Schizophrenia risk may be lower in type 1 diabetics
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The incidence of schizophrenia in patients with type 1 diabetes is less than half of that seen in people without diabetes, according to findings published in the Archives of General Psychiatry.
“Patients with schizophrenia have an increased risk of type 2 diabetes mellitus,” Dr. Hannu Juvonen and colleagues from the National Public Health Institute, Helsinki, point out. However, no conclusive studies have examined the relationship between schizophrenia and type 1 diabetes.
Type 1 and type 2 diabetes are two distinct conditions. Type 1 diabetes, which is usually detected early in life, occurs when insulin-producing cells in the pancreas are damaged, usually by a faulty immune reaction. Thus, condition is considered to be an autoimmune disease.
Type 2 diabetes, usually diagnosed in middle age, occurs when the body becomes less responsive to insulin, leading to high blood sugar levels. A major risk factor for Type 2 diabetes is being overweight or obese.
The researchers examined the incidence of schizophrenia in a nationwide study of 896,175 people. The subjects were born between 1950 and1959 in Finland, and were followed from 1969 to 1991. A total of 5009 patients had type 1 diabetes.
Juvonen’s team found that schizophrenia was diagnosed less than half as often in the subjects with type 1 diabetes compared with those without type 1 diabetes, and this difference was statistically significant.
The origins of schizophrenia and type 1 diabetes have some common features - both are “highly inheritable” diseases. There is also evidence that prenatal or childhood infections and seasonal birth patterns may be involved in both conditions.
Furthermore, the results of previous studies appear to contradict the findings of the current study - suggesting a possible link between type 1 diabetes and an increased risk of schizophrenia. Another study found an excess risk of diabetes type 1 among the close relatives of schizophrenics.
The investigators recommend more studies of families with schizophrenia and type 1 diabetes to examine the possibility of a genetic, immunologic or infectious role in these two diseases.
SOURCE: Archives of General Psychiatry, August 2007.
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