The bodily self from psychosis to psychedelics.

The sense of self is a core part of normal human consciousness, but it can be altered in psychiatric conditions like psychosis and in altered states induced by psychedelics. Using the Moving Rubber Hand Illusion with 75 participants—patients with psychosis, people with substantial psychedelic experience, and controls—the study tested how these experiences affect the bodily self. Psychosis patients showed reduced Body Ownership and Sense of Agency during voluntary movement. The psychedelic group reported long-lasting subjective changes to selfhood, but no differences from controls appeared on the bodily-self measures. Thus, while psychedelics alter the subjective sense of self, these changes do not manifest at the bodily level, whereas bodily self-processing linked to voluntary action is disrupted in psychosis.

Study at a glance

Abstract

The sense of self is a foundational element of neurotypical human consciousness. We normally experience the world as embodied agents, with the unified sensation of our selfhood being nested in our body. Critically, the sense of self can be altered in psychiatric conditions such as psychosis and altered states of consciousness induced by psychedelic compounds. The similarity of phenomenological effects across psychosis and psychedelic experiences has given rise to the "psychotomimetic" theory suggesting that psychedelics simulate psychosis-like states. Moreover, psychedelic-induced changes in the sense of self have been related to reported improvements in mental health. Here we investigated the bodily self in psychedelic, psychiatric, and control populations. Using the Moving Rubber Hand Illusion, we tested (N = 75) patients with psychosis, participants with a history of substantial psychedelic experiences, and control participants to see how psychedelic and psychiatric experience impacts the bodily self. Results revealed that psychosis patients had reduced Body Ownership and Sense of Agency during volitional action. The psychedelic group reported subjective long-lasting changes to the sense of self, but no differences between control and psychedelic participants were found. Our results suggest that while psychedelics induce both acute and enduring subjective changes in the sense of self, these are not manifested at the level of the bodily self. Furthermore, our data show that bodily self-processing, related to volitional action, is disrupted in psychosis patients. We discuss these findings in relation to anomalous self-processing across psychedelic and psychotic experiences.