Neurocognitive dysfunctions in childhood-onset schizophrenia: A systematic review.

Objective: To conduct a systematic review of neurocognitive dysfunctions in patients with childhood-onset schizophrenia (COS), a neuropsychiatric disorder that occurs before age 13 and is rarer and more severe than adult-onset schizophrenia. Method: A search was made in the PubMed database. Sixty-seven studies (out of 543) which analyzed Intellectual Quotient (IQ), attentional, memory and executive functions were selected by two independent researchers. Study's appraisal was done according to the Mixed Methods Appraisal Tool (MMAT). This systematic review was registered on PROSPERO (CRD42024548945). Result: COS shows neurocognitive dysfunction in IQ with mean scores ranging from one to two standard deviation lower than normative data. Attentional deficits are observed with longer reaction time, more errors of omission and commission and slower processing speed than controls. In addition, working memory and executive functions, such as planification and flexibility are impaired. COS exhibit significantly more neurocognitive deficits than adolescent and adult-onset forms and display deterioration in intellectual functioning between premorbid period and after onset of psychosis. Conclusion: COS is characterized by major cognitive impairments, both before the onset of the disease and throughout its course. As in adult-onset schizophrenia, generalized cognitive impairment is found without the emergence of a specific profile, providing further support for the continuum hypothesis between early-onset and adult-onset schizophrenia. Collaborative research on a larger scale (including meta-analyses) and using complementary approaches (dimensional and multimodal) is needed to gain a better understanding of the cognitive impact of COS and pave the way for more precise and targeted cognitive remediation.