Treatment-resistant depression (TRD) challenges standard approaches, prompting a shift toward non-monoaminergic interventions like neuromodulation and glutamatergic agents. This narrative review examines the endocannabinoid system (ECS) as a potential common pathway for these treatments. Evidence indicates that repetitive transcranial magnetic stimulation (rTMS) and electroconvulsive therapy (ECT) increase endocannabinoids anandamide and 2-arachidonoylglycerol, correlating with clinical improvement. Ketamine and esketamine modulate CB1 receptors, while psilocybin restores 2-AG and enhances CB1 expression in mood-related brain regions. These findings suggest ECS modulation may unify diverse antidepressant mechanisms in TRD, offering a promising target for novel therapies.
Emerging clinical and preclinical evidence suggests that the therapeutic benefits of psychedelics for depression and anxiety may be separable from their consciousness-altering effects. Psychedelics produce profound brain changes, including suppression of the default mode network, leading to intense subjective experiences such as ego dissolution. These effects require extensive preparation and integration, exclude individuals with certain psychiatric vulnerabilities, and raise scalability concerns. Pharmacological strategies like serotonin 2A receptor antagonism and development of biased psychedelic analogues might retain therapeutic efficacy without psychedelic experiences. Preclinical data indicate that downstream molecular and network-level mechanisms could mediate therapeutic effects independently of subjective states. Confirming this dissociation could enable more scalable, accessible treatments for broader psychiatric populations.