The psychedelic renaissance: psilocybin, a breakthrough for treatment resistant depression?

Abstract

Treatment resistant depression (TRD) is frequently encountered in clinical practice. The lack of response of the condition to conventional medications and augmentation strategies has spawned the search for novel treatment approaches. Psychedelic medications used in conjunction with intensive psychotherapy, so-called psychedelic-assisted psychotherapy (PAP), have been evaluated in a limited number of studies as an alternative tactic. This psychedelic renaissance has seen psilocybin, a naturally occurring, potentially hallucinogenic substance occurring in some species of mushrooms, used as one exemplar. The definition of “treatment resistance” varies between different authorities, but there is general agreement that a minimum standard is failure to respond to at least two pharmacological agents from different classes used at a therapeutic dose for an adequate length of time. In the studies to date, more stringent definitions have mostly been applied. Each of the clinical evaluations finds that the addition of a single dose of psilocybin to the psychotherapeutic regimen produces a rapid and clinically significant decline in depressive symptomatology, which is mostly retained in follow-up evaluations out to 12 weeks or longer. Psilocybin was well tolerated with mostly mild to moderate side effects of elevated blood pressure, fatigue, lack of concentration, headache, lethargy, vertigo, feeling of physical or emotional weakness, decreased appetite, nausea, feeling dull, and being easily exhausted, which were transient. Hallucinogen persisting perception disorder (HPPD) has occasionally been reported, while there were few reports of suicidal ideation and behaviour. Psilocybin appears to offer the promise of rapid alleviation of resistant depressive symptoms, but further controlled evaluations are necessary before the drug can be given routinely.