Twin study of illness history variables in psychosis.

Journal article

BACKGROUND: Genetic factors are important in the aetiology of psychotic disorders, but it is unclear how far they influence aspects of illness history within psychoses. AIMS: To investigate the extent, and type of familial aggregation for a range of illness history variables in psychosis. METHODS: Two-hundred-and-twenty-four proband-wise twin pairs (106 monozygotic, 118 same-sex dizygotic), where probands had psychosis, were ascertained from the Maudsley Twin Register in London. We investigated the following illness history variables, rated using the OPCRIT checklist: age at onset; chronicity of course; mode of onset; psychotic/affective predominance; pre-morbid social adjustment; and the presence of a psychosocial precipitant. We used Mx statistical modelling software to analyse correlations of variables within pairs of monozygotic twins concordant for psychosis; and relationships between variables in probands and risk of psychosis in monozygotic and dizygotic co-twins. RESULTS: There was a high monozygotic within-pair correlation for age at onset (intra-class correlation=0.9); moderate correlations for chronicity of course (polychoric correlation=0.4) and psychotic/affective predominance (polychoric correlation=0.5); and lower non-significant correlations for other variables. No variables consistently predicted risk of psychosis in co-twins. CONCLUSIONS: Illness history variables in psychosis show a broad range of familial aggregation. It is likely that familial influences are predominantly modifying effects, independent of susceptibility factors for psychosis.

Authors: Allan, C; Cardno, A; Rijsdijk, F; Kalidindi, S; Farmer, A

• Publication status: Published
• Journal: Schizophrenia research
• Volume: 115
• Issue: 2-3
• Pages: 237-244
• Publication date: 2009-12-01
• DOI: 10.1016/j.schres.2009.09.002
• EISSN: 1573-2509
• ISSN: 0920-9964
• Language: English
• Keywords: Checklist; Genetic Predisposition to Disease; Risk Assessment; Twins; Phenotype; Twin Studies as Topic; Diseases in Twins; Psychotic Disorders; Humans; Models, Statistical; Age Factors; Psychiatric Status Rating Scales; Sex Factors