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Chapter 17
Anxiety Disorders, Autistic
Disorder, ADHD, and Stress
Disorders
Anxiety Disorders
• A psychological disorder characterized by tension, overactivity of the
ANS, expectation of an impending disaster, and continuous
vigilance for danger
• Two types of anxiety disorders that appear to have biological
causes:
– Panic disorder
– Obsessive-compulsive disorder (OCD)
Anxiety Disorders
• Panic disorder
– Characterized by episodic periods of symptoms such as
shortness of breath, irregularities in heartbeat, and other
autonomic symptoms, accompanied by intense fear
– Onset in young adulthood
– Victim often feels that he or she is going to die
– Between panic attacks, people with panic disorder suffer from
anticipatory anxiety, the fear that another panic attack will strike
– Anticipatory anxiety often leads to agoraphobia, fear of being
away from home or other protected places
– Disorder appears to be hereditary
– Strange genetic association between “loose joints” and panic
disorder
• Patients with joint hypermobility syndrome are more likely to also
have panic disorder than control subjects
Anxiety Disorders
• Panic disorder
– Previously treated with a combo of behavior therapy and a
benzodiazepine (which have strong anxiolytic, or anxiety reducing,
effects)
• Benzodiazepine receptors are located on the GABAA receptor complex
• When benzo binds with receptor, it increases the sensitivity of the GABA
binding site and produces an anxiolytic effect
• Anxiety disorders may be caused by decreased number of benzo receptors
– SSRI’s used to treat panic disorder and OCD
– Cingulate, prefrontal, and anterior temporal cortices are involved (esp.
decrease in activity during panic attacks)
Anxiety Disorders
• Obsessive compulsive disorder (OCD)
– Suffer from obsessions (an unwanted thought or idea with which a
person is preoccupied) and compulsions (the feeling that one is obliged
to perform a behavior, even if one prefers not to do so)
– Incidence is 1-2% of population; females > males; most commonly
begins in young adulthood
– Compulsions fall into 4 categories: counting, checking, cleaning,
avoidance
– Some investigators believe that the compulsive behaviors are forms of
species-typical behaviors (e.g. grooming, cleaning, and attention to
sources of potential danger) that are released from normal control
mechanisms by a brain dysfunction
– Could also be pathological examples of social rituals
Anxiety Disorders
• OCD (con’t)
– May have genetic origin
– OCD is associated with Tourette’s syndrome (a neurological disorder
characterized by tics and involuntary vocalizations and sometimes by
compulsive uttering of obscenities and repetitions of the utterances of
others) that appears in childhood
• Treatment for Tourette’s includes antischizophrenic meds that block DA D2
receptors
– Many patients that have OCD have tics, and many patients with
Tourette’s have obsessions and compulsions
– Both disorders may be produced by the same genotype
– However, some brain damage (esp. to basal ganglia, cingulate gyrus,
and prefrontal cortex) may lead to development of OCD
Anxiety Disorders
• OCD (con’t)
– Tic disorders ca be caused by a streptococcal infection, that can
damage brain tissue
• Esp. by damage to basal ganglia
– Increased activity in frontal lobes and caudate nucleus in patients
with OCD
– Some patients with severe OCD have been treated with
cingulotomy (surgical destruction of the cingulum bundle, which
connects the prefrontal cortex with the limbic system)
• Helps reduce intense anxiety and the symptoms of OCD
– Direct pathway (excitatory) in basal ganglia – symptoms of OCD
may be a result of overactivity in this pathway
– Most effective therapy for OCD is drug therapy
• All 5-HT reuptake blockers
Autistic disorder
• 4 in every 10,000 infants born with this disorder
• A chronic disorder whose symptoms include failure to develop
normal social relations with other people, impaired
development of communicative ability, lack of imaginative
ability, and repetitive, stereotyped movements
• Afflicts boys 3x more than girls
• Most autistic people are mentally retarded, but not all are
• Autistic disorder is one of several pervasive developmental
disorders that have similar symptoms
– Asperger’s syndrome – less severe, do not include language
impairment or cognitive deficits
– Rett’s disorder – genetic disorder seen in girls; accompanies and
arrest of normal brain development during infancy
– Childhood disintegrative disorder – show normal social and
intellectual develop. until begin to regress sometime b/t ages 210 yrs.
Autistic disorder
• Autism includes affective, cognitive and behavioral abnormalities
• Some investigators suggest that this may stem from brain
abnormalities that prevent the person from forming a “Theory of
mind” (i.e. unable to predict and explain the behavior of other
humans in terms of their mental states)
• Imaging studies show great decrease in activity of fusiform face area
(region of brain responsible for face recognition) in autistic
individuals while looking at pictures of faces
Autistic disorder
• Possible causes
– Heritability
•
•
•
•
Some forms appear to be heritable
2-3% of siblings of autistic people also have autism
Concordance rate for monozygotic twins is ~70%
May be associated with specific genetic disorders: Phenylketonuria
(PKU) – caused by inherited lack of an enzyme that converts
phenylalanine (amino acid in diet) into tyrosine; buildup of
phenylalanine can cause disruption in brain development, and
sometimes autism
– Brain pathology
• ~20% of all cases of autism have definable biological causes, such
as rubella, prenatal thalidomide, encephalitis, etc.
