Longitudinal Effects of Military Separation and Mental Health Symptomatology on Substance Use Among a Cohort of Reservists

Objective: The relationship between mental health and substance use among military populations is well established, and evidence suggests that these risks may be greater for those who have left the military. However, it is less clear what independent effects leaving the military may have on substance use behaviors. This study examined the longitudinal relationship between leaving the military and substance use outcomes (hazardous drinking, frequent heavy drinking, nonmedical use of prescription drugs, illicit drug use) in a cohort of Reserve and National Guard (R/NG) soldiers. Further, we examined whether mental health symptoms moderate the relationship between leaving the military and substance use. Method: Analyses used data (N = 485 soldiers) from the first four annual waves of Operation: SAFETY, an ongoing prospective cohort study of U.S. Army R/NG soldiers and their spouses. We used generalized estimating equations (GEEs) to examine the relationships between military status (former vs. current soldier) and substance use outcomes over 4 years. Last, we examined interactions between military status and mental health indicators (anxiety, anger, depression, and posttraumatic stress disorder) on substance use over time. Results: After we controlled for sex, age, race, years of military service, sleep problems, bodily pain, and substance use norms, being a former soldier, compared with being a current soldier, was associated with greater odds of current illicit drug use (adjusted odds ratio = 2.86, 95% CI [1.47, 5.57]; p < .01). Mental health symptomatology did not moderate the relationship between leaving the military and current drug use. Conclusions: Leaving the military in and of itself may result in increased drug use for some individuals, regardless of mental health symptomatology. (J. Stud. Alcohol Drugs, 85, 528–536, 2024).