Psychedelics, entactogens and psychoplastogens for depression and related disorders

Currently, the most actively investigated rapidly acting antidepressants, anxiolytics and/or anti PTSD agents, include psychedelics e.g. psilocybin, LSD, N,N-dimethyltryptamine, ayahuasca; non-hallucinogenic entactogens, e.g. MDMA; psychoplastogens which rapidly promote neuroplasticity, e.g. ibogaine, ketamine and esketamine; and other atypicals e.g. dextromorphan/bupropion, esmethadone. Late-stage clinical trials support psychedelics and/or MDMA-assisted psychotherapy as rapidly acting treatments for major depressive disorder (MDD), treatment-resistant depression (TRD), PTSD or generalised anxiety disorders (GAD). Psilocybin, MDMA and LSD were granted FDA breakthrough status for TRD/MDD, PTSD and GAD, respectively, although FDA recently rejected the new drug application of MDMA in PTSD. Most of these drugs target the 5-HT and monoamine systems. Classical psychedelics act as 5-HT_2A receptor agonists, although LSD, DMT and psilocybin target other 5-HT and/or dopamine receptors. Psychedelic-dependent 5-HT_2A receptor agonism also has profound anti-(neuro)inflammatory effects. Advanced imaging studies suggest that brain 5-HT levels are reduced in depression. Functional magnetic resonance studies show that neural networks (cortico thalamic, salience, default mode) are profoundly impaired in depression. Such network defects are corrected upon psychedelic/entactogen treatment, offering a unique opportunity to serve as biomarkers for depression, anxiety and PTSD precision medicine trials. Psychedelics and entactogens target common end pathways, namely neuroplasticity/synaptogenesis, either directly via monoamine or glutamate receptors and/or indirectly, via BDNF and mTORC1 pathways. Together, these findings strongly support a biological basis for MDD, GAD, PTSD and related conditions, which can be considered as mixed biochemical, neurological and neuroimmune disorders, and are profoundly modified by psychedelics, entactogens and the newly developed psychoplastogens. LINKED ARTICLES: This article is part of a themed issue Emerging Therapeutic Opportunities for Psychedelic and Related Drugs. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v183.14/issuetoc.