Adherence to Diabetes Medication in Individuals with Schizophrenia: A Systematic Review of Rates and Determinants of Adherence.

Introduction: Despite the importance of medication adherence for the effective treatment of type II diabetes mellitus (T2DM), little research has examined adherence with diabetes medication treatment in schizophrenia. The purpose of this systematic review was to: 1) evaluate rates of adherence and determinants of adherence with medication for T2DM in individuals with schizophrenia; and, where possible, 2) examine the relationship between medication adherence and glycemic control.

Methods: Studies were included if they presented information on dosing regimens and adherence or compliance rates for T2DM and included samples where at least 50% of the participants were individuals with schizophrenia.

Results: Six studies were included in this review that predominantly examined men over the age of 50 years. Studies confirmed that many individuals with schizophrenia were not adhering to their diabetes medication as adherence rates ranged from 51-85%. Two studies that compared medication adherence in individuals with and without schizophrenia found those with the mental illness had higher rates of adherence. One study reported that blood glucose control levels were not statistically different between those who did and did not adhere to their medication, indicating more research is necessary in this area. Factors that improved adherence included disease and medical service and medication-related factors.

Conclusions: Interventions to increase diabetes medication adherence in schizophrenia need to address disease and medical service and medication-related factors. Further research needs to examine diabetes medication adherence in women, younger individuals, and those recently diagnosed with diabetes as these individuals have been underrepresented in the literature.