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Comparing the Neural Correlates of Psychedelics, Meditation, and Hypnosis

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Human beings of all cultures have been seeking altered states of consciousness (ASCs) since time immemorial. As a matter of fact, it has been posited by Ronal Siegel in his magnum opus Intoxication that our need to use mind-alter substances to induce ASCs has so much force and persistence that it functions almost like our drive for food, sleep, and sex.

In recent years, the therapeutic use of ASCs has become increasingly relevant in the treatment of various psychiatric disorders, thanks in part to the psychedelic renaissance. The phenomenology of psychedelics has often been compared to other ASC methods that do not require the ingestion of mind-altering substances, such as meditation, but also hypnosis. Yet, no study to date has made a direct comparison of these when it comes to their so-called ‘neural correlates’, which generally refers to the neural representation of a subjective experience. A recent study sought to address this knowledge gap in the literature by comparing resting state functional connectivity of psilocybin, LSD, meditation, and hypnosis in order to establish the neural correlates of each ASC method.

One of the most striking results of the study is that there was no common network in all four ASC methods, despite their significant phenomenological overlap. Perhaps this is due to the prominence of ineffability that is an inextricable part of ASCs, something that ultimately hints towards the fallibility of human self-report. Furthermore, the study shows that the direct comparison between hypnosis and meditation is associated with significant differences in functional connectivity and also differ when both of them are directly compared to either psilocybin or LSD. A final finding of the study, which might come as no surprise to some of you readers, is that psilocybin and LSD show no differences in functional connectivity when directly compared to each other. However, some results also suggest that they do show distinct relationships between their respective behavioral and neural correlates. In other words, this indicates that there are some discrepancies between the neural representation and what someone experiences subjectively when comparing psilocybin and LSD.

Overall, the authors conclude that the current results extend our understanding of the underlying mechanisms of ASCs. Most importantly, it highlights the clinical importance of investigating how ASCs can be utilized most effectively in the treatment of psychiatric disorders. Even though the current study looked at the acute effects of ASCs, there is increasing evidence that these are necessary for their enduring therapeutic effects. Although some researchers like Dr. David Olson argue to the contrary, a recent study caught my eye that further corroborates this view. Specifically, it demonstrated significant antidepressant effects two weeks following psilocybin that were correlated with increases in theta power,  an effect that is similarly observed following the practice of meditation and is accompanied by feelings of peace or blissfulness and low thought content.

But I digress… Ultimately, if we want to increase the efficacy of psychedelic-assisted therapy, the authors argue that it is of vital importance to understand the relationship between the acute effects of ASCs and the enduring therapeutic response given the observation that there is substantial variability in the acute response in psychedelics and that this acute experience can be shaped according to an individual’s set, setting, and dose. Accordingly, it is important to establish the acute neural correlates of various ASC methods in healthy controls, as it could contribute to the development of clinical biomarkers and map specific mechanisms of action to either a disease area or individual patient. Finally, given the observation that psilocybin, LSD, meditation, and hypnosis engage in distinct brain circuits, they could have potential synergistic properties that further facilitate the therapeutic response.

Read the full publication here!

Image via Dall-E

Stephan Tap

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