Posttraumatic stress disorder (PTSD) and substance use disorder (SUD) commonly cooccur following trauma, and their co-occurrence is associated with substantial costs; however, our understanding of the timing and sequencing of these posttrauma mental health conditions is limited. This study examined the trajectories of PTSD symptom severity and substance use among individuals recently exposed to a traumatic event, with a focus on the potential moderating roles of PTSD and SUD diagnoses at the final assessment. Additionally, in attempt to better understand the functional relationship between PTSD symptoms and substance use posttrauma, this study compared models reflecting the theories of self-medication, susceptibility, and mutual maintenance. Participants included 137 individuals who had experienced a traumatic event within 6 months prior to study enrollment. Participants completed four assessments over an approximate 1-year period that included clinician-administered measures for DSM-5 PTSD symptoms and SUD diagnosis and self-report measures of alcohol and drug use. Change over time in PTSD symptoms and substance use by diagnostic status were investigated using growth curve models. Temporal sequencing between PTSD symptom severity and substance use was investigated with bivariate latent difference score structural equation modeling. In line with the conceptualization of PTSD as a disorder of impeded recovery, having a diagnosis of PTSD at the final assessment moderated the trajectory of PTSD symptom severity such that symptom severity declined only among those without PTSD. In contrast, the influence of SUD appeared to be negligible. Both PTSD and SUD diagnoses were associated with initial drug use frequency. However, the relationship between alcohol use and diagnostic status did not reach statistical significance. Regarding temporal relationships between PTSD symptoms and substance use, significant and negative PTSD to change in substance use cross-lagged paths were found across most of the models, while only one significant substance use to change in PTSD severity crosslagged path emerged in the PTSD intrusion with alcohol use model. These results add to a growing body of research suggesting trauma-focused intervention is viable for individuals with PTSD/SUD. Further, examination of potential mediators and moderators of the relation between PTSD and SUD is recommended as a critical focus for future research.
0949 The Relationship between Heavy Alcohol Use and Insomnia on PTSD Symptom Severity
