Efficacy of Psychoactive Drugs for the Treatment of Posttraumatic Stress Disorder: A Systematic Review of MDMA, Ketamine, LSD and Psilocybin

Varker and colleagues frame the review by noting that standard first-line treatments for posttraumatic stress disorder (PTSD), such as trauma-focused cognitive behavioural therapy and EMDR, have substantial non‑response rates and barriers to access. They describe renewed clinical interest in drugs with psychedelic or hallucinogenic properties—specifically ketamine, MDMA, LSD and psilocybin—as potential adjuncts or alternatives for people who do not benefit from or cannot access conventional interventions. The introduction summarises putative mechanisms relevant to PTSD for each agent: ketamine’s glutamatergic actions and possible reversal of stress‑related synaptic deficits; MDMA’s serotonergic, oxytocinergic and cortisol effects that may reduce amygdala activity and enhance prosocial emotion and therapeutic alliance; and LSD and psilocybin’s serotonergic (5‑HT2A) activity with effects on affect, cognition and fear extinction observed in preclinical and clinical work. This review was commissioned by the Department of Veterans’ Affairs to assess the clinical evidence for MDMA, ketamine, LSD and psilocybin as stand‑alone treatments or in combination with psychotherapy for adults with PTSD. The authors sought to fill a gap in the literature by systematically identifying and appraising controlled trials and observational studies, and by grading the overall quality of the evidence to inform research and practice priorities.

The investigators conducted a systematic review following PRISMA guidance and framed the question using PICO (Population, Intervention, Comparison, Outcome). Both randomised controlled trials (RCTs) and observational studies were eligible. The population was adults with PTSD (diagnosis or validated cutoff score). Interventions comprised administration of MDMA, ketamine, LSD or psilocybin as stand‑alone or combined with other treatments. Comparators included any control condition (active or inactive), and outcomes were changes in PTSD symptoms or diagnostic status. Eligibility required English‑language, peer‑reviewed studies of adults (≥18 years) where a majority (≥50%) had PTSD and PTSD outcomes were reported. Exclusions encompassed non‑English reports, animal studies, protocol‑only papers, secondary analyses, group therapy, paediatric samples, and grey literature. The authors did not use route of administration, dose, or psychometric properties of measures as exclusion criteria. Searches covered EMBASE, MEDLINE (PubMed), PsycINFO and the Cochrane Library from inception to 18 October 2019. Keyword combinations included drug names (MDMA, LSD, psilocybin, ketamine, etc.) and PTSD terms combined with intervention/treatment terms. Screening used Covidence with two reviewers for title/abstract and full‑text stages; a blinded reviewer checked 10% of records and discrepancies were resolved by a third reviewer when needed. Data extraction was performed with a predefined template capturing trial and intervention details, participant characteristics, PTSD measures and main PTSD outcomes; one reviewer extracted data and a second checked them. Study quality and bias were assessed using a modified NHMRC checklist addressing treatment assignment, selection bias control, blinding of outcome assessors and use of standardised outcomes. Overall evidence quality was graded using GRADE (high, moderate, low, very low). The authors grouped trials by drug and by whether the drug was given alone or with psychotherapy for narrative synthesis.

