[Mental disorders in close relatives of patients with paranoid psychoses]

Genetics and delusional disorder

This article gives an overview of genetic research approaches and their application to delusional disorder. Most studies have been based on small samples and have had other methodological limitations, so it is not clear whether there is a genetic contribution to the aetiology of delusional disorder. It is unlikely that delusional disorder is strongly related genetically to affective disorder or schizophrenia, but more subtle relationships cannot be ruled out. The rarity of multiply affected families prohibits linkage studies and, to date, molecular genetic investigations have been mainly limited to small association studies of dopamine receptor polymorphisms. A range of considerably larger, epidemiologically rigorous studies is required, but the uncommonness and other features of the disorder put strong limitations on the prospects for ascertaining adequate samples.

A delusional disorder that occurred in one of a pair of monozygotic twins

The authors reported a pair of male monozygotic twins in one of whom a delusional disorder occurred, and discussed the etiology of that disorder. The analysis of the twins indicates the following: 1. The disposition for the delusional disorder might be related to a psychological tendency to experience a delusion that might be based on a genetic factor. This might be strengthened by the development of a hypersensitive personality (Kretschmer, E.) promoted by environmental factors. 2. A hypersensitive personality might be a significant risk factor for the delusional disorder.

Psychiatric illness in first-degree relatives of patients with paranoid psychosis, schizophrenia and medical illness

This study examines the respective morbid risk for psychiatric illness determined by the family history method in the first-degree relatives of medical controls and patients with delusional disorder (paranoid psychosis) and schizophrenia. The morbid risk for schizophrenia and schizoid-schizotypal personality disorder was significantly greater in the relatives of the schizophrenic patients than in those of the delusional disorder or medical control patients, but no difference in the risk for affective illness or alcoholism was found in the three groups of relatives. Paranoid personality disorder was significantly more common in the relatives of the delusional disorder patients than in those of the medical controls. These results support the familial independence of delusional disorder and schizophrenia.