2. Patients receiving the CBT for PTSD plus TAU will manifest equivalent reductions in substance use severity (drug and/or alcohol) to patients in the IAC+TAU intervention conditions at both the three-month and six-month follow-ups. CBT and IAC are both active treatments targeting substance use symptoms. The CBT+TAU and IAC+TAU condition patients will exhibit greater reductions in substance use than patients in the TAU condition at both the three-month and six-month follow-ups.