Simultaneous use of alcohol and marijuana is riskier than using either substance alone, because their effects can interact and cause excessive depression of the central nervous system. This can result in more negative consequences such as driving under the influence, accidents, cognitive impairment, and symptoms of substance use disorders, as well as alterations in mood and well-being.
There has been little research on simultaneous alcohol and marijuana use among college students following legal changes regarding medical and recreational marijuana use in some states. A new study has evaluated patterns of simultaneous substance use among students in three state universities with different state laws on recreational marijuana use.
The study involved 1400 students who had used both alcohol and marijuana (alone and/or together) in the past year, and who completed an online survey assessing their own substance use and negative consequences, perceptions of simultaneous alcohol and marijuana use among peers and close friends, and ease of access to marijuana.
Overall, three-fourths of participants reported having used alcohol and marijuana simultaneously in the past year, on average twice per month. After controlling for overall frequency of alcohol and marijuana use, students in a state with decriminalized marijuana use reported greater simultaneous alcohol and marijuana use than those in a state with legalized use – despite more students at the latter school (52% vs 47%) reporting very easy access to marijuana. Less surprisingly, students in a state with criminalized marijuana use reported the lowest frequency of simultaneous alcohol and marijuana use.
Previous research has shown that students' perceptions of substance use among their peers (which may differ from their peers' actual use) have a strong influence on their own behaviors. Consistent with this, the new study found that students who perceived high rates of simultaneous alcohol and marijuana use among their peers (and particularly among their close friends) were more likely to engage in frequent simultaneous alcohol and marijuana use themselves ─and were also more likely to experience negative consequences.
The findings suggest that the 'normative environment' of a campus may be a more important infuence on simultaneous alcohol and substance use than the state's legal environment. However, other factors, such as the racial mix of students or existing campus prevention/enforcement strategies, may also partly account for the differing rates of simultaneous substance use across schools.
Overall, the study indicates that a large majority of students who use alcohol and marijuana may be at risk for serious harm resulting from their simultaneous use Prevention and intervention programs that seek to reduce simultaneous substance use – perhaps by addressing students' perceptions of peer use compared with actual use ─would be of benefit.