• Can result from a wide variety of factors that damage the brain or
impair its development
• Thalidomide (a drug given to pregnant women in 1960s to treat
morning sickness) caused serious birth defects
Attention-Deficit/Hyperactivity
Disorder (ADHD)
• A disorder characterized by uninhibited responses, lack of sustained
attention, and hyperactivity
• First shows itself in childhood
• Usually discovered at school
• DSMIV requires the presence of 6 or more of 9 symptoms to
diagnose
– e.g. difficulty in sustaining attention in tasks of play activities; easily
distracted by extraneous stimuli
• Diagnosis is often difficult
• Most common treatment is methylphenidate (Ritalin), which inhibits
reuptake of DA
Attention-Deficit/Hyperactivity
Disorder (ADHD)
• Possible causes
– Strong evidence for hereditary factors in a person’s likelihood of
developing ADHD
– Symptoms may be a result of a “delay of reinforcement gradient” (i.e.
the longer the delay of some type of reinforcement for a behavior, the
less effective that reinforcement is)
– May be caused by underactivity of DA transmission
• Results from human and animal studies contradict each other; not clear
whether ADHD is caused by excessive number of DA transporters
– Imaging studies showed decreased blood volume in basal ganglia and
cerebellar vermis of boys with ADHD
Stress Disorders
• Stress – a general, imprecise term that can refer either to a stress
response or to a stressor
– Stressor – a stimulus (or situation) that produces a stress response
– Stress response – a physiological reaction caused by the perception of
aversive or threatening situations
• The physiological responses that accompany the neg. emotions
prepare us to threaten rivals or fight them or to run away
– Fight-or-flight response – a species-typical response preparatory to
fighting or fleeing; thought to be responsible for sme of the deleterious
effects of stressful situations on health
Stress Disorders
•
Physiology of the stress response
– Autonomic and endocrine responses to emotions: sympathetic branch of
ANS becomes active, and adrenal glands secrete epinephrine, NE and
steroid stress hormones
– Epinephrine affects glucose metabolism, causing nutrients stored in
muscles to become available to provide energy for strenuous exercise
– Some of the behavioral and physiological responses produced by
aversive stimuli appear to be mediated by NE neurons
– The other stress-related hormone is cortisol, a glucocorticoid (a hormone
that has effects on metabolism) secreted by the adrenal cortex
– Secretion of glucocorticoids is controlled by paraventricular nucleus of the
hypothalamus (PVN)
• The neurons of the PVN secrete a peptide called corticotropin-releasing
hormone (CRH) which stimulates the anterior pituitary to secrete
adrenocorticotropic hormone (ACTH), which enters the bloodstream and
stimulates the adrenal cortex to secrete glucocorticoids
Stress Disorders
• Health effects of long-term stress
– Many studies of humans who have been subjected to stressful
situations have found evidence of ill health
– Hans Selye, a pioneer in the study of stress, suggested that most of
these harmful effects from stress were produced by prolonged secretion
of glucocorticoids
• Effects include increased blood pressure, damage to muscle tissue, steroid
diabetes, etc.
• Research with animals shows that long-term exposure to glucocorticoids
destroys neurons in field CA1 of hippocampus, affecting memory in the longterm
• Severe stress appears to cause brain damage in humans as well
Stress Disorders
• Posttraumatic Stress Disorder (PTSD)
– A psychological disorder caused by exposure to a situation of
extreme danger and stress
– Symptoms include recurrent dreams or recollections
– Can interfere with social activities and cause a feeling of
hopelessness
– Genetic factors play a role in a person’s susceptibility to develop
PTSD and to be involved in an event that may cause PTSD
– Found hippocampal damage in patients with PTSD
– However, found lower levels of cortisol, instead of assumed
higher levels (in order to cause brain damage)
• Exposure to stress increases the number and sensitivity of
glucocorticoid receptors in the hypothalamus and anterior pituitary
• Instead, high levels of CRH may play a role in the development of
PTSD
Stress Disorders
• Stress and cardiovascular disease
– The degree to which people react to potential stressors may
affect the likelihood that they will suffer from cardiovascular
disease
– Individuals who had hyperreacted to a stress test earlier in life
were more likely to have high blood pressure later in life
– Studies with monkeys demonstrate that individual differences in
emotional reactivity are a risk factor for cardiovascular disease
• The animals that showed strongest negative reactions to a threat
eventually developed higher rates of coronary artery disease
– Acute stress can also affect cardiovascular disease
• Can cause constriction of coronary arteries, arrhythmias in
heartbeat, stimulation of platelet function (causes forming of clots),
and increased viscosity of the blood
Stress Disorders
• The coping response
– One of the most important variables that determines whether an
aversive stimuli will cause a stress reaction is the degree to which the
stimulus can be controlled
– Animals can learn coping responses in order to avoid aversive stimuli,
and thus reduce their stress response
– The opportunity to make a coping response decreases the negative
impact of stress on the hippocmpus
Stress Disorders
• Psychoneuroimmunology
– Stress response can impair the function of the immune system
– Study of interactions b/t the immune system and behavior is
called psychoneuroimmunology
– The immune system
• Function is to protect us from infection
• 2 types of reactions occur when the body is invaded by foreign
organisms:
– Chemically mediated: involves antibodies (proteins produced to seek out
and destroy antigens present on invading organisms)
» One type of antibody is released into circulation by B-lymphocytes,
which develop in bone marrow; the antibodies released are called
immunoglobulins, which are chains of proteins that help destroy
invading microorganisms
– Cell mediated: produced by T-lymphocytes, white blood cells that
originate in thymus gland
– Communication b/t cells is accomplished by cytokines
Stress Disorders
• Psychoneuroimmunology
– Neural control of the immune system
• Stress increases the secretion of glucocorticoids, and these hormones
directly suppress the activity of the immune system
• Individuals with severe stress showed lowered levels of antibodies
• This suppression is largely mediated by glucocorticoids, which are mediated
by neural activity
– Stress and infectious disease
• Stress-producing events can increase a person’s susceptibility to illness
• Since the immune system is suppressed, a person is more likely to develop
an illness after times of stress