Among infrequent (nondaily) users, marijuana causes impairment in the areas of attention and concentration, impulse control, planning, decision making, and working memory 0–6 h after use (46, 74). Marijuana use results in slower response time in tasks of simple reaction time, visuospatial selective attention, sustained attention, divided attention, and short-term memory, as well as impairment on a task of motor control (75). In chronic, daily users of cannabis, acute abstinence results in greater cognitive impairment than acute use. In fact, marijuana may normalize the cognitive dysfunction seen with cannabis withdrawal; however, this likely represents a lower level of cognitive function compared to that prior to onset of use (74). No significant differences were observed for critical-tracking or divided-attention task performance in a cohort of heavy, chronic cannabis smokers (76).
