A review of hallucinogens, MDMA, and ketamine for severe mental health disorders describes their mechanisms and clinical outcomes. Hallucinogens like LSD and psilocybin target 5-HT2A receptors, inducing perceptual shifts that aid therapy for depression and anxiety. MDMA influences serotonin, dopamine, and norepinephrine, alleviating PTSD symptoms by enhancing emotional engagement during psychotherapy. Ketamine, a glutamate receptor antagonist, rapidly relieves symptoms in treatment-resistant depression. These substances show promise for patients unresponsive to traditional treatments but require careful dosage, monitoring, and risk management to prevent abuse and adverse effects.
Chronic stress triggers depression by activating a gut-immune-brain pathway. In mice exposed to chronic restraint stress, gut microbiota changes caused small intestinal γδ T cells to migrate to the brain, where they released interleukin-17A (IL-17A). This IL-17A impaired a mitochondrial cleanup process called mitophagy in the hippocampus, leading to reduced energy production, damaged synapses, and depression-like behavior. Blocking γδ T cell migration, removing a key receptor on these cells, or giving the antidepressant arketamine all restored mitophagy and improved behavior. The findings identify a specific chain from gut microbes to immune cells to brain mitochondria that drives stress-induced depression, and point to arketamine as a potential treatment targeting this pathway.