Case Report: Repeated low doses of psilocybin reduce perceived symptom severity but fail to restore cognitive flexibility in a case of severe obsessive-compulsive disorder: an observational case study of identical twins

Background Obsessive-Compulsive Disorder (OCD) can present significant challenges to individuals mental health, characterized by intrusive thoughts and repetitive maladaptive behaviors. Recent research into alternative treatments has highlighted psychedelics, notably psilocybin, for their potential therapeutic benefits in various psychiatric disorders, including OCD. This case study evaluated the impact of self-administered, low-doses of psilocybin, commonly referred to as microdosing, on symptom reduction and cognitive flexibility in OCD, with a focus on identical twins discordant for the condition. Case presentation The study documents the experiences of one twin diagnosed with OCD who began a regimen of low-doses of psilocybin containing mushrooms, while the other twin, unaffected by OCD, served as a comparison. Case X was diagnosed with OCD by a general practitioner in the Danish healthcare system. Following years of severe OCD, case X began a self-medicated regimen consisting of psilocybin containing mushrooms, corresponding to 1–5 mg of psilocybin, every 3 rd day. The other twin, case Y, who remained unaffected by OCD, and did not take psilocybin containing mushrooms. Cognitive flexibility was evaluated in both cases using a set-shift task. The affected twin reported a notable reduction in OCD symptoms, along with improvements in emotional regulation and overall well-being. However, despite these symptomatic improvements, deficits in cognitive flexibility remained present compared to the unaffected twin. Conclusion This case study underscores the potential of low-doses of psilocybin as a promising avenue for mitigating symptoms of OCD. Nevertheless, the observed disparity in cognitive flexibility highlights the nuanced nature of OCD pathology, suggesting that while low-doses of psilocybin may alleviate certain symptoms, it may not fully address underlying cognitive impairments. Further research employing larger sample sizes and rigorous longitudinal designs is imperative to elucidate the mechanisms underlying the therapeutic effects of psilocybin low-doses in OCD, offering insights into its broader applicability as a treatment modality.