A Systematic Review of Cognitive Function in First-Episode Psychosis, Including a Discussion on Childhood Trauma, Stress, and Inflammation

Aas, Monica; Dazzan, Paola; Mondelli, Valeria; Melle, Ingrid; Murray, Robin; Pariante, Carmine M. · 2014 · OpenAlex-citations

DOI: 10.3389/fpsyt.2013.00182

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Summary

This systematic review investigates cognitive function in patients experiencing first-episode psychosis (FEP), aiming to characterize the extent and nature of cognitive impairments at illness onset. The study was motivated by the need to distinguish neurodevelopmental deficits inherent to psychosis from those potentially caused by chronic illness duration or long-term pharmacological treatment. By focusing on FEP, the authors sought to identify cognitive profiles that reflect the underlying neurodysfunction of the disorder. Additionally, the review explores putative mechanisms behind these impairments, specifically examining the roles of childhood trauma, stress sensitivity, and genetic vulnerability. The authors conducted a systematic search of Medline (PubMed) and PsycINFO databases for case-control studies published up to January 2013. Twenty-four articles meeting inclusion criteria were analyzed. The study calculated Cohen’s d effect sizes to quantify the magnitude of cognitive differences between FEP patients and healthy controls from the same catchment areas. This approach allowed for a detailed comparison across specific cognitive domains, including general intellectual function, executive function, attention, working memory, verbal and non-verbal memory, processing speed, and motor speed. The review included all types of FEP, not limited to schizophrenia, to account for diagnostic heterogeneity in early stages. The results indicate that patients with FEP exhibit significant global cognitive impairment compared to healthy controls, with effect sizes exceeding 0.8 in all investigated domains. The most severe deficits were observed in verbal memory, with a maximum Cohen’s d of 2.10, followed by executive function (1.86) and general IQ (1.71). Specific impairments were noted in verbal declarative episodic memory, executive tasks such as the Wisconsin Card Sorting Test, and working memory. While schizophrenia patients generally showed greater cognitive deficits than those with affective psychosis, there was considerable variation in effect sizes across studies. Pre-morbid IQ estimates also revealed significant differences between patients and controls, suggesting that cognitive abnormalities may precede or coincide with the onset of psychotic symptoms. The authors conclude that cognitive impairment is a core feature of psychosis present at the first episode, supporting a neurodevelopmental model of the disorder. The findings suggest that these deficits are linked to increased sensitivity to stress and gene-environment interactions. The review highlights that cognitive abnormalities are not solely a consequence of chronic illness or treatment but are intrinsic to the early stages of psychosis. The authors emphasize the need for further research to consolidate understanding of how cognitive impairment evolves over the course of the illness and to elucidate the specific environmental and genetic factors contributing to these deficits.

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• cognitive capacity variation