Do PTSD symptoms and course predict continued substance use for homeless individuals in contingency management for cocaine dependence?

Homeless individuals ( n = 187) entering contingency management (CM) for cocaine dependence were assessed for PTSD diagnosis, and a subset of 102 participants reporting traumatic exposure also periodically completed a self-report measure of PTSD symptoms. Patients with PTSD in full remission at 6 months (end of active treatment) and 12 months (end of aftercare) used substances much less frequently during aftercare than those with no PTSD diagnosis. Those whose PTSD diagnosis improved to full remission status during active treatment, and remained in full remission at 12 months, also had superior substance use outcomes. Severity of PTSD symptoms at 6 months, but not baseline or 2 months, was associated with substance use across treatment phases. Substance use during aftercare, however, was better predicted by changes in PTSD symptom severity. Patients whose PTSD symptoms improved more during active treatment fared better during aftercare than those with less improvement. Findings suggest homeless individuals with comorbid PTSD entering CM for cocaine dependence are not necessarily at increased risk for substance use compared to those without the comorbidity. However, course of PTSD does predict substance use, with the potential for CM to be unusually effective for those who respond with substantial, lasting improvements in PTSD.