Further, while our study cohort did not include subjects with any comorbid psychiatric disorders or a current or past history of other substance dependence or abuse, our marijuana smoking subjects did report more frequent use of alcohol than the non-marijuana smoking control subjects. Regression analyses of the association between total number of drinks over the last 30 days and brain activation within the marijuana smokers, however, suggest that while there is some detectable cingulate gyrus activation associated with alcohol use in the last month for the marijuana smokers, this is in different regions of the cingulate cortex than those reported to be associated with marijuana use alone. Therefore, it appears that the relationship between marijuana use and BOLD activation during both masked affective tasks is different from the one detected for alcohol use and BOLD activity. Future studies will need to address the relationship between alcohol and marijuana use in order to determine the specific effects of each substance on brain activation patterns.