From 2,959 records, after deduplication and screening the review identified nine eligible trials (five ketamine, four MDMA); no trials of LSD or psilocybin for PTSD were found. One initially eligible study was excluded because it was terminated early. Study designs comprised seven RCTs (several cross‑over), one pre‑post trial and one case study. Sample sizes were small (range 1–41), mean ages ranged roughly 26–52 years, and sex distribution varied across studies. Across the included trials there were five placebo arms (two active, three inactive), two MDMA dose‑comparison trials, and two trials without a comparator. Follow‑up periods were often short, particularly for ketamine stand‑alone trials. Ketamine as a stand‑alone treatment for comorbid PTSD and depression: Three studies used ketamine alone (one double‑blind cross‑over RCT, one pre‑post series of 15 veterans, and one single case). The RCT administered a single IV dose of ketamine 0.5 mg/kg versus an active placebo (midazolam 0.045 mg/kg); self‑reported PTSD symptoms were significantly reduced at 24 hours post‑dose for ketamine but CAPS scores did not differ at one week, and depression scores showed no between‑group differences at either timepoint. Adverse effects after infusion included transient dissociation, elevated blood pressure requiring beta‑blockade in some, blurred vision, dry mouth, nausea/vomiting and headache. The pre‑post trial delivered six infusions of 0.5 mg/kg over 12 days to 15 veterans and reported significant PTSD improvement with a reported PTSD remission rate of 80% and depression remission of 60% immediately post‑treatment; dissociative symptoms were transiently increased. The single case reported short‑lived subjective improvements that were not sustained at 14 days. Using GRADE, the evidence for ketamine as a stand‑alone treatment for comorbid PTSD and depression was rated "very low," reflecting small samples and methodological limitations. Ketamine combined with psychotherapy: Two small double‑blind RCTs evaluated a mindfulness‑based psychotherapy (TIMBER) plus a single sub‑anesthetic ketamine infusion (0.5 mg/kg) versus TIMBER plus saline. At 24 hours both groups showed decreased PTSD symptoms on CAPS and PCL with no significant between‑group difference. However, TIMBER‑K extended the duration of response: in one trial cross‑over from placebo to ketamine increased mean duration of response by about 24 days; in the other, the ketamine arm had a longer sustained response (mean 34.44 ± 19.1 days) than placebo (16.50 ± 11.4 days). Adverse event reporting was limited; two participants had mild transient nausea in one trial. The combined‑therapy evidence was graded "low." MDMA in combination with psychotherapy: Four double‑blind cross‑over RCTs of MDMA‑assisted psychotherapy were identified. Trial procedures were broadly similar: preparatory psychotherapy sessions, two 8–10 hour experimental sessions with MDMA or comparator, supplemental dosing ~2.5 hours into each session, and multiple integration sessions thereafter. In an early RCT (N = 20; MDMA n = 12, placebo n = 8) clinician‑rated PTSD and self‑reported stress responses decreased significantly more in the MDMA arm; post‑treatment CAPS indicated 10 MDMA recipients versus 2 placebo recipients no longer met PTSD criteria. A dose‑comparison trial among veterans and first responders randomised participants to 30 mg (active control), 75 mg or 125 mg; one month after the second session the 75 mg and 125 mg groups had significantly larger reductions in PTSD severity than 30 mg, with large effect sizes. Of 24 participants completing 12‑month follow‑up in that study, 16 (67%) were not diagnosed with PTSD. There was one serious adverse event possibly related to treatment (an acute increase in ventricular contractions in a participant with a baseline arrhythmia) who recovered without evidence of ongoing cardiac disease. Ot'alora and colleagues’ dose‑response trial reported intent‑to‑treat mean CAPS changes at endpoint of −26.3 for 125 mg, −24.4 for 100 mg and −11.5 for 40 mg; statistical significance was reached in per‑protocol analyses (p = .03), with Cohen’s d reported as 0.42 (125 mg) and 0.37 (100 mg). A smaller RCT (N = 12) found significant within‑group reductions in self‑reported PTSD symptoms post‑treatment, but no between‑group differences at 3 weeks; at 12 months 5 of 11 no longer met PTSD criteria. Reported acute reactions to MDMA sessions included elevated blood pressure, increased pulse and body temperature, jaw tightness, nausea, dizziness and transient mood changes; post‑session reactions included sleep disturbance and low mood. No drug‑related deaths were reported. Overall, the MDMA‑plus‑psychotherapy evidence was graded "moderate," reflecting consistent positive findings across small RCTs but some methodological limitations.

Varker and colleagues interpret the assembled evidence as limited but indicative of differential promise across agents and delivery approaches. No trials of LSD or psilocybin for PTSD were identified, so conclusions are restricted to ketamine and MDMA. The authors judged ketamine as a stand‑alone treatment for comorbid PTSD and depression to have "very low" quality evidence: although short‑term symptom reductions were observed in some studies, lasting responses were generally not demonstrated. When ketamine was combined with psychotherapy the evidence was stronger (graded "low"); ketamine appeared to extend the duration of treatment response by a matter of weeks in small pilot trials, but it is not possible to disentangle ketamine’s contribution from that of the psychotherapy given the trial designs. By contrast, the authors rated the evidence for MDMA‑assisted psychotherapy as "moderate." Across several similarly designed small RCTs MDMA combined with non‑directive supportive psychotherapy produced consistent reductions in PTSD severity on clinician and self‑report measures, and a substantial proportion of participants no longer met diagnostic criteria at follow‑up in some trials. The discussion summarises proposed mechanisms for MDMA’s therapeutic effects—facilitation of fear extinction and memory updating, enhanced cognitive flexibility and stronger therapeutic alliance from prosocial effects—and notes that overall safety data for moderate doses of pure MDMA in these controlled settings suggest a favourable risk‑to‑benefit profile, despite common transient adverse reactions and one serious cardiac event judged possibly related to treatment in a participant with pre‑existing arrhythmia. The authors also note that the US FDA has designated MDMA a breakthrough therapy for PTSD and that Phase III multisite trials are underway. The paper highlights several limitations that temper interpretation: small sample sizes, short or inconsistent follow‑up, frequent use of cross‑over designs with potential carry‑over effects (and in some cases non‑randomised treatment order), heterogeneous interventions and comparators, and limited adverse event reporting. Methodological limitations of the review itself are acknowledged: clinical trial registries were not searched, non‑English publications were excluded, reference lists were not hand‑searched, and no meta‑analysis was performed because of the small number and heterogeneity of trials. The authors conclude that psychedelic and psychoactive agents—particularly MDMA when paired with psychotherapy and, to a lesser extent, ketamine in combination with psychotherapy—warrant further well‑designed research to determine efficacy, optimal therapeutic integration and safety in PTSD populations.