Prediabetic markers, particularly impaired glucose tolerance and insulin resistance, are potentially linked with first-episode psychosis, according to a systematic review and meta-analysis published in Lancet Psychiatry.1
A team of researchers based in Warwick, Coventry, UK, searched several databases for clinical studies published between database inception and January 6, 2016. They analyzed case-controlled studies that included biochemical assessment of prediabetic status in patients with first-episode psychosis, alongside matched controls. Measurements for prediabetes included fasting plasma glucose, insulin resistance (measured by the Homeostatic Model Assessment) and impaired glucose tolerance. The researchers calculated standardized mean differences for each outcome.
Twelve studies (n= 1137 participants) were included in the final analysis. Pooled analyses found first-episode psychosis to be related to insulin resistance (mean difference 0∙30 [95% CI 0∙18 to 0∙42]), impaired glucose tolerance (mean difference 1∙31 [0∙37 to 2∙25]), and the number of patients with impaired glucose tolerance (odds ratio 5∙44 [2∙63 to 11∙27]), but not fasting plasma glucose (mean difference 0∙03 mmol/L [–0∙04 to 0∙09]).
The study was inspired by the observation that schizophrenia might share intrinsic inflammatory disease pathways with type 2 diabetes. The researchers hypothesized that “biochemical measures of prediabetic states would be more common in antipsychotic naïve patients with first-episode psychosis than in healthy controls.”The research corroborated this hypothesis. ‘The glycemic abnormalities associated with first-episode psychosis might be intrinsic and extend beyond the known effects of medication, lifestyle, and access to healthcare,” the researchers wrote. . First-episode psychosis might be regarded as “a developing schizophrenia,” just as prediabetes is “a developing diabetes,” suggesting that the “two disorders develop in unison.” The “intrinsic disease links” shared by schizophrenia and type 2 diabetes “might be inflammatory in nature.”
Nevertheless, the researchers cautioned that their study “cannot establish causality, and the studies contributing to this review were at some risk of bias.”
On the other hand, the findings “might help to explain the increased prevalence of type 2 diabetes in patients with schizophrenia, and could have implications for the management of patients with schizophrenia,” they noted.
The researchers cautioned that if patients are at an increased risk of developing glycemic regulation abnormalities, even before the administration of antipsychotics, “heightened vigilance and stricter control of the metabolic indices of patients with schizophrenia is essential to help reduce the physical health burden associated with the disease.”
Perry BI, McIntosh G, Welsh S, et al. The association between first-episode psychosis and abnormal glycemic control: systematic review and meta-analysis. Lancet Psychiatry. 2016; 11:1049-1058.