Schaffer Library of Drug Policy |
Marihuana: A Signal of Misunderstanding
Acute Effects of Marijuana (Delta 9 THC) - Effects on Mentation and Psychomotor Performance
US National Commission on Marihuana and Drug Abuse
The Report of the National Commission on Marihuana and Drug Abuse Acute Effects of Marihuana(Delta 9 THC)
EFFECTS ON MENTATION AND PSYCHOMOTOR PERFORMANCE Characteristically, intoxication with psychoactive materials effect psychomotor and mental functions. It is apparent from the subjective assertions of users and a wide range of experimental studies that marihuana is no exception (Clark and Nakashima , 1968; Clark et al., 1970; Dornbush and Freedman, 1971; Hollister and Gillespie, 1970; Manno et al., 1970; Mayor's Committee, 1944; McGlothlin et al., 1971; Melges et al., 1970; Meyer et al., 1971; Weil and Zinberg, 1969; Weil et al., 1968; Volavka et al., 1971; Galanter et al., 1972; Kiplinger et al., 1971; Mendelson et al., 1972; Dornbush et al., 1971). Psychomotor tasks which have been tested include tapping speed, handwriting and
free-hand writing and free handdrawing, simple and complex reaction time, pursuit rotor
and tracking tasks and continuous performance tests. Cognitive tasks frequently tested are
simple arithmetic problems, serial addition or subtraction, fine judgment tasks,
'digit-symbol substitution test, digit-code memory, reading comprehension, speech or
verbal out-put, forward and backward digit spans, goal directed complex serial
subtractions and additions to reach a set end sum, and short-term or immediate memory
functions. In general, Kiplinger et al. (1971) have clearly demonstrated that the degree of impairment is dose related and varies in degree during the period of intoxication exerting its maximal effect at the peak intoxication. Naive subjects commonly demonstrate greater decrement in performance than experienced
users but report less subjective effect (Weil et al., 1968). Experienced users appear to
better compensate to the effect of the drug especially for ordinary performance at lower
doses (Clark and Nakashima, 1968; Clark et al., 1970; Crancer et al., 1969; Jones and
Stone, 1970; Meyer et al., 1971; Weil and Zinberg, 1969; Jones, 1971; Mendelson et al.,
1972). Performance of simple or familiar tasks (i.e. simple reaction time) during
intoxication is minimally effected. However, on unfamiliar or complex tasks (i.e., complex
reaction time), performance decrements occur (Weil and Zinberg, 1969; Dornbush et al.,
1971; Moskowitz et al., 1970). Performance decrements are further enhanced when verbal tasks are performed during delayed auditory feedback (Kiplinger et al., 1971). Also marked individual differences in performance are noted between similar subjects. (Clark and Nakashima, 1968; Clark et al., 1970; Manno et al., 1970; Kiplinger et al., 1971). A cyclical waxing and waning of the intensity of the intoxication and concomitant performance occurs periodically (Clark et al., 1970; Melges et al., 1970). Finally, when subjects concentrate on the task being performed at "normal social
high," objective evidence of intoxication is not apparent and the individual may
perform better than when drug free (Rodin and Domino, 1970; Mendelson et al., 1972). Obviously, these observations raise practical doubts regarding the intoxicated
individuals' ability to function at jobs requiring memory, concentration, and organization
of thinking. |