Differential association between chronic cannabis use and brain function deficits.
To summarize, 12 objective tests that generated 16 test variables were administered to 850 male regular cannabis users and 839 nonusers. The tests were designed to assess various modalities, including speed of psychomotor performance, distance estimation, time estimation, immediate memory, and visuomotor coordination. Most of the test variables differentiated significantly between consumers and controls. At the same time, a significant second-order interaction emerged in most cases. This interaction meant that, under certain conditions that relate to the two dimensions "literacy-illiteracy" and/or "urbanism-ruralism," the superiority of controls over cannabis users became impressive, whereas under other conditions it almost disappeared. To account for this complex pattern of results, a working hypothesis was presented to the effect that "other conditions being equal, the lower the nondrug  level of proficiency on tests of cognitive and psychomotor performance the smaller the size of function deficit associated with drug usage." For an empirical examination of the hypothesis, six predictions were formulated. Three predictions defined specific relationships between level of performance, on one hand, and each of three organismic variables, on the other: literacy, urbanism, and age. The remaining predictions delineated relationships to be expected between size of function deficit and the three organismic variables. All our predictions were confirmed, showing less function impairment to be contingent with cannabis usage among the illiterates, rurals, and older subjects. Level of cortical arousal was suggested as the central process associated with the three organismic variables. Because the version of our working hypothesis was formulated with reference to chronic material, the possibility of a transposition of the paradign to research on the acute effects of the drug was discussed. The suggestion was made that our working hypothesis, in either version, is capable of establishing genuine integration between reports that present conflicting results on possible function deficits contingent with cannabis consumption.
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001921:Brain / Q000187:drug effects*; D002188:Cannabis; D004215:Distance Perception / Q000187:drug effects; D004522:Educational Status; D004534:Egypt; D005556:Form Perception / Q000187:drug effects; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000187:drug effects; D008606:Mental Processes / Q000187:drug effects*; D011939:Mental Recall / Q000187:drug effects; D008875:Middle Aged; D009048:Motor Skills / Q000187:drug effects; D011930:Reaction Time / Q000187:drug effects; D012424:Rural Population; D019966:Substance-Related Disorders / Q000503:physiopathology*; D013998:Time Perception / Q000187:drug effects; D014145:Trail Making Test; D014505:Urban Population