Delusional parasitosis. A comparative study to late-onset schizophrenia and organic mental disorders due to cerebral arteriosclerosis.

Delusional parasitosis (DP) was found in about 7 of 10,000 psychiatric admissions. The comparison of patients suffering from DP (n = 20) with 170 cases of late-onset schizophrenia (LOS) and 120 patients diagnosed as organic mental disorder due to cerebral arteriosclerosis (CAS) showed more similarities of DP with organic than with schizophrenic disorders. In addition, the phenomenological analysis supports the classification of the majority of DP cases as organic mental disorders. Even careful analysis cannot always answer the question, whether the main symptoms of DP have to be classified as delusions, hallucinations or misidentifications.