Past year high-intensity drinking moderates the association between simultaneous alcohol and marijuana use and blackout frequency among college students.

The role of simultaneous alcohol and marijuana (SAM) use in the experience of blackouts among college students is unclear. To clarify discrepancies, the current study evaluated whether the association between SAM user status and blackouts was moderated by high-intensity drinking (HID). College students (N = 1,224; 63.7% female) reported on their past year experiences of blackout, marijuana use, SAM use, and HID (i.e., drinking at least twice the binge threshold). SAM users had more past year blackouts than non-SAM users, but this effect was only significant among SAM users who had engaged in HID in the past year (nonbinge: = 0.50,  = 0.49; binge: = 0.23,  = 0.63; HID: = 4.52,  = 0.03). Effects of SAM user status on the experience of alcohol-related blackouts may be limited to individuals who engage in HID.