Objective: This study examined the association between baseline substance use and mental health, and non-partner violence trajectories among youth presenting to an urban emergency department who screened positive for drug use. Non-partner violence is physically violent victimization or aggression involving someone other than a dating partner.
Methods: Group-based trajectory modeling was used to identify longitudinal trajectories of non-partner violence in N = 599 youth (14-24 years old) at baseline, 6, 12, 18 and 24 month follow-ups. Multinomial logistic regression analyses were used to examine associations between baseline substance use and mental health conditions (i.e., anxiety, depression, and post-traumatic stress disorder [PTSD]), and non-partner violence trajectories.
Results: Six trajectory groups were identified for non-partner violence. Binge drinking and cannabis, illicit drug, nonmedical prescription stimulant, and polysubstance use in the 30 days leading up to their initial ED visit were associated with the likelihood of medium to high non-partner violence group membership during the two years following their ED visit. Post-traumatic stress disorder (PTSD) and depression/anxiety at baseline were also associated with greater risk of belonging to medium to high non-partner violence trajectory groups.
Conclusions: Our findings highlight distinct trajectories of violent behavior, with roughly 60 % of young adults belonging to one of the non-partner violence groups. Although general trajectory trends were of decreasing violent behavior, the constellation of baseline risk factors differentially predicted group membership. These findings indicate that violence does not operate in a vacuum; interventions to reduce violence should also address previous trauma, substance use, and mental health issues.
Keywords: Alcohol; Emergency department; Group-based trajectory modeling; Marijuana; Peer violence; Youth violence.
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