Abstract
Objective: To carry out a systematic review of the literature addressing cognitive functions in first-episode psychosis (FEP), divided into domains. Although this is not a full “cognitive-genetics-in-schizophrenia review,” we will also include putative ideas of mechanism(s) behind these impairments, focusing on how early stress, and genetic vulnerability may moderate cognitive function in psychosis.Method: Relevant studies were identified via computer literature searches for research published up to and including January 2013, only case-control studies were included for the neurocognitive meta-analysis.Results: Patients with FEP present global cognitive impairment compared to healthy controls. The largest effect size was observed for verbal memory (Cohen’s d effect size = 2.10), followed by executive function (effect size = 1.86), and general IQ (effect size = 1.71). However, effect sizes varied between studies.Conclusion: Cognitive impairment across domains, up to severe level based on Cohen’s effect size, is present already in FEP studies. However, differences in levels of impairment are observed between studies, as well as within domains, indicating that further consolidation of cognitive impairment over the course of illness may be present. Cognitive abnormalities may be linked to a neurodevelopmental model including increased sensitivity to the negative effect of stress, as well as genetic vulnerability. More research on this field is needed.
Highlights
With an increased awareness of the extent of cognitive impairments present in schizophrenia, cognitive dysfunction is viewed by many as a core abnormality of the disorder (1, 2)
Patients with first-episode psychosis (FEP) present global cognitive impairment compared to healthy controls.The largest effect size was observed for verbal memory (Cohen’s d effect size = 2.10), followed by executive function, and general IQ
GENERAL INTELLECTUAL FUNCTION Overall, patients with FEP scored significantly worse on current IQ assessed by the Wechsler Adult Intelligence scale (WAIS) battery compared to controls
Summary
With an increased awareness of the extent of cognitive impairments present in schizophrenia, cognitive dysfunction is viewed by many as a core abnormality of the disorder (1, 2). The majority of patients with schizophrenia function at a cognitive level of at least one standard deviation below that of healthy comparison groups (3, 4). Together with a global impairment in cognitive function, specific domains show greater dysfunction, such as episodic memory, working memory, and executive function (5, 6). There are patients with schizophrenia with cognitive scores in the normal or above-normal range, varying in different studies from 15 to 45% (6–10). In the high cognitive function subgroup, 64% still have abnormal scores on at least one cognitive domain, compared to 35% of healthy controls (7). Most of the high functional group demonstrates some kind of cognitive deficit compared to healthy controls
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