A systematic review on clinical therianthropy and a proposal to conceptualize zoomorphism as a diagnostic spectrum

Clinical therianthropy involves the delusional belief that one transforms into an animal and assumes its characteristics. We conducted a systematic review and identified 77 published cases. Of the many theriotypes reported, 68 % involved transformations into canines. Men debuted at a significantly earlier age than women; duration ranged from days (25 %) to weeks (12 %), months (33 %), and years (31 %). Associated conditions included psychotic disorders (41 %), psychotic depression (24 %), bipolar disorder (18 %), and Cotard’s syndrome (12 %), while 16 % engaged in other-directed physical violence. Treatment resulted in full remission (58 %) and partial remission (33 %) of the symptoms of clinical therianthropy, although the associated conditions were often chronic in nature and overall prognosis tended to be poor. We also discuss the history and reported etiologies of clinical therianthropy and propose a ‘two-hit’ pathophysiological model involving cenesthesiopathy and delusion formation. Diagnostic, therapeutic and forensic implications are also discussed. Lastly, we provide suggestions for a diagnostic spectrum that includes clinical and non-clinical cases, the latter comprising therians, furries, otherkin, and other people who experience varying levels of identification with animals.