Introduction This paper examines associations between high-risk gun carrying and substance use in emerging adults (ages 18–22). The coexistence of these high-risk behaviours in a general population of emerging adults can have disastrous consequences.

Methods Dating it Safe is an ongoing longitudinal (2010–2016) survey of emerging adults recruited from seven high schools in five south-east Texas-area school districts (current sample n=684). Multiple logistic regression modelling was used to examine the association between past-year use of legal and illegal substances and past-year firearm carrying for a reason other than sport or hunting.

Results 6% of emerging adults carried firearms in the past year, with most (68%) carrying for protection. Use of cocaine, hallucinogens, methamphetamine, ecstasy and prescription medications in the past year, as well as episodic heavy drinking in the past month, was associated with increased risk of carrying a firearm (p<0.05 for all). After controlling for covariates, hallucinogens (OR 2.81, 95% CI 1.00 to 7.81), ecstasy (OR 3.66, 95% CI 1.32 to 10.14) and prescription medications (OR 2.85, 95% CI 1.22 to 6.68) remained associated with firearm carrying. Episodic heavy drinking was associated with firearm carrying, but only for those who had five or more episodes/month (OR 3.61, 95% CI 1.51 to 8.66).

Conclusions In this community-based sample of emerging adults, firearm carrying, mostly for protection, was associated with a variety of past-year substance use behaviours. These findings extend previous research and suggest directions for further exploration of the clustering of high-risk behaviours in emerging adults.