It has long been recognized that depression is common among people with epilepsy. "The assumption has been that having epilepsy increases the risk of depression and, in a subgroup, completed suicide," the authors write.
But the new research hints that suicidal behavior is a specific threat in people with epilepsy even before the disease is diagnosed. "The relationship between depression and unprovoked seizures is much more complex than previously appreciated," researchers add.
Researchers examined a history of depression and suicidal behavior among people who were diagnosed with an unprovoked seizure and who later developed seizures associated with epilepsy.
Children and adults with unprovoked seizures were more likely to have suffered from major depression before unprovoked seizure than people in the general population. They show that the higher the number of depressive symptoms the greater the risk of unprovoked seizures.
However, the researchers also show that children and adults with unprovoked seizures were four times as likely to have attempted suicide compared with those in the general population.
"This tells us that there is probably a common underlying brain dysfunction that links epilepsy and suicidal behavior," researcher Dale C. Hesdorffer, PhD, tells WebMD.
Seizures Don't Explain Depression
Roughly 2.7 million Americans have epilepsy or other seizure disorders, and 200,000 new cases are diagnosed each year.
Depression has been shown to be at least three times more common among people with epilepsy than among the general population. It is clear that the difficulties of living with seizures can cause depression, but this does not appear to fully explain the link.
For example, people with a history of depression have been shown to have a higher risk of developing epilepsy. And studies have failed to show a link between the length and severity of seizures and depressive symptoms.
In an effort to clarify the relationship between depression, suicide, and epilepsy, Columbia University researchers compared people with unprovoked seizures with those without the condition who were enrolled in a health registry in Iceland.
Among the symptoms associated with depression, only suicidal attempts were shown to be a risk factor for developing unprovoked seizures. The association remained strong after other suicide risk factors were considered.
The study is published in the November issue of the journal Annals of Neurology.
Hesdorffer says the findings have implication for the management of patients who have recently been diagnosed with epilepsy.
"Increasingly, clinicians treating people with epilepsy ask about current depression, but they may not ask about past suicide attempts or suicidal thoughts," Hesdorffer says. "Our results may alert clinicians to the need to ask this question and offer any needed counseling to prevent [later] suicide."
The findings may also help explain why the suicide rate among epileptics is so high.
In April, the FDA asked more than a dozen pharmaceutical companies to reexamine their study data involving seizure medications to determine if these drugs could be linked to suicidal thoughts or behaviors.
Hermann is chair elect of the Epilepsy Foundation's professional advisory board, and he is also a neurology professor at the University of Wisconsin.
"Clearly some people get depressed because they are living with a chronic disease, but depression could also be an early sign that something is not right within the brain," he says.
He agrees that physicians need to evaluate their epileptic patients for depression. According to one study, more than half of patients with both disorders never get treated for depression.
"If it is true that mood disorders and these other problems occur before or close in time to when the epilepsy starts, it is important to look for these symptoms and treat them," he says.