Chapter Fifteen Psychological Disorders

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Chapter FifteenPsychological Disorders
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Substance Abuse

• Substance abuse is a maladaptive pattern of
  substance use that leads to clinically
  significant impairment or distress
• Dopamine and reinforcement
• rats will press lever up to 2000 times per hour
  for stimulation of certain brain areas that
  release dopamine
• many events also stimulate the release of
  dopamine, e.g., sexual activity and video games
• nearly all addicting drugs increase dopamine
  release in the nucleus accumbens
• attractive female faces, but not attractive male
  faces, also activated nucleus accumbens in
  heterosexual men

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• Figure 15.2 Location of the nucleus accumbens in
  the human brain. A wide variety of procedures
  that yield reinforcement inhibit the activity of
  the nucleus accumbens. Therefore this area is
  considered essential for reinforcement or reward.

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Drugs and Reinforcement

• But, a reinforcer can be anything that causes you
  to repeat the behavior, e.g., studying for test
  or any unexpected pleasant event
• Drug ibogaine reduces reinforcement values of
  drugs (and most other reinforcers) in nucleus
  accumbens
• but, cravings last long after last drug use and
  reminders will trigger new cravings, e.g.,
  cigarettes

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Stimulant Drugs

• Amphetamine increases release of dopamine from
  presynaptic terminals
• causes cell to excrete more instead of
  reabsorbing
• also blocks certain synapses that inhibit release
• Cocaine blocks reuptake of dopamine,
  norepinephrine and serotonin, prolonging effects
• user develops tolerance after repeated use due to
  buildup of dynorphin which counteracts cocaine
  reinforcement
• but, habit continues even with weak reinforcement
• Effects of amphetamine and cocaine lasts only a
  few hours and user crashes into depressed state

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Stimulant Drugs cont.

• Methlyphenidate (Ritalin) often prescribed for
  ADD
• blocks reuptake just like cocaine
• but, dosages are small and in pill form to
  gradually increase and decline, preventing
  addiction
• also increases serotonin which has calming effect
• research with rats found that use in juveniles
  led to avoidance in adulthood

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Stimulant Drugs cont.

• Drugs that increase activity at dopamine synapses
  decrease overall activity of brain
• but, drug reduces background noise so that
  stimuli are more arousing
• Repeated use leads to long lasting changes in
  brain metabolism and blood flow
• increases risk of stroke, epilepsy, and memory

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Stimulant Drugs cont.

• MDMA (ecstasy) releases dopamine in low doses and
  serotonin in higher doses
• damaged dopamine and serotonin axons in monkeys
• may increase later risk of depression and
  Parkinsons disease
• people show normal levels of serotonin one year
  after quitting, but had low performance on memory
  tests
• but most switched to marijuana so difficult to
  interpret

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Stimulant Drugs cont.

• Nicotine
• stimulates nicotinic receptors which are abundant
  on dopamine receptors in the nucleus accumbens
• stimulates dopamine release
• and, like cocaine, repeated use reduces dopamine
  response to reinforcement
• person may find it helpful to take antidepressant
  when quitting

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Opiates

• Morphine, heroin, and methadone are derived from
  opium poppy
• highly additive but not when used as medical
  painkillers
• relaxes user and decreases pain by acting on
  receptors in the brain
• body produces endorphins that act on same
  receptors to reduce pain
• also increases dopamine by inhibiting GABA, a
  dopamine inhibitor
• blocks release of norepinephrine to reduce stress
  and decrease memory storage

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Marijuana Plants

• Leaves of plant contain TCH and other related
  cannaboids which intensify sensory experience
• few receptors in medulla and brain stem so
  breathing and heart rate not affected
• used to relieve pain, nausea and glaucoma
• users experience memory impairments but may
  recover 4 weeks after use
• use facilitates LTD effect and weakens otherwise
  normal memory connections
• mice without receptors fail to extinguish learned
  connections

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Marijuana Plants cont.

• Cannaboid receptors limit release of both
  excitatory and inhibitory neurotransmitters
• use reduces effects of stroke in animals by
  limiting both neurotransmitters
• Mice without receptors in hypothalamus fail to
  increase appetite after food deprivation
• explains appetite increase in users
• Mice under marijuana influence press bar sooner
  for scheduled reinforcement
• act as though passage of time had slowed down, a
  common report among users

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Hallucinogenic Drugs

• Hallucinogenic drugs, like LSD, that distort
  perception
• LSD stimulates serotonin receptors at
  inappropriate times for longer than normal
  duration
• even after damage to releasing neurons,
  postsynaptic neurons increase receptors making
  LSD more effective
• but, not clear why user experiences hallucinations

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Alcohol and Alcoholism

• Most widely used recreational drug in the world
• Alcoholism when alcohol interferes with the
  persons life
• Many effects
• inhibits flow of sodium across cell membrane and
  expands membrane
• decreases serotonin activity
• facilitates response by the GABAA receptor
• blocks glutamate receptors
• increases dopamine activity

