Cognitive predictors of longitudinal positive symptom course in clinical high risk for psychosis

Abstract

Background Clinical High Risk (CHS) for psychosis is a state in which positive symptoms are predominant but do not reach a level of severity that fulfils the criteria for a psychotic episode. The aim of this study has been to investigate whether cognition in subjects with newly detected CHR affects the longitudinal development of positive symptoms.

Methods Fifty-three CHR individuals fulfilling the criteria for attenuated positive syndrome in the Structural Interview for Prodromal Syndromes (SIPS) were included. At inclusion, all participants completed a neurocognitive battery consisting of tests measuring attention, verbal memory, verbal fluency, executive functions and general intelligence. Cognitive domain z-scores were defined by contrasting with observed scores of a group of matched healthy controls (n = 40). Associations between cognitive performance at inclusion and longitudinal measures of positive symptoms were assessed by using generalised linear models including non-linear effects of time. All regression models were adjusted for age and gender.

Results Overall, SIPS positive symptoms declined over the time period, with a steeper decline during the first six months. Deficits in executive functions were assossiated witn a higher load of positive symptoms at baseline (p=0.006), but also to a faster improvement (p=0.030), wheras those with poor verbal fluency improved more slowly (p=0.018).

Conclusion To our knowledge, this is the first study that follows CHR subjects by means of frequent clinical interviews over a sustained period of time. The study provides evidence of an association between executive functions, including verbal fluency, with the evolvement of positive symptoms.