Substance use to cope with trauma: the interactive effect of insomnia and neighborhood socioeconomic status.

STUDY OBJECTIVES: Emerging literature suggests insomnia predicts post-trauma substance use. Socioeconomic context may exacerbate this relation, such that individuals with insomnia living in more disadvantaged areas may face elevated risk of substance use after trauma. The present study is the first to test whether insomnia predicts later substance use to cope after trauma, and whether this effect is stronger for individuals from more disadvantaged areas. MATERIALS AND METHODS: Patients recruited from an urban Level I trauma center following traumatic injury (N = 88, M age = 39.5 ± 14.3) were evaluated for clinically significant insomnia (Insomnia Severity Index; ISI ≥ 15) and frequency of substance use to cope with trauma (Brief-COPE) during hospitalization (Time 1 [T1]), one month post-trauma (Time 2 [T2]), and two months post-trauma (Time 3 [T3]). Participants were classified as belonging to "more" or "less" disadvantaged areas based on their residential ZIP codes using the Social Vulnerability Index (SVI). RESULTS: The interaction between T1 insomnia and SES significantly predicted the frequency of substance use to cope one-month post-trauma (p = .01, η2 p  = .11). Surprisingly, participants with insomnia living in less disadvantaged areas reported greater substance use to cope than those in more disadvantaged areas. A similar interaction emerged between T2 insomnia and SES on substance use to cope two months post-trauma (p = .04, η2 p  = .09). No such differences were observed among participants without insomnia. CONCLUSIONS: Living in less disadvantaged areas exacerbated the prospective effect of insomnia on risk for substance use to cope after trauma. Trauma patients with insomnia may benefit from sleep-focused interventions that consider alternative coping strategies to substance use.