Expectancy and tolerance: a study of acute alcohol intoxication using the balanced placebo design.

Interactive effects of expectancy and alcohol dose on CNS functioning were examined in subjects differing in degree of dependence on alcohol, using the balanced placebo design. Male subjects (N = 30), 10 severely-, 10 moderately- and 10 nondependent on alcohol, were tested with the Klove-Matthews Motor Steadiness Battery before and after drinking. The administered alcohol dose yielded .07 mg/dl mean blood alcohol level. Expectations about alcohol resulted in impaired sensorimotor coordination in severely dependent alcoholics, as compared to expectations of soft drinks. Moderately dependent subjects showed an opposite response pattern. Such expectancy factors may counteract neuropharmacological tolerance effects, neutralizing real tolerance effects on moderate doses of alcohol for severely dependent alcoholics. High tolerance also makes larger quantities necessary, leading to increased consumption to obtain the same effect.