USMLE Step 1 Web Prep — Alcohol and Alcoholism
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Substance Abuse
Alcohol and Alcoholism
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Physiology of Substance Abuse
 The basic addiction pathway in the brain is a dopamine pathway
 Activation of this pathway accounts for the “positive reinforcement” feeling
Medial forebrain bundle (MFB)

Nucleus accumbens (NAC)

Ventral tegmental area (VTA)
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Physiology of Substance Abuse
  • Pathway helps to make behavior adaptive and goal directed.
  • Ingestion of chemicals gives the positive reinforcement without the linkage to environment
  • Makes behavior less and less environmentally responsive over time.
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Physiology of Substance Abuse
  • This addiction pathway is activated by all substances that produce psychological dependence
  • Serotonin (5-HT) also plays a role in the addiction process due to its regulation of impulse control
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Alcohol and Alcoholism
  • Cost the US around $100 billion a year
  • Most costly health problem
  • Tobacco accounts for more loss of life
  • The best way to reduce long-term mortality is to eliminate smoking
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Epidemiological Facts
  • Alcohol: most abused drug for all ages
  • 10% of all adults are problem drinkers
  • Male to female ratio is 4 to 3
  • Since 1980, per capita consumption of alcohol has declined
  • The proportion of heavy drinkers younger than 20 has increased
  • Binge drinking is becoming more common
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Alcohol and SES
  • Alcoholism rates are higher for the low SES groups
  • Low SES alcoholics recover sooner and at higher rates (if they survive)
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Accidents
  • Alcohol use has been implicated in 15% of all auto accidents
  • Alcohol use implicated in 50% of all:
  • Auto accidents not involving a pedestrian
  • Auto accident deaths
  • Homicides (killer or victim)
  • Hospital admissions
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Fetal Alcohol Syndrome
  • The leading known cause of mental retardation (Down’s syndrome is second)
  • Characterized by:
  • developmental and mental retardation
  • craniofacial abnormalities
  • limb dislocation
  • Consumption of large quantities of alcohol needed to produce FAS
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Evidence for Genetic Contribution
  • Increasing evidence for genetic contribution
  • Concordance rates: MZ > DZ
  • Marked ethnic-group differences
  • Capacity to tolerate alcohol is the key (enzyme induction, lack of tyrosine kinase)
  • If biologic father was an alcoholic, the incidence of alcoholism in males adopted into nonalcoholic families is equal