Schizophrenia is a lifelong mental disorder associated with cognitive dysfunctions.
Comorbid metabolic dysregulations, such as diabetes and insulin resistance, may further
deteriorate cognitive functions. It is therefore essential to investigate the effects
of these metabolic disturbances on cognition in this population. A systematic review
and meta-analysis following PRISMA guidelines was conducted using data from five databases:
Medline, Embase, CENTRAL, Scopus, and Web of science. Of the 26 studies included,
9 were meta-analyzed with random effects model. The search was completed on November
23, 2023 and updated on April 2, 2025. We examined the cognitive functions of schizophrenia
patients with and without diabetes or insulin resistance, using standardized mean
differences (SMD) or mean differences (MD) as outcomes. The review section provides
an overview of the literature on the relationship between glucose homeostasis and
cognitive functions. The risk of bias was assessed using the QUIPS tool. There is
a clear trend suggesting that diabetes exacerbates cognitive dysfunction in schizophrenia
(global cognition: SMD=-0.26; P = 0.1087; 95% CI, -0.59 to 0.08), particularly in
domains such as reasoning (SMD=-0.40; P = 0.0109, 95% CI -0.58 to -0.22) and processing
speed (SMD=-0.43; P = 0.0005, 95% CI -0.52 to -0.35). Conflicting results were observed
in studies on insulin resistance (global cognition: SMD=-0.12; P = 0.5890; 95% CI
-0.91 to 0.68). Our findings suggest that glucose metabolism dysregulations might
worsen cognitive dysfunctions in schizophrenia. However, further research is needed
with larger samples and less heterogeneous studies to investigate if the effect is
statistically significant. Addressing these metabolic issues could help improve cognitive
and functional outcomes in schizophrenia patients.
