Intensive 7-day Treatment for PTSD Combining Ketamine With Exposure Therapy

Inclusion Criteria: * Male or female between the ages of 21-75 years. This age range was chosen to fit with prior samples in which no adverse effects of ketamine have been observed. Adults in the 18-20 ranges have been eliminated because previous experience indicates that they often lack the maturity to participate effectively in similar protocols. Females will be included if they are not pregnant and agreed to utilize a medically accepted birth control method (to include oral, injectable, or implant birth control, condom, diaphragm with spermicide, intrauterine device, tubal ligation, abstinence, or partner with vasectomy) or if post-menopausal for at least 1 year, or surgically sterile. * Able to provide written informed consent according to Yale HIC guidelines. * Able to read and write English as a primary language. * Diagnosis of PTSD, as determined by the Clinician Administered PTSD Scale (CAPS-5) (Weathers et al., 2013). * Must have a score of 50 or higher on the Clinician-Administered PTSD Scale (CAPS-5) at screening. * No more than mild Traumatic Brain Injury (TBI) according to a modified version of the Brief TBI Screen (Schwab, et al., 2006). * Must not have a medical/neurological problem or use medication that would render ketamine unsafe by history or medical evaluation. Exclusion Criteria: * Patients with a diagnostic history of bipolar disorder, schizophrenia or schizoaffective disorder or currently exhibiting psychotic features as determined by the Structured Clinical Interview for DSM (SCID) (First, et al. 2010); dementia or suspicion thereof, are excluded. Other DSM Axis I disorders are permitted as long as they are not considered primary disorders. * Patients with a history of antidepressant-induced hypomania or mania as determined by open-ended psychiatric interview. * Serious suicide or homicide risk, as assessed by evaluating clinician; A serious suicide risk will be considered an inability to control suicide attempts, imminent risk of suicide in the investigator's judgment, or a history of serious suicidal behavior, which is defined using the Columbia-Suicide Severity Rating Scale (C-SSRS) (Posner et al., 2011) as either (1) one or more actual suicide attempts in the 3 years before study entry with the lethality rated at 3 or higher, or (2) one or more interrupted suicide attempts with a potential lethality judged to result in serious injury or death. * Substance abuse or dependence during the 6 months prior to screening as determined by the Structured Clinical Interview for DSM (SCID). * Any significant history of serious medical or neurological illness. * Any signs of major medical or neurological illness on examination or as a result of electrocardiogram (ECG) screening or laboratory studies. * Lifetime history of psychoactive substance or alcohol dependence or substance or alcohol abuse (other than nicotine or caffeine abuse), or drinking more than 5 drinks/week during the last year. * Abnormality on physical examination. A subject with a clinical abnormality may be included only if the study physician considers the abnormality will not introduce additional risk factors and will not interfere with the study procedure. * A positive pre-study (screening) urine drug screen or, at the study physician's discretion on any drug screens given before the scans. * Pregnant or lactating women or a positive urine pregnancy test for women of child-bearing potential at screening or prior to any imaging day. * Positive HIV or Hepatitis B tests. This test will take place at the screening visit. Subjects will be invited back to the Yale Depression Research Program either for their next study visit or for a HIV/Hep debriefing session. A study physician will inform them in person of the results. They will be given access to counselling and advised of the appropriate next steps. * Has received either prescribed or over-the-counter (OTC) centrally active medicine or herbal supplements within 60 days of enrollment into the study. Subjects who have taken OTC medication or herbal supplements may still be entered into the study, if, in the opinion of the principal/co-investigator, the medication received will not interfere with the study procedures or compromise safety. * Any history indicating learning disability, mental retardation, or attention deficit disorder. * Known sensitivity to ketamine. * Body circumference of 52 inches or greater. * Body weight of 250 pounds or greater. * History of claustrophobia. * Presence of cardiac pacemaker or other electronic device or ferromagnetic metal foreign bodies in vulnerable positions as assessed by a standard pre-MRI screening questionnaire. * Donation of blood in excess of 500 mL within 56 days prior to dosing. * History of sensitivity to heparin or heparin-induced thrombocytopenia.