Study 1

Individuals with PTSD and TEHCs matched on sex, age at exposure to trauma, trauma type (interpersonal vs. noninterpersonal) and duration, race, and ethnicity were recruited through advertisements and fliers. All participants met DSM-IV (32) PTSD criterion A1 for adult traumatic events, including vehicular accidents, sexual or physical assaults, and witnessing serious injuries or deaths. Medical history, review of systems, physical examination, and laboratory tests determined the health status of all participants.

Individuals with PTSD were included in the study only following clinician diagnosis of PTSD and a Clinician-Administered PTSD Scale (CAPS) (33) score ≥50. Full inclusion and exclusion criteria for individuals with PTSD appear in Table S1. TEHC exclusion criteria were any current or past Axis I disorder and a CAPS score >19, which is considered symptomatic (33). The New York State Psychiatric Institute Institutional Review Board approved all procedures, and all participants provided written informed consent for the trial, which was registered at clinicaltrials.gov (identifier {"type":"clinical-trial","attrs":{"text":"NCT01576510","term_id":"NCT01576510"}}NCT01576510). Eighty-five participants consented. A total of 43 individuals did not drop out and had both pre- and posttreatment MRI scans (24 of them receiving treatment) and were therefore included in the analyses. To enlarge variability in hippocampal volume pretreatment and in changes in hippocampal volume during treatment, we used the data of both individuals with PTSD receiving PE and of TEHC individuals not receiving treatment. Thus, the TEHCs served as a control to expand heterogeneity in hippocampal volume variance, enabling the capture of potential associations if they indeed exist. The sample for study 1 overlaps with the sample of Rubin et al. (4).