The National Commission on Marihuana and Drug Abuse

Marihuana - A Signal of Misunderstanding.

Chapter II

marihuana use and its effects

Mental Function

Marihuana, like other psychoactive substances, predominantly affects mental processes and responses (cognitive tasks) and thus the motor responses directed by mental processes (psychomotor tasks). Generally, the degree of impairment of cognitive and psychomotor performance is dose-related, with minimal effect at low doses. The impairment varies during the period of intoxication, with the maximal effect at the peak intoxication. Performance of simple or familiar tasks is at most minimally impaired, while poor performance is demonstrated on complex, unfamiliar tasks. Experienced marihuana users commonly demonstrate significantly less decrement in performance than drug-naive, individuals.

The greater his past marihuana experience, the better the intoxicated individual is able to compensate for drug effect on ordinary performance at usual doses. Furthermore, marked individual variation in performance is noted when all else is held constant. The effect of marihuana on cognitive and psychomotor performance is therefore highly individualized and not easily predictable. Effects on emotional reactions and on volition are equally variable and are difficult to measure under laboratory conditions, but can be significant.