Behavioral Effects

Alcohol has a wide range of behavioral effects and for centuries has been widely regarded as both a sedative and stimulant. To quote Shakespeare from Macbeth, Act II, Scene III:

Porter. Faith, sir, we were carousing till the second cock; and drink, sir, is a great provoker of three things.

Macduff. What three things does drink especially provoke?

Porter. Merry, sir, nose-painting, sleep, and urine. Lechery, sir, it provokes, and unprovokes; it provokes the desire, but it takes away the performance; therefore, much drink may be said to be an equivocator with lechery; it makes him, and it mars him; it sets him on, and it takes him off; it persuades him, and disheartens him; makes him stand to, and not stand to; in conclusion, equivocates him in a sleep, and, giving him the lie, leaves him.

Alcohol, a sedative hypnotic, produces dose-dependent behavioral effects in humans, including sedation (decreases in activity) and hypnosis (sleep induction). At low doses (blood alcohol levels of 0.01–0.05 g%), alcohol produces personality changes, including increased sociability, increased talkativeness, and a more expansive personality (Figure 6.2, Table 6.3, Box 6.3). Such blood alcohol levels are associated with mild euphoria, improved mood, good feelings, increased confidence, and increased assertiveness. Some release of inhibitions also occurs, with tension reduction and increased responsiveness (and sometimes combativeness) in conflict situations. As the dose increases from 0.08 to 0.10 g%, mood swings become more pronounced, with euphoria, emotional outbursts, and a greater release of inhibitions. Blood alcohol levels of 0.08 g% produce distinct impairment in judgment, and motor dysfunction is apparent. Blood alcohol levels of 0.15 to 0.20 g% are associated with marked ataxia, major motor impairment, staggering, slurred speech, muscular incoordination, and impairment in reaction time. Sensory responses are also impaired, including a loss of vestibular sense and decreased pain sensation. Such blood levels also dull concentration and insight, impair discrimination and memory, significantly impair judgment, cause greater emotional instability, and profoundly release inhibitions. At this level, “blackouts” can occur, in which a person will have no later memory of the events that transpired while the person was intoxicated. At blood levels of 0.30 g%, people become stuporous but are still conscious. This is an anesthetic level of intoxication, with marked decreases in responsivity to environmental stimuli, severely impaired motor function, and rapid and dramatic changes in mood. Vomiting can occur at this level. The lethal dose in 50% of individuals (referred to as the LD50) is approximately 0.50 g% in nondependent individuals (alcohol-dependent individuals may have a significantly higher LD50; see section on tolerance below; Box 6.4).

Figure 6.2 Progression of subjective and physiological changes that correspond to increased blood alcohol levels.

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