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Psychosis risk as a function of age at onset : A comparison between early- and late-onset psychosis in a general population sample.

Köhler S, van Os J, de Graaf R, Vollebergh W, Verhey F, Krabbendam L

Dept. of Psychiatry and Neuropsychology, Sth Limburg Mental Health Research and Teaching Network, EURON, Maastricht University, P.O. Box 616 (VIJV), 6200, MD, Maastricht, The Netherlands, l.krabbendam@sp.unimaas.nl.

BACKGROUND: Little is known about late-onset psychosis (onset after the age 45 years) and how it relates to early-onset psychosis (before age 45 years). The aims of this study were to calculate the incidence of non-affective, non-organic psychotic symptoms across the life span and to explore the contribution of different sets of risk factors in relation to age at onset. METHODS: Data were obtained from the three measurements of the Netherlands Mental Health Survey and Incidence Study. Symptoms of psychosis were assessed in individuals aged 18-64 years using the Composite International Diagnostic Interview. All individuals reporting first-onset of psychotic symptoms within a three-year interval were included. The degree to which sets of risk factors affected the psychosis outcome similarly across age groups was assessed. RESULTS: The number of subjects displaying incident psychotic symptoms was similar across age groups. Cumulative incidence rates ranged from 0.3% to 0.4%. Age differences were found for life-time depressive symptoms (risk difference = 5%, 95% CI = 1%, 9%) and baseline neuroticism (risk difference = 3%, 95% CI = 0%, 6%), indicating that late-onset psychosis was less often preceded by these. In contrast, no effect modification by age was observed for female sex, hearing impairment, being single, or life-time cannabis use. CONCLUSIONS: Onset of psychotic symptoms in late life is no rare event. Compared to early onset psychosis, the late-onset counterpart less often arises in a context of emotional dysfunction and negative affectivity, suggesting qualitative differences in aetiology and more effective premorbid coping styles.

Published 19 March 2007 in Soc Psychiatry Psychiatr Epidemiol, 42(4): 288-94.
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