Psychedelic-assisted psychotherapy for the treatment of major depression: a synthesis of phenomenological explanations.

Psychedelic-assisted Psychotherapy (PAP) combines the use of psychedelic compounds, such as psilocybin, with psychotherapy. PAP has shown some promise as a novel treatment for Major Depressive Disorder (MDD), and empirical research suggests that its efficacy turns on the altered states induced by psychedelic compounds. In this paper we draw on the literature of phenomenology to explain the therapeutic potential of psychedelic experiences. Svenaeus characterises mental illness as a form of suffering that entails three distinct but related experiences of alienation or "unhomelike being-in-the-world": (1) illness suffering, which relates to embodiment; (2) existential suffering, which relates to self-narratives, and (3) political suffering, which relates to social relationships. Ratcliffe further characterises the experience of MDD in phenomenological terms as a loss of pre-intentional possibility that manifests as excessive noematic feeling in the experience of embodiment, restrictive narratives in the construction of self, and disconnectedness in experience of the social world. We contend that PAP ameliorates the suffering associated with MDD by inducing and consolidating a state of broadened pre-intentional possibility-one that entails sudden, profound and enduring changes in embodiment, self-narratives, and social experience. We argue further that this phenomenological account is consistent with a bio-psycho-social model of mental health and illness, and we frame it as an argument supporting the plausibility of recent claims about treatment success. This helps to justify ongoing future empirical research in this setting.