Delusional Infestation: A Retrospective Cohort Study of 49 Patients Over A 6-Year Period.

Delusional infestation (DI) is the fixed false belief of pathogenic infestation of the skin or body despite no supporting medical evidence. It is a relatively rare condition with a reported prevalence of 1.48 per 1 million people. Successful treatment can be challenging as patients are often reluctant to accept referral or involvement of psychiatric services. We report a retrospective cohort study of 49 consecutive patients with a diagnosis of DI, assessed in a regional psychodermatology service over a 6-year period. Low dose antipsychotics (risperidone or olanzapine) were prescribed in 44 patients. We use our data to explore possible reasons why DI can be challenging to treat. Response to treatment and engagement with services is multifactorial. Our study emphasises the importance of early assessment and supports the expansion of psychodermatology services in the United Kingdom.