ACUTE AND RESIDUAL EFFECTS OF ALCOHOL AND MARIJUANA, ALONE AND IN COMBINATION, ON MOOD AND PERFORMANCE

The duration of behavioral impairment after marijuana smoking remains a matter of some debate. Alcohol and marijuana are frequently used tog ether, but there has been little study of the effects of this drug com bination on mood and behavior the day after use. The present study was designed to address these issues. Fourteen male and female subjects w ere each studied under four conditions: alcohol alone, marijuana alone , alcohol and marijuana in combination, and no active treatment. Mood and performance assessments were made during acute intoxication and tw ice the following day (morning and mid-afternoon). Acutely, each drug alone produced moderate levels of subjective intoxication and some deg ree of behavioral impairment. The drug combination produced the greate st level of impairment on most tasks and ''strong'' overall subjective ratings. There were few significant interactions between the two drug s, indicating that their effects tended to be additive. Only weak evid ence was obtained for subjective or behavioral effects the day after a ctive drug treatments, although consistent time-of-day effects (mornin g versus afternoon) were observed on several subjective and behavioral measures. In sum, this study provided little evidence that moderate d oses of alcohol and marijuana, consumed either alone or in combination , produce behavioral or subjective impairment the following day.