Schizophrenia, Psychedelics, and Sense of Self: Comparison of Phenomenology and Neural Correlates

The relationship between schizophrenia and psychedelic drug states has long attracted scholarly interest and psychedelics have sometimes been described as psychotomimetic. Sense of self can be understood as the feeling of “mineness” that normally characterizes all experiences. In both schizophrenia and psychedelic experiences, alterations to sense of self are present and correlate with clinical measures. The phenomenology of altered sense of self in schizophrenia, often conceptualized as self disorder, and psychedelic experiences, often described as ego dissolution, has been noted since early twentieth-century descriptions and more recently been measured by psychometric scales. Both self disorder in schizophrenia and psychedelic states involve subjective alteration to the ordinary boundary between self and world. At the neural level, a limited number of neuroimaging studies have directly tested the associations of altered sense of self in schizophrenia and psychedelics; they have linked altered sense of self to differences in event-related potentials, regional cortical volumes, and functional connectivity. While one potential convergence was observed in EEG findings between schizophrenia and psychedelics, most results remain difficult to compare due to methodological differences. To address these challenges, the paper suggests development of a combined psychometric instrument that incorporates items from both schizophrenia- and psychedelic-focused scales, to be administered across schizophrenia, psychedelic, and control groups. This approach, supplemented by neuroimaging comparisons, could clarify the similarities and differences between these two forms of altered sense of self and their clinical relevance.