Cognitive performance in individuals with a first psychotic episode according to age at onset of psychotic symptoms and premorbid intelligence quotient

Abstract

Introduction: There is great variability in the cognitive performance profile, clinical presentation, course of symptoms, and subsequent functioning in individuals with a first episode of psychosis (FEP). Premorbid IQ (pIQ) and age of onset are two important prognostic factors relevant to clinical practice and broadly explored in psychosis research (1,2) that could help to explain heterogeneity in cognitive performance after FEP. Methods: The present prospective longitudinal (two-year) observational study examines the neurocognitive performance profiles of 255 individuals with FEP and 326 controls. Using ANOVA, we compared four FEP subgroups according to the following criteria: age of onset before or after 18 years old, and pIQ below or above 85. We examined cognitive changes in the subgroups with pair-wise comparisons, two-way mixed ANOVA, and repeated measures ANOVA. General objective: to characterize the neuropsychological profiles of the four subsets of individuals with a FEP defined by age of onset of psychosis (<18 or ≥ 18) and p-IQ (low or average) and to compare these subgroups’ neuropsychological performance, at baseline and at two-year follow-up. Results: The subgroups with early-onset and adult-onset low pIQ showed cognitive deficits more than 1 SD below the control mean and significantly different from early- and adult-onset average pIQ subsets at both the baseline evaluation and the two-year follow-up. These deficits were in attention and processing speed (p <0.001), working memory (p <0.001), verbal learning and memory (p <0.001), executive function (p <0.001), and global cognition (p <0.001). Cognitive performance in the early-onset average pIQ subgroup did not differ from that of the adults with average pIQ, and the former subgroup showed improved scores over time. Discussion: Our results suggest that the presentation of psychotic symptoms in patients with a lower than average pIQ is associated with a globally impaired profile. Estimating pIQ in the early stages of the disorder can help identify individuals who require early personalized neurocognitive intervention.