Source: Abnormal Psychology, University of Florida
Difficulty: Intermediate | Prerequisites: Part 1 of these study notes (Definitions and DSM Criteria). Familiarity with the concept of depressants and basic CNS pharmacology is helpful.
Depressants are one of the five substance classes covered in this chapter. They slow the central nervous system, and alcohol is the most widely used depressant worldwide. This section covers how alcohol affects the body at different doses, the three-stage withdrawal process (which can be fatal), and the epidemiology of alcohol misuse across gender, age, and cultural groups. If you understand alcohol as the prototypical depressant, the patterns for other depressants (benzodiazepines, barbiturates) will make more sense. The section closes with gambling disorder, which the DSM-5 groups with substance-related disorders because of shared behavioural and causal patterns.
Alcohol is a depressant that at low doses produces relaxation and euphoria but at higher doses causes depression-like symptoms, impaired coordination, blackouts, and potentially fatal respiratory paralysis. Withdrawal from heavy use follows three stages, the most severe being delirium tremens (DTs), which is fatal in about 10% of cases. Alcohol misuse is especially common among young adults and college students, with significant gender, age, and cultural variation in drinking patterns.
Depressants
Substances that slow the central nervous system. Alcohol is the most common example; others include benzodiazepines and barbiturates.
Disinhibitory effect
The reduction of normal behavioural restraints at low alcohol doses, producing feelings of confidence, relaxation, and mild euphoria. This is the effect most people find attractive about drinking.
Blackout (alcohol-induced amnesia)
A gap in memory for events that occurred while intoxicated, noticed only once the person sobers up. The person was conscious during the events but cannot recall them. This is a memory failure, not a loss of consciousness.
Blood alcohol concentration (BAC)
The percentage of alcohol in the bloodstream, used as a legal and clinical measure of intoxication. The legal limit in the U.S. is 0.08%. In simple terms, a higher BAC means more alcohol in your system and more severe impairment.
Respiratory paralysis
Cessation of breathing caused by extreme alcohol intoxication depressing the brainstem. Accounts for roughly one-third of alcohol-related deaths.
Tremulousness ("the shakes")
The first stage of alcohol withdrawal, characterised by trembling, weakness, and profuse sweating, typically appearing within a few hours of stopping or sharply reducing intake.
Delirium tremens (DTs)
The most dangerous stage (Stage 3) of alcohol withdrawal: auditory, visual, and tactile hallucinations, terrifying delusions, fever, irregular heart rate, agitation, and disorientation. Fatal in roughly 10% of cases.
Heavy drinking
Defined as 2+ drinks per day for men, 1+ for women.
Binge drinking
Defined as 5+ drinks in 2 hours for men, 4+ drinks in 2 hours for women.
Gambling disorder
An inability to resist the impulse to gamble, classified alongside substance-related disorders in DSM-5 because the behaviour patterns and underlying causes closely resemble those of substance use disorders.
Alcohol is the prototypical depressant. Its effects follow a dose-dependent curve.
Increased self-confidence, relaxation, mild euphoria, reduced inhibitions
This disinhibitory effect is what most people find attractive about drinking
People may feel "sexier" (mainly through reduced sexual inhibitions), but even low doses can impair sexual functioning
Induces symptoms of depression: fatigue, lethargy, decreased motivation, sleep disturbances, depressed mood, confusion
Slurred speech, unsteady gait, trouble paying attention, impaired memory
Slow, awkward physical reactions
Inappropriate behaviour, aggression, belligerence, mood swings
Stupor or coma
Blackouts: amnesia for events during intoxication, noticed only once sober
Absorption: food in the stomach slows absorption. An empty stomach means faster absorption via the small intestine.
BAC of 0.08 is the U.S. legal limit. Women typically reach this level with less alcohol than men because women are generally smaller and have lower body water content, producing higher alcohol concentrations per dose.
Impairment is invisible at dangerous levels. Deficits in attention, reaction time, and coordination are not always visible, even to trained observers. People often leave bars with a BAC well above the legal limit without appearing drunk.
Even a BAC of 0.02 (slightly buzzed) is linked to significantly increased automobile accident risk.
Respiratory paralysis accounts for about one-third of alcohol-related deaths, usually from a final large dose in someone already intoxicated.
