Cross-fading motives for simultaneous alcohol and marijuana use: Associations with young adults' use and consequences across days

Background: Many young adults engage in simultaneous alcohol and marijuana (SAM) use so that their effects overlap. Little is known about motivations for dual substance use and associations with use and consequences. This study examined daily-level associations between cross-fading motives and levels of alcohol and marijuana use and consequences. Methods: Young adults who reported SAM use in the month prior were surveyed in two 14-day bursts. Data included 1049 SAM use days from 281 young adults (age 18-25; M age = 21.80, SD = 2.16; 50 % women). Multilevel models assessed between- and within-person effects of cross-fading motives (i.e., to enhance the effects of marijuana and/or alcohol use by using them simultaneously) on alcohol and marijuana use and consequences, after adjusting for general enhancement, social, coping, and conformity motives and the amount of alcohol and marijuana used that day. Results: On 76 % of SAM use days, participants endorsed cross-fading motives (i.e., to enhance the effect of alcohol or marijuana or to get drunk and high at the same time). Having stronger cross-fading motives was associated with greater alcohol use, perceived intoxication, and positive alcohol consequences at the between- and within-person levels. In addition, between-person, individuals who reported stronger cross-fading motives on average reported more negative alcohol consequences and positive marijuana consequences on average. Cross-fading motives on a given day were not associated with marijuana use or marijuana consequences that day. Conclusions: Cross-fading motives were common and varied from day to day. Understanding the motivational context for dual substance use may support future interventions for cross-fading.