The prevalence of metabolic syndrome in people with severe mental illness: a mediation analysis

BACKGROUND: People with severe mental illness (SMI) generally have high rates of metabolic syndrome (MetS). Proposed explanations remain conjectural. Relatively little is known about Mets in SMI in Southern Europe, an area with generally healthy dietary traditions. PURPOSE: To establish prevalence rates of MetS in an Italian sample, and testing hypotheses about putative reasons for the excess in the SMI group. METHODS: We compared the prevalence and correlates of MetS in inpatients with SMI and controls randomly chosen from patients undergoing routine maxillofacial surgery. We employed formal tests of mediation. RESULTS: The MetS prevalence rate was 26.1 % in the SMI group and 15.9 % in the comparison group. After controlling for age, people with SMI were three times more likely to have MetS than their non-SMI counterparts. Smoking and a family history of cardiovascular disease were strongly related to MetS in both groups. However, these factors could not explain the excess of MetS in the SMI group, and we found no effect of antipsychotic dose. CONCLUSIONS: SMI remained prominent in increasing the likelihood of MetS in this low prevalence population, and putative determinants of MetS were common to people with SMI and to controls. Explanations for high MetS rates in SMI may lie in health behaviours other than smoking.