Fatal interactions with other substances, including antidepressants.
600,000 deaths per year internationally from unintentional alcohol-related injuries (accidents, drownings, burns, poisonings).
Violence: more than half of all murderers and victims are believed to be intoxicated at the time. The same holds for people who attempt or complete suicide.
Withdrawal from heavy alcohol use progresses through three stages of increasing severity. Only about 11% of people with alcohol use disorder experience Stages 2 and 3.
Onset within a few hours of stopping or sharply reducing intake.
Tremulousness ("the shakes"), weakness, profuse perspiration
Anxiety ("the jitters"), headaches, nausea, abdominal cramps, retching and vomiting
Flushed, restless, easily startled but alert
EEG pattern may be mildly abnormal
May hear or see things (initially with eyes shut, then with eyes open)
People with moderate alcohol use disorder may only experience this stage, with symptoms disappearing within a few days
May begin as early as 12 hours after stopping, but more commonly on the second or third day
The most severe and dangerous stage.
Auditory, visual, and tactile hallucinations
Bizarre, terrifying delusions (e.g. monsters attacking)
Sleep deprivation, agitation, disorientation
Fever, profuse perspiration, irregular heart rate
Fatal in approximately 10% of cases. Death may occur from hyperthermia (extremely high body temperature) or collapse of the peripheral vascular system.
More common in people who drink large amounts in one sitting and who have a co-occurring medical illness
Heavy drinking: 2+ drinks daily for men, 1+ for women
Binge drinking: 5+ drinks in 2 hours for men, 4+ drinks in 2 hours for women
Both are associated with significant health problems
7% of U.S. adults are heavy drinkers
17-23% report binge drinking at least once a month
Binge drinking is especially common on college campuses: 35% of 18-22 year olds in college, versus 32% of the same age group not in college
75% in fraternities and sororities report binge drinking
Men are more likely to drink, drink heavily, or binge drink than women worldwide
Males are much more likely to develop alcohol use disorders across all ages
The gender gap is greater among people who follow traditional gender roles
The gap is even more pronounced in minority groups (Hispanic and Asian immigrants), where women are more likely to abstain entirely compared to European women
Alcohol use generally declines with age, for four reasons:
Older people become intoxicated faster and feel the negative effects more quickly
Greater maturity in decision-making about excess drinking
Older cohorts grew up under stronger cultural prohibitions against alcohol
Survivorship bias: people who used alcohol excessively when young may die before reaching old age
Although alcohol use is illegal under the age of 21 in the U.S.:
One-third of 8th graders and 70% of high schoolers have tried alcohol
22% of 12th graders report binge drinking in the past year
Age of onset is decreasing, and alcohol-related problems are increasing among youth
Earlier onset correlates with higher likelihood of developing a use disorder
Gambling disorder is classified alongside substance-related disorders in the DSM-5. It is defined as the inability to resist the impulse to gamble. The behavioural patterns and underlying causes closely parallel those of substance use disorders, including escalation, loss of control, and continued engagement despite mounting negative consequences.
The dose-dependent effects of alcohol explain why someone can seem "fine" at a party and still be dangerously impaired behind the wheel: deficits in attention, reaction time, and coordination are often invisible even to trained eyes. This is why breathalyser tests exist rather than relying on observation.
The three-stage withdrawal model is the reason hospitals taper alcohol-dependent patients off gradually rather than stopping abruptly. Cold-turkey cessation in a heavily dependent person can trigger seizures or DTs, both of which can be fatal.
The gender and body-composition data (women reaching higher BAC at the same dose) is the basis for the different thresholds in the definitions of heavy and binge drinking.
"A blackout means the person passed out." A blackout is a memory gap, not a loss of consciousness. The person was awake and functioning during the events they cannot recall.
"If someone doesn't look drunk, they're safe to drive." Impairment in attention, reaction time, and coordination is often invisible to observers. People frequently leave social settings with a BAC well above the legal limit while appearing sober.
"Alcohol withdrawal is just unpleasant, not dangerous." Withdrawal can be life-threatening. Delirium tremens is fatal in roughly 10% of cases, and convulsive seizures can also cause serious injury or death.
