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 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 emphasizes the importance of early assessment and supports the expansion of psychodermatology services in the UK. We report a retrospective cohort study of 49 consecutive patients with a diagnosis of delusional infestation (DI) assessed in a regional psychodermatology service. We summarize patient outcomes and explore possible reasons why DI can be so challenging to treat. To our knowledge, this is the first published cohort study of this number of patients with DI over a 6-year follow-up period.