Studies of people with schizophrenia have found a link between the condition and type 2 (adult-onset) diabetes. This could be due to the effect of schizophrenia itself, common genes which could lead to a vulnerability to developing schizophrenia and type 2 diabetes, the effects of antipsychotic medication, the unhealthy lifestyles of people with schizophrenia and the weight gain often associated with antipsychotic drugs. However, there have been very few studies into the links between schizophrenia and type 1 (childhood-onset) diabetes. A study of 5,009 people with type 1 diabetes in Finland has found that they were actually at less than half the risk of developing schizophrenia as people without diabetes.
Juvonen, Hannu ... [et al] - Incidence of schizophrenia in a nationwide cohort of patients with type 1 diabetes mellitus Archives of General Psychiatry 2007, 64(8), 894-899