Visual search in long-term cannabis users with early age of onset

The present research tested the hypothesis that there is a specific deficit in visual scanning in chronic users of cannabis with early onset of their drug consumption (age 14 to 16). 17 users and 20 control participants were asked to search for targets on a 5 x 5 stimulus array while their eye movements were monitored. Cannabis users showed less effective search behavior, including longer response times and more fixations at about the same error level. Search patterns were more conservative and included more frequent reinspections of previously fixated areas. In sum, the results point to two loci of adverse effects: an impairment in visual short-term memory, and less effective visual processing at a more strategic, top down controlled level.