Exploring the Relationship between Cognitive Performance, Performance-Based Functioning, and Everyday Functioning in People with Schizophrenia: a Systematic Literature Review.

BACKGROUND AND HYPOTHESIS: Cognitive and functional impairments are core features of schizophrenia with considerable disease burden. However, the relationships between cognitive performance, functional capacity, and real-world functioning remain incompletely understood. This systematic review aimed to clarify the magnitude and nature of these interrelationships across primary research studies. STUDY DESIGN: A systematic review (PROSPERO CRD42024532729) was conducted across MEDLINE, Embase, PsycINFO, and Cochrane Database. Eligible articles assessed cognitive performance, functional capacity, and real-world functioning in adults with schizophrenia using standard psychometric instruments, and reported quantitative relationships between ≥1 of these constructs. Due to substantial heterogeneity in study designs, outcome measures, and reported metrics, a narrative synthesis was performed. STUDY RESULTS: Overall, 104 articles with unique datasets were included (88 observational, 16 interventional). The relationship between cognitive performance and functional capacity was the most studied (63/104 articles; 60.5%), with predominantly medium-to-large effect sizes. In contrast, associations between cognitive performance and real-world functioning were less frequently reported (43/104 articles, 41.3%) and largely small-to-medium, with only 2 large effect sizes identified. Associations between functional capacity and real-world functioning were variable (41/104 articles; 39.4%) and predominantly small-to-medium, with only 4 large effect sizes reported. Associations were less consistent when examined at the level of specific cognitive or functional domain. CONCLUSIONS: This review highlights the central role of cognition in shaping functional abilities, while reinforcing the complexity of translating these gains into meaningful improvements in everyday functioning. A multimodal, person-centered approach is needed to effectively translate cognitive improvements into meaningful real-world outcomes in people with schizophrenia.