group of
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variables were ordered from smallest to largest. The p value was compared to the
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significance level .05/(k - i + 1), where k = the number of main effects tested in each
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variable grouping, and for k main effects, i = 1,2,…, k. For example, in Table 1, for anxiety
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disorder, five main effects for gender were tested. Post traumatic stress was accepted
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because its p value was less than .05/(5 - 1 + 1) = .01, and any anxiety disorder because its p
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value was less than .05/(5 – 2 + 1)=.0125.
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Appendix Table A presents the distributions of covariates for the four longitudinal samples.
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