Shared psychotic disorder in delusional parasitosis

Area of Science:

• Psychiatry
• Psychology
• Dermatology

Background:

• Delusional parasitosis (DP) is a condition where individuals have a fixed, false belief that they are infested with parasites.
• Shared psychotic disorder (SPD), also known as folie à deux, occurs when a delusion or mental disorder is transmitted from one individual to another.
• DP is associated with SPD in 5-15% of cases, yet systematic information on this comorbidity is limited.

Purpose of the Study:

• To systematically review and analyze published cases of delusional parasitosis associated with shared psychotic disorder.
• To compare the characteristics of patients with DP and SPD, their inducers, and DP patients without induced psychosis.
• To investigate diagnostic differences and treatment outcomes in DP-SPD dyads.

Main Methods:

• A comprehensive review of published case histories involving delusional parasitosis was conducted.
• 68 case histories of SPD were identified and analyzed.
• Data from SPD patients, their inducers (n=44), and DP patients without induced psychosis (n=1,155) were compared.

Main Results:

• Shared psychotic disorder was identified in 5.67% of reviewed DP cases.
• The sex ratio was balanced in the SPD group, contrasting with a female preponderance in other DP groups.
• SPD patients and their inducers more frequently reported visual hallucinations, with a 93% remission rate when separated from the inducer.

Conclusions:

• Delusional parasitosis and shared psychotic disorder share common features, particularly visual hallucinations.
• Separation from the inducer is a highly effective intervention for shared psychotic disorder in the context of delusional parasitosis.
• No significant diagnostic differences were observed between DP inducers and DP patients who did not transmit their delusions.