Psychotherapy Effects on Reward Processing in PTSD

The goals of the study are as follows: 1. Quantify, under conditions of safety (no threat), how PTSD psychotherapy alters reward circuit function and information encoding. 2. Identify how presence of threat augments PTSD psychotherapy effects on reward circuit function and information encoding. 3. (Exploratory). Identify how, following psychotherapy, changes in reward circuit function and information encoding under conditions of safety and threat are associated with improvements in symptoms of diminished positive affect (DimPA). To accomplish the goals of the study, the investigators propose a neuroimaging-coupled, randomized clinical trial of immediate vs. delayed individual cognitive processing therapy (CPT) in individuals (N=120) with a primary diagnosis of chronic PTSD. Individuals will undergo, prior to randomization, clinical and neurobiological assessment with functional magnetic resonance imaging (fMRI) during completion of several reward processing paradigms. Two of these involve both a normal "safe" context and a threat context manipulation (threat of mild electrodermal shock that is periodically cycled throughout the task). Another paradigm involves making decisions to either approach reward or forego a reward when this decision conflicts with the likelihood of an aversive outcome. This is known as approach-avoidance conflict (AAC). This battery will provide a comprehensive characterization of reward processing behavior and circuit function and establish its relationship to treatment processes, as well as how such processes may vary as a function of threat.