Additional Study Information: We are currently enrolling individuals with post-traumatic stress disorder (PTSD) to participate in this research study. The purpose of this research study is to evaluate the effectiveness of an investigational medication, brexpiprazole, for PTSD. Eligible participants will be randomly assigned to receive either brexpiprazole, sertraline (also known as Zoloft), or a placebo (a pill without active study drug), or a combination of these. Additionally, participants will complete questionnaires and be monitored by a medical professional throughout the study. Some clinic visits will be conducted virtually via phone or video. Participants will be compensated for their time and be reimbursed for travel expenses to and from the clinic.