A history of epilepsy more than doubles the risk of developing schizophrenia or schizophrenia-like psychosis, according to findings from a population-based study appearing in the British Medical Journal.

Numerous reports have linked epilepsy with schizophrenia, but there has been limited data from large-scale studies, Dr. Ping Qin, from the University of Aarhus in Denmark, and colleagues note.

In their study, the researchers assessed the link between the two disorders by analyzing data from 2.27 million people who were born in Denmark between 1950 and 1987.

A history of epilepsy raised the risk of schizophrenia and schizophrenia-like psychosis by 2.48- and 2.93-fold, respectively, the authors report.

The impact of epilepsy on schizophrenia risk was the same for men and women, and it increased with age. The type of epilepsy did not make a difference, but the risk of schizophrenia was strongest in subjects lacking a family history of psychosis.

An increasing number of hospital admissions for epilepsy, and epilepsy onset later in life, were particularly strong risk factors for schizophrenia.

“To our knowledge, this is the first population based study on epilepsy and schizophrenia-like psychosis that has taken the family history of psychosis and epilepsy into consideration and examined the interactions between these factors,” the authors note.

The findings, they add, “corroborate previous results indicating a strong link between these two conditions.”

SOURCE: British Medical Journal, online June 17, 2005.