Review Describes Latest Findings on the Mechanisms of Psychedelic Drugs and Their Therapeutic Potential

In a 2021 review article in a special issue of the Journal of Neurochemistry devoted to “Psychedelics and Neurochemistry,” researcher Alaina M. Jaster and colleagues summarized recent findings on psychedelic drugs, including their potential as treatments for psychiatric disorders and the structural changes they produce in the brain. The review article focused on findings in humans and provided background context based on findings in animals, particularly rodents.

In the article, Jaster and colleagues write that psychedelics “have in common a battery of acute (within minutes to hours) effects in humans that include profound changes in processes related to perception, cognition, sensory processing, and mood.” They are not considered to be addictive, and recent research has identified fast-acting and long-lasting therapeutic effects of psychedelics, particularly for the treatment of depression and substance abuse.

While psychedelic drugs interact with the brain in complicated ways, the role of serotonin 5-HT2A receptors seems to be crucial to their effects. Psychedelics have classically been divided into two groups based on their chemical structures: phenethylamines (which include mescaline and its synthetic analog DOI) and tryptamines (which include psilocybin/“magic mushrooms,” DMT/ayahuasca, and ergolines like LSD, which are sometimes separated into a third category). The authors of the review highlight that other substances with different chemical structures that do not fit into this classification can also function as psychedelics. Examples include efavirenz and quipazine, which both activate serotonin 5-HT2A receptors and change rodent behavior in the same way that other psychedelic drugs do. These drugs are providing new directions for research into how psychedelics work at both serotonin 5-HT2A receptors and monoaminergic G protein-coupled receptors (GPCRs).

An image from the review article shows the effects of various psychedelic drugs on different receptors.

Rodent studies are often used to investigate how psychedelic drugs work. Rodent behaviors such as ear scratching and head twitching increase when the rodents are given drugs that have psychedelic effects in humans. These behaviors return to normal when rodents are given drugs that function as serotonin 5-HT2A receptor antagonists, preventing the stimulation of these serotonin receptors.

While it has been established that serotonin 5-HT2A receptors play an important role in the hallucinogenic effects of psychedelic drugs, how serotonin receptors are involved in some of the therapeutic effects of psychedelics, such as antidepressant effects and changes to synaptic plasticity, is not yet clear.

According to the review, “A number of studies in animal models as well as postmortem human brain samples from subjects with depression and controls has provided evidence that mood disorders occur in conjunction with a reduction in the density of dendritic spines, particularly in the frontal cortex.” Dendrites are the projections from the cell bodies of neurons upon which nerve endings from the axons of other neurons synapse. The surface of these dendrites is covered in mushroom-shaped spines that help create these synaptic connections. The review describes in vitro and in vivo research on mice that suggests that the psychedelics DOI, DMT, and LSD can remodel dendritic spines.

At a recent scientific meeting, researcher Javier González-Maeso, one of the authors of the review, described findings from a recent study of mice given DOI. The structure of the dendritic spines in the prefrontal cortex changed rapidly in these mice. They had also been conditioned to produce a fear response, and the extinction process to get rid of this learned fear was sped up in the mice given DOI. These effects occurred via the serotonin 5-HT2 receptors. The exposure to the psychedelic also affected the regulation of genes involved in synaptic assembly for days, suggesting that epigenetic-induced changes in synaptic plasticity may underlie some of the long-lasting therapeutic effects of psychedelics.

The review also addressed “microdosing,” the recreational practice of consuming small amounts of psychedelics such as psilocybin or LSD, based on the theory that amounts too small to create a hallucinogenic effect may instead produce therapeutic results. The authors find limited data to support microdosing. Most studies in humans and rodents have found no effect or, in the case of one rat study, a worsening of dendritic spine density following microdosing.

Psilocybin Comparable to Escitalopram in the Treatment of Depression

March 2, 2022 · Posted in Peer-Reviewed Published Data, Potential Treatments · Comment 
ingredient in magic mushrooms may treat depression

Four randomized, controlled clinical trials have established that psilocybin, the hallucinogenic compound in “magic mushrooms,” has anti-depressant effects. Recently, a phase 2 clinical trial compared the effects of psilocybin to a US Food and Drug Administration (FDA)–approved treatment for depression, the selective serotonin-reuptake inhibitor (SSRI) escitalopram. The study by Robin Carhart-Harris and colleagues was published in the New England Journal of Medicine in 2021.

The 59 participants in the 6-week study, which took place in the United Kingdom, had longstanding moderate-to-severe major depressive disorder. They were randomized to two groups. The psilocybin group received two separate doses of 25 mg of psilocybin 3 weeks apart, plus 6 weeks of daily placebo. The escitalopram group received two separate doses of 1 mg of psilocybin 3 weeks apart plus 6 weeks of daily oral escitalopram. (The small doses of psilocybin administered to the escitalopram group were assumed to have negligible psychiatric effects.) All participants were told they would receive psilocybin (though not the dose) in order to standardize their expectations.

In addition to the drug treatments, all participants also received psychological support, which consisted of monitoring immediately after the administration of the drugs (given the expectation that the 25mg dose of psilocybin would produce an “altered quality of conscious experience”), psychological debriefings, and an active listening session.

Psilocybin improved depression symptoms to a greater extent than escitalopram did. Among the participants, 70% of the psilocybin group responded to the treatment, compared with 48% of the escitalopram group. Remission occurred in 57% of the psilocybin group compared with 28% of the escitalopram group. These differences in the outcomes for the two groups were not statistically significant.

The FDA has designated psilocybin a “Breakthrough Therapy” for severe depression, which indicates that the therapy may be a substantial improvement over existing therapies for a serious condition. The designation is intended to speed up the drug development and review process.

The state of Oregon legalized psilocybin-assisted therapy in 2020.

Psilocybin May Improve Treatment-Resistant Depression

November 10, 2016 · Posted in Potential Treatments · Comment 

ingredient in magic mushrooms may treat depression

Psilocybin mushrooms

A small, uncontrolled study in the journal Lancet Psychiatry suggests that psilocybin, an ingredient in hallucinogenic mushrooms, relieved depression symptoms for up to three months in seven of 12 participants with unipolar depression that had not responded to at least two antidepressant medications.

Psilocybin has a different mechanism of action than typical treatments for depression. It activates 5HT2A serotonin receptors.

The participants, who had moderate to severe depression, were given two oral doses of psilocybin, a low dose (10mg) to establish the safety of the intervention, and a higher dose (25mg) seven days later. Psychedelic effects (anxiety, confusion, nausea, and headache) peaked within two to three hours and had dissipated by six hours after the intervention.

Depression began to improve within 24 hours after the 25mg dose. Depression symptoms were significantly improved by one week after the intervention. Eight of the 12 participants had a complete remission of their depression after one week, and this lasted the full three months in five participants. By the end of the three months, a total of seven of the 12 participants met the criteria for response to psilocybin.

The study’s authors, led by Robin L. Carhart-Harris, suggest that their preliminary results warrant more systematic investigation of psilocybin, but because there was no comparison group in this study, a large placebo effect cannot be ruled out.