Nestor Girala
The efficacy of hallucinogenic drugs (ayahuasca, psilocybin, LSD, ketamine) in treating depression and addictions is accompanied by intense emotional states and mystical-type experiences, including feelings of oneness, transcendence, ineffability, and awe. These common psychopathological elements may mediate the drugs' therapeutic action. The paper reviews literature on subjective experiences during such treatments and compares them with other life-changing experiences, discussing the evolutionary value of these emotions for group cohesiveness and the recalibration of cognitions and emotions.
Viviana D. Evans, Alejandro Arenas, Kenneth Shinozuka et al.
preprint
Ketamine, originally a dissociative anesthetic, is now used for treatment-resistant depression and major depressive disorder with suicidal ideation. A single intravenous infusion shows antidepressant effects within hours, with a large effect size on depression scores. It also reduces PTSD symptom severity and suicidal ideation in emergency settings. However, therapeutic effects often subside within weeks, requiring repeated doses. Risks include temporary or persistent memory impairment, cardiovascular issues, liver toxicity, and bladder inflammation. Ketamine's opioid-sparing effect improves postoperative pain management.
SSRN Electronic Journal
Michael Alvear
A synthesis of 31 studies from 2016 to 2026 finds that intravenous ketamine rapidly reduces suicidal ideation, with 63% of patients achieving full remission by Day 3 compared to 32% on placebo, effects appearing within 40 minutes. Intranasal esketamine shows inconsistent results across studies, but when confounding factors such as hospitalization floor effects, insensitive measurement, and treatment resistance are accounted for, its anti-suicidal effect becomes clear and lasts up to 18 weeks. Injection routes show promise but lack randomized trial evidence. The analysis is based on a publicly available dataset.
Research Square
Alice Le Berre
In adults with treatment-resistant depression, esketamine was associated with early microstructural changes in the dentate gyrus of the hippocampus: reduced fractional anisotropy and increased orientation dispersion index, consistent with greater dendritic complexity. Lower baseline left-dentate gyrus fractional anisotropy correlated with greater improvement at two weeks, and a decrease in fractional anisotropy over that period also correlated with improvement. These changes suggest esketamine may promote hippocampal plasticity, and baseline diffusion MRI metrics could serve as candidate biomarkers for treatment response. The study included 12 adults with treatment-resistant depression and 24 matched controls, but larger studies are needed.
Michael Alvear
preprint
More than 25 systematic reviews and meta-analyses published between 2020 and 2025 on ketamine-based therapies for depression are summarized. Intravenous (IV) ketamine, esketamine nasal spray (Spravato), and oral ketamine show differences in response rates, remission rates, speed of symptom relief, and durability of results. The report also examines research on combining ketamine with psychotherapy. The evidence is drawn from high-quality peer-reviewed studies, including randomized controlled trials and observational studies, providing a clear overview of the most reliable evidence available.
European journal of psychotraumatology
December 1, 2026
Maud Rothärmel, Lila Mekaoui, François Kazour et al.
1 citation
In a retrospective study of 22 adults with treatment-resistant depression and comorbid post-traumatic stress disorder who received esketamine nasal spray, trauma re-experiencing episodes occurred during treatment sessions. For 16 patients (72.7%) these episodes disappeared as sessions progressed. Treatment was stopped for 6 patients (27.3%) due to re-experiencing. Among those who continued esketamine, depression response rate was 45.5% and remission 22.7%; PTSD improvement rate was 45.5% and remission 18.2%. The findings suggest esketamine can be safely administered in this comorbid population and that trauma re-experiencing does not prevent clinical improvement.
Journal of affective disorders
November 1, 2026
Lindsay L Benster, Jordan N Kohn, Benjamin Wade et al.
In a real-world comparison of two FDA-approved treatments for treatment-resistant depression, intranasal esketamine led to faster improvement than repetitive transcranial magnetic stimulation (rTMS). Over 90 days, esketamine patients responded a median of 36 days versus 49 days for rTMS, and suicidal ideation resolved more quickly (median 9 vs. 26 days). However, by about 90 days, overall response and remission rates were similar between the groups (68.8% and 45.2% for esketamine; 59.4% and 40.1% for rTMS), suggesting a difference in speed rather than ultimate effectiveness. For rTMS, slower response was predicted by comorbid anxiety and benzodiazepine use, while former tobacco use predicted faster response. No such predictors were found for esketamine.
Journal of affective disorders
November 1, 2026
Dian-Jeng Li, Tien-Wei Hsu, Te-Chang Changchien et al.
Patients with major depressive disorder who are prescribed esketamine have higher rates of comorbid substance use disorders compared to those treated with antidepressants or repetitive transcranial magnetic stimulation. Among esketamine users, those with a substance use disorder face greater risks of self-harm, suicide attempt, emergency visits, hospitalization, and mortality. The findings indicate a prescription bias toward patients with comorbid substance use disorders and highlight the need for careful monitoring and specialized care for this population.
Journal of affective disorders
September 15, 2026
Rutger Boesjes, Claudia Oosterveld, Jeanine Kamphuis et al.
1 citation
Ketamine and its enantiomers show rapid antidepressant effects for major depressive disorder and bipolar disorder, but responses vary widely. This systematic review of 26 studies (1694 participants) found that ketamine treatment is linked to improved subjective sleep quality. Preliminary evidence suggests that baseline sleep disturbances and early sleep improvements may predict antidepressant response. Some studies also indicate beneficial effects on objective sleep and circadian rhythmicity, but this finding is tentative due to few published articles. The authors call for more research on objective circadian measures and potential synergy with chronotherapies.
Psychiatry research
September 1, 2026
Isis Lunsky, Gilmar Gutierrez, Xena Wang et al.
Postpartum depression (PPD) is common and harmful if untreated, with few effective prevention strategies. Ketamine and esketamine are rapid-acting antidepressants showing promise for PPD. This review searched five databases for peer-reviewed randomized controlled trials, pilot studies, and observational studies examining ketamine or esketamine for PPD prevention during pregnancy or postpartum, for both cesarean and vaginal deliveries. A network meta-analysis and narrative synthesis were used. Thirty-six studies were identified; five included vaginal delivery, thirty included cesarean section, and one did not specify delivery mode. Results suggested that ketamine and esketamine were well tolerated and may reduce PPD risk. However, data quality was low to very low, so results should be interpreted cautiously. More high-quality studies are needed.