Comment

Shaping the renaissance of psychedelic research

Existing pharmacological treatments for psychiatric disorders have demonstrated limited efficacy, delayed onset of action, and significant burden of side effects. Recent findings from human studies with psychedelics have shown promise, demonstrating rapid and sustained clinical benefits of these compounds for a variety of psychiatric disorders. Classical psychedelics have a rich history and some of these compounds have been used in shamanic and spiritual ceremonies for millennia. The psychoactive effects of these drugs, particularly on human consciousness, have generated great scientific curiosity, and early research on psychedelics suggested their clinical benefits for psychiatric conditions, including alcohol use disorders and anxiety and depressive symptoms in terminal illness and life-threatening conditions. Since the 1990s, after a period of dormancy that followed the criminalization of psychedelic drugs since the Controlled Substance Act of 1970, the continued interest in their unique psychoactive effects along with the pursuit for novel and more effective treatments in psychiatry have led to a renewed interest in research on these compounds. While preliminary findings on psychedelics are encouraging, current evidence is still insufficient to support extensive use of these drugs routinely. Long-term safety and efficacy of these compounds remain unclear, and several clinical trials are underway and may add clarity to these questions. Therefore, this article intends to provide an overview of the evidence to date on psychedelic drugs – particularly psilocybin, MDMA, and LSD – for the treatment of psychiatric disorders.

The use of psychedelic treatments has shown very promising results in some psychiatric and addictive disorders, but not all patients achieved a response.

The aim of this review is to explore the clinical and biological factors which could predict the response to psychedelics in psychiatric and addictive disorders.

A systematic research was performed on MEDLINE, PsycInfo, Web of science, and Scopus databases from January 1990 to May 2020. All studies investigating the predictive factors of response to psychedelics regardless of psychiatric or addictive disorders, were included.

Twenty studies investigating addictive disorder, treatment-resistant depression, obsessive-compulsive disorder and depressive and anxiety symptoms in patients with life-threatening cancer were included in this review. We found that, in all indications, the main predictive factor of response to psychedelics is the intensity of the acute psychedelic experience. Indeed, we found this factor for alcohol and tobacco use disorders, treatment-resistant depression, and anxiety and depressive symptoms in patients with life-threatening cancer, but not for obsessive-compulsive disorder.

The intensity of the acute psychedelic experience was the main predicting factor of response. The action mechanism of this experience was not clear, but some hypotheses could be made, such as a modulation of serotoninergic system by 5-HT2A receptors agonism, a modulation of the default mode network (DMN) with an acute modular disintegration of the DMN followed by a re-integration of this network with a normal functioning, or an anti-inflammatory effect of this treatment.

Though there was initial interest in the use of psychedelic drugs for psychiatric treatment, bad outcomes and subsequent passage of the Substance Act of 1970, which placed psychedelic drugs in the Schedule I category, significantly limited potential progress. More recently, however, there has been renewal in interest and promise of psychedelic research. The purpose of this review is to highlight contemporary human studies on the use of select psychedelic drugs, such as psilocybin, LSD, MDMA and ayahuasca, in the treatment of various psychiatric illnesses, including but not limited to treatment-resistant depression, post-traumatic stress disorder, end-of-life anxiety, and substance use disorders. The safety and efficacy as reported from human and animal studies will also be discussed. Accumulated research to date has suggested the potential for psychedelics to emerge as breakthrough therapies for psychiatric conditions refractory to conventional treatments. However, given the unique history and high potential for misuse with popular distribution, special care and considerations must be undertaken to safeguard their use as viable medical treatments rather than drugs of abuse.