Healthcare costs in patients with diabetes mellitus and comorbid mental disorders-a systematic review

Aims/hypothesis We systematically reviewed the impact of comorbid mental disorders on healthcare costs in persons with diabetes. Method We conducted a comprehensive search for studies investigating adult persons (>= 18 years old) with diabetes mellitus. All studies that allowed comparison of healthcare costs between diabetic patients with mental disorders and those without were included. Results We identified 4,273 potentially relevant articles from a comprehensive database search. Of these, 31 primary studies (39 publications) fulfilled inclusion criteria, of which 27 examined comorbid depression. Hospitalisation rates and hospitalisation costs, frequency and costs of outpatient visits, emergency department visits, medication costs and total healthcare costs were mainly increased with small to moderate effect sizes in patients with diabetes and comorbid mental disorders compared with diabetic patients without such problems. Frequency (standardised mean difference [SMD]=0.35-1.26) and costs (SMD=0.33-0.85) of mental health specialist visits were increased in the group with mental health comorbidity. Results regarding diabetes-related preventive services were inconsistent but point to a reduced utilisation rate in diabetic patients with comorbid mental disorders. Statistical heterogeneity between studies was high (I-2 range 64-98%). Pooled overall effects are therefore not reported. Studies included differ substantially regarding sample selection, assessment of diabetes and comorbid mental disorders, as well as in assessment of cost variables. Conclusions/interpretation In light of the increased healthcare costs and inadequate use of preventive services, comorbid mental disorders in patients with diabetes must become a major focus of diabetes healthcare and research.