Domain-specific cognitive course in schizophrenia: Group- and individual-level changes over 10 years

Cognitive impairments in schizophrenia are well-documented, present across several cognitive domains and found to be relatively stable over time. However, there is a high degree of heterogeneity and indications of domain-specific developmental courses. The present study investigated the 10-year cognitive course in participants with first-episode schizophrenia (FES) and healthy controls on eight cognitive domains and a composite score, looking at group- and individual-level changes. A total of 75 FES participants and 91 healthy controls underwent cognitive assessment at baseline and follow-up. Linear mixed models were used for group-level analyses and reliable change index (RCI) analyses were used to investigate individual change. The prevalence of clinically significant impairment was explored at both time points, using a cut-off of < -1.5 SD, with significant cognitive impairment defined as impairment on ≥2 domains. Group-level analyses found main effects of group and time, and time by group interactions. Memory, psychomotor processing speed and verbal fluency improved, while learning, mental processing speed and working memory were stable in both groups. FES participants showed deteriorations in attention and cognitive control. Individual-level analyses mainly indicated stability in both FES and controls, except for a higher prevalence of decline in cognitive control in FES. At baseline, 68.8 % of FES participants had clinically significant impairment, compared to 62.3 % at follow-up. We mainly found long-term stability and modest increases in cognition over time in FES, as well as a high degree of within-group heterogeneity. We also found indications of deterioration in participants with worse cognitive performance at baseline.