Neuroimaging in psychedelic drug development: Past, present, and future

Psychedelic therapy (PT) is an emerging paradigm with great transdiagnostic potential for treating a range of psychiatric disorders, including depression, addiction, eating disorders, post-traumatic stress disorder, and others. ‘Classic’ serotonergic psychedelics, such as psilocybin, lysergic acid diethylamide (LSD), N, N-Dimethyltryptamine (DMT) and 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT), form the main focus of this movement, but other substances including ketamine, 3,4-Methylenedioxymethamphetamine (MDMA) and ibogaine also hold promise. The development of these novel treatment modalities in the early 21st century has occurred concurrently with the wider use of advanced human neuroscientific research methods; principally neuroimaging. This has enabled assessment of drug and therapy brain effects with greater precision and quantification than any previous novel development in psychiatric pharmacology. We outline some of the major trends in existing data and suggest that the modern development of PT has benefitted greatly from the use of neuroimaging. Important gaps in existing knowledge are identified which can be addressed by future neuroimaging work, principally using combined Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI) methods, plus other adjunct techniques. Suggestions for future multimodal imaging studies are discussed, which would resolve some of these questions and provide a firmer foundation for the development of PT.