Predominance of symptoms over time in early-onset psychosis: a principal component factor analysis of the Positive and Negative Syndrome Scale.

BACKGROUND: Early-onset psychosis is a symptomatically nonspecific and heterogeneous entity composed of several diagnoses. This study examined the dimensional structure of symptoms and the temporal stability of this structure during a 6-month follow-up. METHOD: A principal component factor analysis of the Positive and Negative Syndrome Scale was conducted at baseline, 4 weeks, and 6 months in a sample of 99 first-episode psychotic patients (mean age = 15.5 years). RESULTS: The factor analysis produced a 5-dimension solution (Positive, Negative, Depression, Cognitive, Hostility) that explained 62.4% of the variance at baseline, 63.4% at 4 weeks, and 65.1% at 6 months. Negative dimension was the most consistent and stable over time and was predominant at baseline (23.9%) and at 4 weeks (25.7%). Depression was predominant at 6 months (31.1%). CONCLUSIONS: There is a stable 5-dimension structure of symptoms in early-onset psychosis with varying predominance of symptoms over time. Negative symptoms are a core feature of psychosis and are thus important diagnostic criteria.