Developing and Testing an Online Intervention for Alcohol and Cannabis Misuse and Healthy Relationship Skills Among Young Adult Couples

The goal of this clinical trial is to develop and test a brief online intervention to reduce alcohol and cannabis misuse and improve healthy relationship skills among young adult couples. The main questions it aims to answer are: * Will the intervention be feasible and acceptable to young adult couples? * Will the intervention demonstrate initial efficacy in reducing risky substance use and increasing relationship functioning? Eligible couples will complete a virtual baseline session and be randomized to intervention condition (online intervention with 3-5 weeks of self-paced modules) or control condition (no intervention). Couples will complete two follow-up surveys (post-assessment - approximately 5 weeks after baseline, 3-month). Couples in the control condition will be offered the intervention after 3-month follow-up. Researchers will compare intervention and control groups to see if there there is a difference between the groups on substance misuse and relationship functioning at post-assessment and 3-month follow-up.