The effect of marihuana on tracking task perfomance

A 5-min paced contour tracking task was performed before and after receiving brownies containing either placebo or marihuana calibrated to a ⁹-tetrahydrocannabinol content of 20 mg. The error patterns of 19 young male subjects who received placebo and 18 who received marihuana were compared. After marihuana there was an increase in total errors as measured by the standard deviation (P<0.01) and the mean deviation (P<0.02) error scores. Although marihuana is reputed to create a fluctuating effect, under the conditions of this experiment the variability of error scores between successive 15-second time periods in the marihuana group was not significantly greater than in the placebo group. In addition the marihuana deficit did not show significant time trends during the task.This research was supported by NIMH Grant MH 03030 and Veterans Administration Project 5019-02.The authors thank Dr. Helena Kraemer for statistical consultation.