Investigators from the University of Colorado, Boulder and the Oregon Health & Science University evaluated neuroimaging data among adults (ages 18 to 55) and adolescents (ages 14 to 18). Authors identified an association between alcohol use and negative changes in brain structure, but identified no such association with cannabis.
"Alcohol use severity is associated with widespread lower gray matter volume and white matter integrity in adults, and with lower gray matter volume in adolescents," they concluded. By contrast, "No associations were observed between structural measures and past 30-day cannabis use in adults or adolescents."
Researchers acknowledged that their findings were similar to those of prior studies "suggesting that regionally specific differences between cannabis users and non-users are often inconsistent across studies and that some of the observed associations may actually be related to comorbid alcohol use."