Predicting SSRI Efficacy in Veterans With PTSD

This is a research study to examine the effectiveness of a brief screening method that may predict which people with posttraumatic stress disorder (PTSD) or depression are most likely to show a positive response to selective serotonin reuptake inhibitor (SSRI) medications. Participants will be recruited over approximately 5.25 years, until at least 94 participants complete the 17 week study.

Inclusion Criteria: 1. has a history of trauma exposure as defined by criterion A of PTSD in the DSM-5 2. meets diagnostic criteria for PTSD, subthreshold PTSD, or MDD as defined by DSM-5 3. study psychiatrist's judgment that SSRIs are an acceptable treatment option for the participant's presenting concerns, and 4. interest in starting a trial of an SSRI Exclusion Criteria: * current or past history of bipolar I disorder, schizophrenic or other psychotic disorders * current organic brain disorder including severe traumatic brain injury, factitious disorder, or malingering * pregnancy * major neurological problems * current moderate or severe substance use disorder * active risk to self or others * evidence of clinically significant hepatic or renal disease or any other acute or unstable medical condition that might interfere with safe conduct of the study * intolerance or hypersensitivity to sertraline * failed past trial of sertraline (confirmed by medical record review) * use of drugs that directly affect the serotonin system (e.g., SNRIs, antipsychotics) within 3 months of the study * use of an SSRI within 3 months of the study. Use of other psychotropic medications must have been stable for 3 months prior to enrollment and remain stable throughout participation * hearing impairment for 780 Hz tones * current enrollment in trauma-focused psychotherapy * for those participants who currently have a non-VA or VA psychiatrist or primary care provider who is willing to prescribe medications, they must be willing to sign a release of information (ROI) for study staff to communicate with their providers and the provider believes that including the participant in the study is potentially appropriate. * As discussed above, the investigators will inform the participant that the investigators will share the following information with their current relevant care provider: * information about the design of the study, inclusion and exclusion criteria, the participant's psychiatric and medical diagnoses as well as illness severity, as assessed in the screening evaluation, and any history of safety issues such as risk to self or others. * If the participant doesn't sign a release of release of information (ROI) to contact the provider, the participant will not be entered into the active study.