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Type 1 (or Type A) Alcoholism

• Later onset (usually after 25)
• Gradual onset
• Fewer genetic relatives with alcoholism
• Men and women about equally
• Generally less severe

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Type 2 (or Type B) Alcoholism

• Earlier onset (usually before 25)
• More rapid onset
• More genetic relatives with alcoholism
• Men far more than women
• Often severe, often associated with criminality
• Genetic Basis
• low serotonin turnover and impulsive behavior
  have genetic basis
• concordance rates in MZ twins is .55
• children have increased risk

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Alcohol Metabolism and Antabuse

• Antabuse (disulfiram) is moderately effective in
  treating alcoholism
• stops metabolism of ethyl alcohol by antagonizing
  effects of enzyme that converts acetaldehyde into
  acetic acid
• results in nausea, headache and stomach pain when
  alcohol is consumed
• but, abuser may just stop using pill to continue
  abuse
• best used as a supplement to abusers commitment
  to quit drinking
• 50 of Chinese Japanese culture has gene that
  slows metabolism of acetaldehyde

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Risk Factors for Alcohol Abuse

• Sons of alcoholics report low intoxication after
  drinking moderate amount
• feel less drunk, have less body sway and show
  less change in EEG
• more likely to abuse within 8 years of finding
• more likely to report more tension relief from
  drinking
• have smaller than normal amygdala, a potential
  predisposition to alcoholism
• Person high in sensation seeking more likely to
  be heavy drinker

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• Figure 15.7 Design for studies of predisposition
  to alcoholism. Sons of alcoholic fathers are
  compared to other young men of the same age and
  same current drinking habits. Any behavior in the
  first group is a predictor of later alcoholism.

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Major Depressive Disorder

• Sadness and helplessness for days and weeks at a
  time, low energy, feel worthless, contemplate
  suicide, little pleasure from sex or food
• Observed twice as often in women than men
• Affects about 5 of all adults at any one time
• Occurs between adolescence and old age
• Risk greater if relatives, especially female,
  have had long-lasting depression before age 30

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Major Depressive Disorder cont.

• Hormonal changes can trigger episode of
  depression in some women but they are not
  strongly correlated
• Interaction of heredity and environment and often
  triggered by traumatic events
• Stress can elevate cortisol which is debilitating
  and sets the stage for depression
• Many become depressed after damage to left
  hemisphere
• Borna virus predisposes people to psychiatric
  disorders, including depression

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Antidepressants

• Tricyclics prevent reuptake of serotonin or
  catecholamines (dopamine, epinephrine/nor-epinephr
  ine)
• side effects are dry mouth,drowsiness, difficulty
  urinating and heart irregularities
• MAO inhibitors block breakdown of serotonin and
  catecholamines
• for people who do not respond to tricyclics
• must avoid many foods that contain tyramine which
  combine with MAOIs to increase blood pressure

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Antidepressants cont.

• SSRIs, e.g., Prozac, Zoloft, block reuptake of
  serotonin
• mild side effects
• increases nervousness so not recommended for
  patients with both depression and anxiety
• Atypical antidepressants are a miscellaneous
  group that have differential affects on reuptake
  of serotonin, dopamine and norepinephrine, e.g.,
  Wellbutrin, venlaxafine
• mild side effects
• St. Johns wort is available without prescription
  but may or may not work
• decreases effectiveness of other medicines

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• Figure 15.11 Routes of action of antidepressants.
  Tricyclics block the reuptake of dopamine,
  norepinephrine, or serotonin. SSRIs specifically
  block the reuptake of serotonin. MAOIs block the
  enzyme MAO, which converts dopamine,
  norepinephrine, or serotonin into inactive
  chemicals. Atypical antidepressants have varying
  effects.

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Antidepressants cont.

• Conclusions
• drug has maximum effect in a few hours but most
  benefits may take days or weeks to alter behavior
  
• continued use may help restore hippocampus and
  cerebral cortex size by increasing neurotrophins
• mood depends on the effects of a combination of
  transmitters
• different depressed people have somewhat
  different transmitter abnormalities

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Therapies for Depression

• Psychotherapy produces metabolic changes similar
  to drugs and person is less likely to relapse
  after treatment
• 67 improve with drugs or psychotherapy or both,
  33 improve with no treatment
• Sleep deprivation works for certain patients
• depressed people enter REM sleep early, have
  trouble staying asleep and awaken early
• one night of total sleep deprivation or
  rescheduling sleep pattern relieves depression
• like drugs, reduces REM

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Therapies for Depression cont.

• ECT, abandoned in 1950s, relieves depression, but
  not known why it works
• less intense shock now and used for those who do
  not respond to drugs
• must be followed with drugs or ongoing ECT to
  prevent relapse
• works faster than drugs and muscle relaxants and
  anesthetics minimize discomfort
• no memory impairment if shock is given to right
  hemisphere only
• Intense magnetic field applied to scalp also
  effective