Decline in Cognitive Performance Between Ages 13 and 18 Years and the Risk for Psychosis in Adulthood: A Swedish Longitudinal Cohort Study in Males

CONTEXT Clear evidence from many prospective, population-based studies indicates that patients who develop psychosis in adulthood experienced various cognitive deficits during childhood and adolescence. However, it is unclear whether these deficits become more severe during adolescence. OBJECTIVE To assess the influence of cognitive developmental trajectories in adolescence and young adulthood on the risk for psychosis in adulthood. DESIGN Longitudinal cohort study. SETTING Academic research. POPULATION-BASED COHORTS Four population-based cohorts of adolescent boys and young men born in Sweden in 1953, 1967, 1972, and 1977, totaling 10 717 individuals, and followed up through December 31, 2006. EXPOSURE Scores on tests of verbal, spatial, and inductive ability at age 13 years and in equivalent tests at army conscription (age 18 years). MAIN OUTCOME MEASURE Hospital admissions for nonaffective or affective psychoses in adulthood. RESULTS A relative decline (compared with the unaffected population) in verbal ability between ages 13 and 18 years was associated with increased risk for schizophrenia and for other nonaffective and affective psychoses (adjusted hazard ratio for schizophrenia for an increase of 1 SD in verbal ability, 0.59; 95% CI, 0.40-0.88; P = .009). Decline between ages 13 and 18 years was a much stronger predictor of psychosis than the verbal ability score at age 18 years alone. The association remained significant after adjustment for urbanicity, parental educational level, and family history of psychosis and persisted when cases with onset before age 25 years were excluded, indicating that this was not a prodromal effect. CONCLUSIONS A relative decline in cognitive performance in adolescence and young adulthood, particularly in verbal ability, is associated with increased risk for psychosis in adulthood, and a relative decline in verbal ability between ages 13 and 18 years is a stronger predictor of psychosis than verbal ability at age 18 years alone. This suggests an impairment of late neurodevelopment affecting the acquisition of verbal skills in adolescent boys and young men who later develop psychosis.