Psychopathological syndromes and familial morbid risk of psychosis

Background - Familial liability in the functional psychoses had traditionally been examined by comparing mutually exclusive diagnostic categories. This study examines overlapping psychopathological dimensions in relation to familial morbid risk of psychosis. Method - We tested for associations between seven factor-analysis derived psychopathological dimensions and familial morbid risk of psychosis, in a sample of 150 patients with recent-onset functional psychosis and 548 of their first-degree relatives. Results - A syndrome characterised by affective blunting and insidious and early onset of illness, non-specifically predicted psychosis in the first-degree relatives, whereas a manic syndrome specifically predicted affective psychosis in the relatives. No other main effects were observed, but there were interactions with proband diagnosis: a syndrome characterised by bizarre behaviour, inappropriate affect, catatonia and poor rapport predicted psychosis in relatives of schizophrenic probands, and a syndrome of depressive symptoms predicted psychosis in relatives of schizoaffective probands. Positive symptoms were not associated with illness in the relatives. Conclusions - Genetic effects in the functional psychoses may comprise non-specific components that canalise a general, early-onset, affective blunting phenotype and several other, more specific, influences on phenotypic variation.