But the cause is unclear about two-thirds of the time, he said. However, "in the last 15 years, there's been a concerted effort to try to get to the bottom of the majority of these." Genetics appear to play. In the United States, an estimated three million people have the disorder. -- Researchers have linked a genetic variation to a com form of epilepsy in children, potentially paving the way toward greater insight into the disorder.

In some cases, the cause of epilepsy is obvious, Pal said. The condition causes seizures when electrical signals in the brain are disrupted. It may develop after a head injury or brain tumor, for instance. Epilepsy affects an estimated 60 million people worldwide, about 1 percent of the entire population, Pal said. "It's the first step toward developing a diagnostic test, which can help provide a more precise diagnosis and information about which particular drug or treatment may be effective," said study senior Deb Pal, a pediatric neurologist and research scientist at Columbia University.

In the worst cases, the seizures rob people of consciousness and control over their bodies.