Results: Background: To assess the relative frequency of schizophrenia diagnoses in those with and without diabetes.
Methods: Study subjects were a sample from 1997 to 2003 of all adults with prevalent diabetes (N=14,144) and their individually age and gender-matched non-diabetes control group (N=14,144). We classified those with one or more ICD-9 diagnostic codes for schizophrenia (ICD-9 codes 295, 297.9, 298.1, 298.3, 298.9) during a 24-month period as having a schizophrenia diagnosis.
Results: Among the adults with diabetes, 2.8% (N=399) had a schizophrenia diagnosis, while among age and gender-matched adults without diabetes, 1.5% (N=214) had a schizophrenia diagnosis (p= <.0001). Multivariate logistic regression models that controlled for patient age, gender, Charlson comorbidity score, and number of primary care visits, showed that adults with diabetes were significantly more likely than their age and gender-matched adults to have a schizophrenia diagnosis. The strength of the DM-schizophrenia relationship was weaker for patients with a modified Charlson score = 1 and for older patients.
Conclusion: Adults with diabetes appear to have a higher prevalence of schizophrenia than age and gender-matched adults without diabetes. There are several possible explanations of this finding. First, drugs used to treat either of these diseases (or their related conditions) may increase risk of the other disease. Second, these two diseases may have common genetic or environmental risk factors. These findings warrant further evaluation.