Study Links Epilepsy and Schizophrenia Risk
But an Expert Calls the Risk 'Fairly Low'
The Danish study was based on records in a national database of more than 2.2 million people age 15 and older. Researchers reviewed their histories until December 2002, or until they died or were diagnosed with schizophrenia or schizophrenia-like psychosis.
Very few people (1.5%) had epilepsy and only a sliver of them had schizophrenia or related psychosis. Of the epilepsy patients, fewer than one in a hundred (0.8%) were admitted to a hospital for schizophrenia, and 1.5% were admitted for schizophrenia-like psychosis.
The risk was similar for men and women, and for all types of epilepsy. Age and family history of epilepsy or schizophrenia were important. The risk rose with age and was higher in those with no family history of psychosis.
Hospital treatment is free for all Danish residents, so economic factors shouldn't have interfered, say the researchers. They included Ping Qin, an associate professor at Denmark's University of Aarhus.
Raison says he's not surprised to see an increase in schizophrenia among epilepsy patients. "It had been part of our medical lore that some percentage of people with epilepsy would slowly, over time, develop chronic psychotic conditions," he says. There has been debate about when to call those problems schizophrenia, says Raison.
Again, those are the exceptions, not the rule. A small percentage of epilepsy patients experience psychotic symptoms during or after seizures. Those problems more often follow in the days or weeks after a seizure, and sometimes get resolved without developing into chronic conditions, says Raison.
However, it's more common for seizures to be accompanied by depression or anxiety, he says. Of course, those problems aren't universal among epilepsy patients.
The findings "probably reflect an underlying link, physiologically, that we haven't figured out yet," says Raison. There may be "abnormalities in the ways neurons are wired together." Those problems may develop early in life and manifest later on, usually in early adulthood.
Future studies may address whether schizophrenia risk is higher for epilepsy patients who experience psychosis during or after seizures, he says.