Interestingly, in our preliminary comparison of prefrontal cortex volumes of 16 marijuana-using and 16 control adolescents, few differences were observed. However, among females, marijuana users had a 4% larger posterior and prefrontal cortex volume (p=.06) than non-users, on average. This was associated with poorer verbal memory, suggesting potentially interrupted synaptic pruning in female users. Marijuana-using adolescents showed larger global gray matter volumes than controls, with increased marijuana use predicting increased volume (β=.61, p<.01) and poorer verbal and attention performance 35. These findings also suggest that marijuana use during adolescence may disrupt gray matter pruning processes.
