The primary goal of this study is to improve the overall efficacy of cognitive processing therapy-cognitive-only version (CPT-C) in a sample of 130 active-duty service members through a variable length treatment. The study seeks to determine if some service members would benefit from a longer or shorter dose of treatment (4-24 sessions), and to identify which individuals are likely to require more, less, or the standard number of treatment sessions to reach good end-state functioning. Predictors of length of therapy and treatment outcome will be examined. Specifically, we will evaluate factors related to internalizing/externalizing traits, cognitive flexibility, inability to inhibit dysfunctional cognitions, and readiness to change as they are related to the number of treatment sessions required to treat patients to the point of good end-state functioning. Additional outcomes including alcohol use, psychosocial functioning, physical health, and sleep also will be evaluated.