Was Michael Crichton right about a link between epilepsy and violence?The Terminal Man, a book published by Michael Crichton in the 1972, links explosive violence with epilepsy. This isn't the first book to put the two together — the idea that epileptic seizures could cause violence goes back into antiquity. But is there any truth to this notion?

Michael Crichton is best known for coming up with the story for the enduring cinematic powerhouse that is Jurassic Park, but he'd been writing stories for over a decade before it hit theaters. One of his earlier books (which was made into one of his earlier movies), was The Terminal Man. A man suffers a car accident that leaves him with brain damage and neurological episodes that spur him to near-superhuman violence. Doctors implant a chip in his brain that's meant to calm the episodes, and, since it's a thriller, everything goes wrong. For modern audiences, one of the most puzzling aspects of the entire book is the man's diagnosis - psychomotor epilepsy.

Today we don't think of epileptics as a dangerous bunch, but in the 1970s and 1980s, a diagnosis of epilepsy was employed in many a court case. And the twentieth century was not the first time this notion was explored. The idea of epileptic seizures as times of abnegation of responsibility dates back to when it was called "the falling sickness," and "the sacred disease." People who had epilepsy felt things, saw things, and behaved in ways that were alien to normal experience. These experiences were sometimes considered visions from gods, or possession by spirits. It made sense, then, that if a god could give a person a vision, a god could make that person harm another person, without the epileptic being responsible.

Courts in the 1970s didn't hold with possession by the gods, but they did consider the idea that epileptics could commit great violence against someone else during a seizure without being responsible. The idea was backed both by individual claims and by scientific study. In 1978 a man who murdered his wife with a hammer claimed that he did it during an epileptic seizure. After his arrest and jailing, he was observed having seizures and committing acts of violence during those seizures. One study, done in 1982, found that out of 97 incarcerated young men, 18 had epilepsy. Their level of violence correlated with the number of their psychomotor symptoms. People were — and sometimes still are — arrested for violent behavior, during or immediately after epileptic seizures. Psychomotor epilepsy also seemed like the best candidate for such violent behavior. It is confined to only parts of the brain, and so seizures don't generally look like the full body seizures that often happen when the entire brain is involved.

Was Michael Crichton right about a link between epilepsy and violence?

When people began taking a closer look, though, the tide began to turn. The man who had been incarcerated was observed during his seizures. It was true that he had no history of violence before the crime, and didn't display violent behavior outside of the seizures. Still, during his seizures, his violence was not directed. Although he struck out, he struck randomly and didn't follow up any strike with a continuing attack. This lack of direction was noted in other epileptics as well. A seizure isn't just a flipped switch that causes people to fall to the ground or become absent. It starts with a period of confusion in which people talk without meaning, become agitated, and sometimes fumble at their clothes. This can disturb people around them, who either approach or try to physically restrain them. As the intensity of the seizure increases, the epileptic strikes out. Epilepsy sufferers can also strike at people when they're coming out of a seizure. Often they lose awareness during the seizure and are alarmed when they come to and have someone touching them or standing close to them. Rarely, if ever, does any epileptic make any sort of directed and sustained attack.

As wider surveys were done, evidence began to pile up against the severity of epilepsy being associated with severity of violence in an epileptic. In 1986 a study of prison populations did show that epilepsy was more prevalent among prisoners than a wide control population, but epilepsy was also more prevalent among the lower socio-economic levels from which much of the prison population was drawn. Epilepsy was not more common among people who had committed violent crimes, and severe epilepsy did not seem to correlate with severe violence. The researchers concluded that violence as a result of epilepsy was extremely rare, and should only be considered as relevant if it was shown to be part of each epileptic event, not just the occasional shove by a confused person coming out of a seizure.

So is there a link between epilepsy and violent outbursts? In 1999, a study of fifty epileptics was done. Twenty-five had intermittent explosive disorder, or IED, which is characterized by sudden physical or verbal violence grossly out of proportion with the cause of such violence. In the twenty-five patients with IED, the researchers found atrophy of the amygdala and an increased rate of history of encephalitis. The amygdala processes both memory and emotion, helping us deal with things like confusion, anger, and fear. Encephalitis is brain inflammation, and has been shown to increase a risk of both IED and epilepsy. So a disease that increases the odds of epilepsy can also increase the odds of extreme violent outbursts, but that's hardly a correlation.

By the end of the 1980s, the epilepsy defense — and the idea that epilepsy might cause acts of violence — were both generally abandoned. In a post-script in a reprinting of The Terminal Man, Crichton himself wrote that any sort of violent behavior from epileptics was incredibly rare. Today, the link is almost forgotten, and so modern authors will have to find some other neurological bogeyman.

Via Epilepsy, Violence, and Aggression: Legal Implications, American Journal of Psychiatry, The Epilepsy Foundation, Epilepsia, Brain, Epilepsia, Medscape.