Experimental studies indicate that acute intoxication with marijuana affects a number of cognitive and motor skills that are relevant to driving, including reaction time, attention, signal detection, information processing speed, spatial working memory, verbal learning and recall, procedural memory, tracking accuracy, time and distance estimation, set shifting, motor coordination, and danger perception (46). Results from driving simulator studies suggest that the effects of marijuana on driving may be dose dependent, with minimal to no impairment at low doses (67, 68) and progressive impairment with increasing dose (64). Also, the effects of marijuana may be more pronounced as the complexity of tasks increases (69). Notably, heavy users may exhibit minimal functional impairment in selected driving tasks (64, 70), presumably due to tolerance.
