Co-Using Alcohol and Cannabis Leads to More Drinks and Worse Outcomes | Research

The takeaway

On days when young adults used both alcohol and cannabis together, they drank more than on alcohol-only days, and it was this higher drinking — not co-use itself — that drove more negative consequences.

Young adults who use both substances, harm reduction counselors, college health professionals, and addiction researchers.

What the researchers found

Number of alcoholic drinks significantly mediated the association between co-use and consequences: co-use days involved more drinking, which drove higher negative consequences and lower positive consequences — suggesting alcohol quantity, not cannabis addition, is the key driver.

Why it matters

This clarifies a long-standing question: co-use days are riskier not because cannabis inherently worsens outcomes, but because people drink more on those days — pointing to drink reduction as the primary harm-reduction target.

The numbers in context

N=115 young adults; 28-day daily diary; significant mediation for both positive and negative consequences; more drinks on co-use days vs. alcohol-only days; drink quantity mediated the co-use → negative consequences pathway

How the study worked

28-day field-based study using morning reports from 115 young adults (ages 18-25) with frequent alcohol and cannabis use, analyzing day-level multilevel mediation models of co-use, drink quantity, and consequences.

What this study cannot tell us

Self-report morning recall; 28-day window may not capture all patterns; sample of frequent users may not generalize; mediation design limits causal claims; did not distinguish concurrent vs. simultaneous use.

How to read the evidence

Well-designed daily diary study with appropriate multilevel mediation analysis, providing granular within-person data despite reliance on self-report.

When this study was published

Published 2026; reflects current young adult substance use patterns.

The bigger picture

For harm reduction among young adults who co-use, the message is simple: focus on drink counting. Cannabis co-use correlates with heavier drinking days, making alcohol moderation the most actionable intervention.

Questions still open

Why do people drink more on co-use days? Would cannabis availability as a substitute reduce drinking? Does the order of substance use (cannabis first vs. alcohol first) affect consumption patterns?

Common questions

Is mixing alcohol and cannabis more dangerous?

This study found that co-use days led to more negative outcomes, but primarily because people drank more alcohol on those days — suggesting that managing alcohol quantity is key to reducing co-use risks.

Does cannabis make you drink more?

On days when young adults used both substances, they consumed more alcoholic drinks than on alcohol-only days. Whether cannabis directly increases drinking or whether heavier drinking nights simply tend to include cannabis use isn't fully clear.

Read the original research

Alcohol quantity mediates the association between daily alcohol and cannabis co-use and alcohol consequences.

Drug and alcohol dependence, 279, 113043

View on PubMed ↗Publisher’s paper ↗

Citation

Gunn, Rachel L; Sokolovsky, Alexander W; Howe, Lindy K; Barnett, Nancy P; Jackson, Kristina M; Lipperman-Kreda, Sharon; Miranda, Robert; Trull, Timothy; Metrik, Jane. (2026). Alcohol quantity mediates the association between daily alcohol and cannabis co-use and alcohol consequences.. Drug and alcohol dependence, 279, 113043. https://doi.org/10.1016/j.drugalcdep.2026.113043