The influence of alcohol and marihuana on motor and mental performance

Abstract

Twelve healthy male volunteers smoked marihuana cigarettes calibrated to deliver 0, 2.5, or 5 mg. of delta‐9‐tetrahydrocannabinol (THC) either alone or in combination with either a plain fruit‐flavored beverage or the same beverage containing 15 ml. of alcohol per 50 pounds of body weight. Each subject received all 6 possible combinations in a double‐blind randomized block experiment. The parameters measured were four pursuit meter tests (motor performance), nine delayed auditory feedback tests (mental performance), pulse rate, conjunctival injection, and subjective effects (Cornell Medical Index). It was found that the high dose of THC produced Significant impairment in performance of both mental and motor tasks and that alcohol induced an additional effect. There was little difference between the response to 2.5 and 5.0 mg. of THC on these parameters. Conjunctival injection, ptllse rate, and subjective effects were dose dependent and alcohol was additive.