People with a history of epilepsy are at increased risk of developing schizophrenia and schizophrenia-like psychosis, according to research published by the BMJ.
The study involved 2.27 million people who were born in Denmark between 1950 and 1987, whose personal and family histories of epilepsy and psychosis were obtained, and individuals were monitored for up to 25 years.
The researchers found that people with a history of epilepsy had nearly two and a half times the risk of developing schizophrenia and nearly three times the risk of developing a schizophrenia-like psychosis compared with the general population. The risk was the same for men and women but increased with age.
Both a family history of epilepsy and a family history of psychosis were also significant risk factors for schizophrenia and schizophrenia-like psychosis. The increased risk did not differ by type of epilepsy, but was significantly greater the older people were when they were first admitted to hospital for epilepsy.
The authors suggest that the two conditions may share common genetic or environmental causes:
'We think that this study is the first, on a population level, to show that a family history of epilepsy increases the risk of schizophrenia or schizophrenia-like psychosis even after adjusting for the effects of personal history of epilepsy and other factors.
'This finding suggests that genetic or environmental factors shared by family members may have an important role.'