About 30–50% of patients with major depression do not respond to two or more antidepressant trials, a condition called treatment-resistant depression (TRD). A narrative review of 60 studies found that glutamatergic agents such as intravenous ketamine and intranasal esketamine consistently produce rapid and clinically meaningful reductions in depressive symptoms. Augmentation with atypical antipsychotics also helps partial responders. Psychedelic-assisted therapies show sustained antidepressant benefits and affect biomarkers like BDNF and inflammatory markers. The findings suggest a shift toward personalized, mechanism-driven treatments for TRD, with ketamine and esketamine offering rapid relief for acute high-risk cases and psychedelics remaining experimental but promising as adjunctive options.
Intranasal esketamine substantially reduced depression severity in 210 patients with treatment-resistant depression treated in routine clinical practice. Depression scores improved markedly over three months, and men showed a modest advantage over women by the end of treatment, with lower depression ratings and higher rates of response and remission. Among patients under 65 years, sex differences were small and not statistically significant; among those 65 and older, men appeared to benefit more numerically, but this difference did not hold up after statistical correction and remains uncertain. Discontinuation rates and safety outcomes were similar between sexes. The authors call for future studies to examine hormonal, vascular, inflammatory, and other factors that might explain the observed sex differences.