Increased occurrence of depression in psychosis-prone subjects: A follow-up study in primary care settings

A follow-up survey was performed with a network of general practitioners (G Ps) to examine whether a higher proneness for psychosis predicts a greater incidence of depression in subjects with no history of mood disorder. At th e first stage of the survey (T1), a self-report questionnaire exploring del usional ideation (Peters et al. Delusional inventory [PDI-21]) was administ ered to the patients of the GPs. Information on psychiatric status at the b aseline and conclusion of the 12-month follow-up period was provided by the GPs. The present study was restricted to 425 subjects with no lifetime his tory of depression. An incident depression was diagnosed in 18 subjects. Mo st items exploring delusional beliefs and hallucinations were more frequent ly endorsed by subjects with incident depression. Subjects with a PDI-21 sc ore above the 90th percentile at T1 were nine times more likely to present with an incident depression during the follow-up period than those with PDI -21 scores below the 10th percentile. Psychosis proneness is associated wit h a greater risk for depression, suggesting that a continuum of vulnerabili ty may exist between affective disorder and nonaffective psychosis. Copyrig ht (C) 1999 by W.B. Saunders Company.