Delusional Infestation is Typically Comorbid with Other Psychiatric Diagnoses: Review of 54 Patients Receiving Psychiatric Evaluation at Mayo Clinic

Objective: Delusional infestation, which encompasses both delusions of parasitosis and delusions of infestation with inanimate objects (sometimes called Morgellons disease), has been said to represent a distinct and encapsulated delusion, that is, a stand-alone diagnosis. Anecdotally, we have observed that patients with delusional infestation often have one or more psychiatric comorbid conditions and that delusional infestation should not be regarded as a stand-alone diagnosis. The purpose of this study was to identify whether patients with delusional infestation have psychiatric comorbid conditions. We therefore identified patients who had been formally evaluated in the Department of Psychiatry during their visit to Mayo Clinic. Method: We retrospectively searched for and reviewed the cases of all patients with delusional infestation seen from 2001 through 2007 at Mayo Clinic, Rochester, Minnesota, and who underwent psychiatric evaluation. The diagnoses resulting from psychiatric evaluation were analyzed. Results: During the 7-year study period, 109 patients seen for delusional infestation at Mayo Clinic were referred to the Department of Psychiatry, 54 (50%) of whom actually followed through with psychiatric consultation. Of these 54 patients, 40 (74%) received additional active psychiatric diagnoses; 14 patients (26%) had delusional infestation alone. Abnormal personality traits were rarely documented. Conclusions: Most patients with delusional infestation have multiple coexisting or underlying psychiatric disorders. Therefore, evaluation by a psychiatrist, when possible, is advised for all patients with delusional infestation. (Psychosomatics 2012; 53:258-265)