Cannabidiol as a Treatment for PTSD and PTSD Comorbid With TBI

Inclusion Criteria: * Meets clinical criteria for Posttraumatic Stress Disorder (PTSD) as per Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) * TBI present (for PTSD+TBI subjects only) as per American Congress of Rehabilitation Medicine (ACRM) definition * Mild TBI (for PTSD+TBI subjects only) as per Ohio State University Identification Screener * Able to provide at least 2 locators * Able to provide informed consent * Confirmation that the participant is reliably domiciled * Agreement to abstain from all other cannabinoid use for the duration of the study * Willingness to use contraception if of childbearing potential. Exclusion Criteria: * History of open head injury * TBI within the last 6 months * Moderate or Severe TBI * SUD in the last 12 months other than mild AUD or nicotine use * Use of any cannabinoid containing product within the last 1 month * Positive urine drug screen (Positive for cannabinoids, amphetamine, cocaine, opioids) * Currently prescribed medications with possible CBD-drug interactions * Lifetime history of any psychiatric disorder with psychotic features, bipolar disorder * Exposure to trauma in the last 30 days, including police duty or military service * Psychotherapy for PTSD or other psychiatric conditions initiated within 2 months of screening * Not stable for at least 2 months on psychiatric medication, anticonvulsants, antihypertensive medication, sympathomimetic medication, estrogen replacement therapy, medications associated with neurogenesis, or steroid medication * Active suicide attempt within the past year * Current significant suicidality (assessed using the C-SSRS), any significant suicidal behavior in the past 12 months, or any history of serious suicide attempts requiring hospitalization, or current significant homicidality. * Neurologic disorder or systemic illness affecting CNS function (apart from TBI) * Major medical illness (i.e. cancer or infectious disease.) * Clinical diagnosis of anemia, advised by physician to avoid blood draws * Significant laboratory abnormalities, significantly impaired hepatic function, abnormalities in complete blood count or metabolic panel * Significant allergic reactions to the drug including cannabinoids or sesame oil * Pregnancy or lactation * Contraindication to MRI * Males and females who plan to conceive a child during or two weeks following the study * Active legal problems likely to result in incarceration within 12 weeks of treatment initiation * Has a high risk of adverse emotional or behavioral reaction (e.g., evidence of serious personality disorder, antisocial behavior, serious current stressors, and lack of meaningful social support). * Inpatient psychiatric treatment in past 12 months, with the exception of detox and extended ED stays.