When the comorbidity between PTSD and substance use disorders during active study intervention was examined, PTSD changes were found to impact substance use outcomes. Specifically, PTSD severity reductions were associated with substance use disorder improvement, with minimal evidence of substance use reduction improving PTSD symptoms. The findings, derived from two different sets of analyses spanning week-to-week probability data and longitudinal follow-up data, support the self-medication model as applied to populations with comorbid PTSD and addictive disorders.
Moreover, as predicted, PTSD-targeted treatment (Seeking Safety) was significantly more effective in achieving substance use improvement than the comparison group — but, only among those with heavy baseline substance use who had achieved significant PTSD reductions. Indeed, Seeking Safety is an integrated cognitive behavioral approach that actively links PTSD symptoms with “unsafe” substance use behaviors and whose efficacy has been largely demonstrated with active substance users (21
). Accordingly, those in the sample who were abstinent at baseline may have benefited less from a focus on PTSD symptoms as related to substance use behaviors compared to those with active substance use. We further speculate that Seeking Safety was superior to the control condition for this group because those with more substance use also had more severe PTSD. In fact, baseline PTSD scores were statistically different among three levels of substance use defined by the maximum number of days of use (p < 0.05), such that those with heavy substance use at baseline had more severe PTSD. If substances are used to self-treat PTSD symptoms, then daily substance use may be considered a proxy for greater PTSD severity. This finding suggests that while for the average dually-diagnosed patient the additional benefits of PTSD-targeted interventions may be limited, PTSD-focused treatments like Seeking Safety offer an advantage to patients with more severe PTSD and substance use symptomatology.
Although only the subset of study participants with more severe baseline substance use appeared to benefit from the specific elements of Seeking Safety, this finding is in line with other treatment studies that show the largest treatment effects among those with the most severe problems (22
). Because the detection of mediation in clinical trials is inherently a low power endeavor, it would be expected that differences would be most clearly observed in the subset of the sample where the intervention effect is most powerful, namely those with a high level of the baseline treatment targets (i.e., higher levels of substance use).
Overall, our results have important clinical implications for treating women with comorbid PTSD and substance use disorders. The findings further contradict conventional wisdom that addressing trauma-related symptoms will negatively impact substance use recovery. Instead, we demonstrate that trauma-focused treatment can lead to improvements in substance use outcomes in the context of PTSD symptom reductions, without decreasing participant attendance. Thus, we contend that the most effective treatment models are those that address PTSD before substance use or simultaneously. We propose this course of treatment, in contrast to treatment commonly offered in substance abuse treatment settings that lack a trauma-focus, especially because of the high prevalence rates of trauma histories and PTSD among such patients.
Our study has several limitations. First, 40% of the sample was abstinent at baseline which restricted the variability in alcohol and drug outcomes and, thereby, could have diluted the overall treatment effect. This is particularly true with respect to alcohol outcomes, as the vast majority of the sample met drug abuse or dependence criteria, with or without concurrent alcohol abuse or dependence (91.2%). Therefore, the findings may not generalize to a primarily alcohol dependent sample. Second, the sample was entirely comprised of women, which precludes extrapolation of results to men. A third consideration is that the participants received study interventions while enrolled in substance abuse treatment; receiving additional treatment focused on managing addictive behavior may have influenced outcomes.
The present study is only the second attempt of which we are aware to examine and test the temporal course of PTSD and substance use disorder symptom change. These data afforded a unique opportunity to discriminate between different mechanisms of comorbidity due to repeated and longitudinal measurement of symptoms. Our results offer support for the self-medication model and an empirical basis for PTSD-focused and integrated interventions for improved substance use outcomes in patients with severe symptomatology. Future studies should investigate these issues with men and examine the efficacy of PTSD-focused treatments for patients with varied substance use patterns to determine if such treatments are superior for them, as well.