Background : Psychedelic assisted psychotherapy (PAP) can improve treatment-resistant depression. Its usefulness in Parkinson's disease (PD) is unknown. PD patients may have problems adjusting to their chronic progressive neurological disease. A change from emotional avoidance to acceptance has been reported following psilocybin administration in patients with treatment-resistant depression.

Objective : To report for the first time the effect of psilocybin in a PD patient.

Methods : A non-depressed 43-year-old female with a 2-year history of PD presented with difficulty adjusting to PD, anxious ruminations and pessimism. The patient declined an increase in dopaminergic medication or the introduction of an anxiolytic. Therapeutic patient education was not beneficial. The patient received four sessions of high-dose PAP within one year. Neurological and psychiatric assessments were performed before and at one year follow-up using qualitative interviews and quantitative assessment of motor status, dispositional optimism, depression, anxiety, apathy, and well-being.

Results : PAP was well tolerated. It significantly improved the patient's overall pessimistic outlook on her future and decreased her anxious ruminations and worries about potential handicap due to PD. Her general well-being improved, as well as all psychometric scores except for the apathy scale. Motor status remained unchanged. Better acceptance of PD allowed her to accept pharmacological treatment adjustment.

Conclusions : PAP could be a safe and useful treatment for PD patients with dispositional pessimism and difficulties accepting their disease by promoting profound decentration from habitual thoughts and emotions, improving mood and PD acceptance. Randomized, controlled studies are needed to confirm this result.