"Men and women are affected the same way by the same amount of alcohol." Women generally reach higher BAC levels from the same dose due to lower body water content and smaller body size. This is why the clinical thresholds for heavy and binge drinking are lower for women.
Know the three stages of alcohol withdrawal in order (tremulousness, convulsive seizures, delirium tremens) and the key features of each.
DTs are fatal in about 10% of cases. Know the two causes of death: hyperthermia and collapse of the peripheral vascular system.
Only 11% of people with alcohol use disorder progress to Stages 2-3. This statistic is commonly tested.
Know the definitions and thresholds for heavy drinking and binge drinking, including the gender-specific cutoffs.
The gender and age epidemiology of alcohol misuse is exam-relevant: men drink more across all ages, the gender gap varies by culture, and earlier onset predicts worse outcomes.
Gambling disorder's placement alongside substance-related disorders (shared patterns and causes) is a likely short-answer or multiple-choice point.
True or False: A blackout means the person lost consciousness. (False. A blackout is amnesia for events during intoxication; the person was conscious.)
Fill in the blank: The three stages of alcohol withdrawal, in order, are tremulousness, ______, and delirium tremens. (Convulsive seizures.)
True or False: Delirium tremens occurs in most people who stop heavy drinking. (False. Only about 11% of people with alcohol use disorder experience Stages 2-3.)
Fill in the blank: Binge drinking is defined as ______ drinks in 2 hours for men and ______ drinks in 2 hours for women. (5+; 4+.)
True or False: Women reach higher BAC levels than men from the same dose of alcohol. (True, due to lower body water content and generally smaller body size.)
Q: Describe the dose-dependent effects of alcohol, from low doses through extreme intoxication.
A: At low doses, alcohol produces relaxation, mild euphoria, increased confidence, and reduced inhibitions (the disinhibitory effect). As doses increase, it induces depression-like symptoms: fatigue, lethargy, impaired coordination, slurred speech, memory problems, and mood swings. At extreme levels, the person may fall into stupor or coma, and respiratory paralysis can cause death.
Q: Name the three stages of alcohol withdrawal and identify which stage is most dangerous.
A: Stage 1 is tremulousness (the shakes, anxiety, nausea, sweating). Stage 2 is convulsive seizures (onset typically 12+ hours after cessation). Stage 3 is delirium tremens (DTs), involving hallucinations, terrifying delusions, fever, and irregular heart rate. Stage 3 is the most dangerous, with a fatality rate of approximately 10%.
Q: Why do the definitions of heavy drinking and binge drinking use different thresholds for men and women?
A: Women generally have lower body water content and smaller body size than men, so the same dose of alcohol produces a higher blood alcohol concentration. The lower thresholds for women reflect this physiological difference.
Q: A 20-year-old college student in a fraternity binge drinks most weekends. Based on the lecture data, how common is this pattern?
A: Very common. 75% of fraternity and sorority members report binge drinking, and 35% of 18-22 year olds on college campuses binge drink. Earlier onset of drinking also correlates with a higher likelihood of developing a substance use disorder.
Q: Why is gambling disorder grouped with substance-related disorders in the DSM-5 rather than with impulse-control disorders?
A: Because the behavioural patterns and underlying causes of gambling disorder closely resemble those of substance use disorders, including escalation, loss of control, and continued engagement despite negative consequences.
Alcohol's depressant effects connect directly to the neuroscience material from earlier in the course: it works by enhancing GABA activity and inhibiting glutamate in the CNS. The comorbidity between alcohol use disorders and mood disorders (Chapter 6) is high, and understanding withdrawal symptoms helps explain why some patients present with anxiety or depression that is substance-induced rather than primary. The epidemiology data here also links to broader discussions of risk factors and developmental psychopathology, particularly the finding that earlier onset predicts worse outcomes.
Depressants, alcohol, alcohol intoxication, alcohol withdrawal, delirium tremens, DTs, tremulousness, convulsive seizures, blackout, blood alcohol concentration, BAC, respiratory paralysis, disinhibitory effect, heavy drinking, binge drinking, alcohol misuse, gender differences in alcohol use, underage drinking, college binge drinking, fraternity drinking, gambling disorder, behavioural addiction, abnormal psychology, University of Florida, Chapter 14