Delusional Infestation, Psychiatric Comorbidity, and Dementia: A Review of 146 Swedish Patients

Delusional infestation is a rare but severe dermatopsychiatric disorder. The diagnosis is associated with great suffering for the patients and their relatives, as well as substantial use of healthcare resources. It has been observed that patients with delusional infestation often have psychiatric comorbid conditions. Neurodegenerative diseases like dementia have been reported to be associated, but only in a few case reports. An observational, retrospective search was conducted in the institutional database and all medical records of patients with a diagnostic ICD code in the range F40.0-F40.9 (i.e., phobic anxiety disorders) were collected. A total of 146 patients met the criteria of delusional infestation; 42% were observed to have a former or current psychiatric comorbidity. Half the group, 50%, had more than 1 concomitant psychiatric diagnosis; depressive and/or anxiety disorder was the most common (62%). Furthermore, 9.6% developed dementia during the investigation period. Psychiatric comorbid conditions are common in this patient group. Such conditions should be diagnosed and treated. Further, delusional infestation could be an early sign of dementia and if signs of cognitive impairment are noted, further investigations and follow-up regarding dementia are recommended.