Developing Memory Reconsolidation Blockers as Novel Posttraumatic Stress Disorder (PTSD) Treatments

Inclusion Criterion: * Participant has experienced a traumatic event that meets the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV)11 A1. and A.2. PTSD criteria * Participant currently meets DSM-IV criterion B.5, viz., "physiological reactivity on exposure to internal or external cues that symbolize or resemble an aspect of the traumatic event." Exclusion Criteria: * Medical condition that contraindicates the administration of mifepristone, e.g., history of adrenal failure; concurrent corticosteroid therapy; hemorrhagic disorders; cardiovascular, hypertensive, hepatic, respiratory or renal disease; insulin dependent diabetes mellitus; severe anemia; heavy smoking; porphyria; allergy to mifepristone; concurrent anticoagulant therapy; or medical condition that contraindicates the administration of DCS e.g., hypersensitivity to cycloserine, epilepsy, severe renal insufficiency. * Pregnant (as determined by mandatory blood pregnancy testing, or currently breast feeding. (Note: Women who have had a hysterectomy or are post-menopausal (defined as over the age of 50 with no menstrual period for at least 12 months) will be exempted from pregnancy testing. Furthermore, women of childbearing potential will only be included if: a) they are using contraception in the form of barrier methods with spermicide, hormonal methods (e.g. birth control pill), or intrauterine devices (IUDs), or b) they have not been sexually active for the preceding 60 days.) * Contraindicating psychiatric condition, e.g., current psychotic, bipolar, melancholic, or substance dependence or abuse disorder; or currently suicidal. * Cognitive Impairment or dementia * Initiation of, or change in, psychotropic medication within one month prior to recruitment * Current use of medication that may involve potentially dangerous interactions with mifepristone, including certain CYP 3A4 substrates such as calcium channel blockers, azole antifungals, macrolide antibiotics, and tricyclic antidepressants. (Note - we have not included in this list benzodiazepines or selective serotonin reuptake inhibitors, because these drugs are frequently used by PTSD participants, and they have sufficiently wide therapeutic ranges such that any transient increases in blood levels induced by a single dose of mifepristone will not endanger participants); or current use of medication that may involve potentially dangerous interactions with DCS, including ethionamide, isoniazid, and pyridoxine. * Inability to understand the study's procedures, risks, and side effects, or to otherwise give informed consent for participation; * Age less than 18.