Contrary to the earlier findings, a new larger study has shown that instances of suicide among epileptics have nothing to do with the medications they consume and that underlying diseases are to be blamed for the behavior.

On an earlier occasion, a review of 199 samples by the United States Food and Drug Administration (FDA) found that patients taking the anti-epilepsy drugs showed about twice the risk of suicidal behaviour. Following these findings in 2008, the FDA required epilepsy medications to sport a label warning an increased risk of suicidal behaviours.

The new study conducted by researchers in Spain and the United States involving more than five million patients suggests that the increased risk of suicide has more to do with the conditions of the patients for which these drugs are prescribed than the medications themselves.

The investigators after evaluating the health records of primary care patients in England found that people with epilepsy, currently using antiepileptic drugs, are at no greater risk of suicide-related events than those who aren't taking the medications.

"In our opinion, in the long term, it is not the drugs themselves that raise the risk of suicide, but the underlying disease for which these drugs are prescribed," says study author Dr. Alejandro Arana, an epidemiologist and managing partner at Risk MR Pharmacovigilance Services, in Zaragoza, Spain.

According to him, treatment with antiepileptic drugs (AEDs) helps to control the psychiatric syndromes that are at the root of suicidal behavior in these patients.

To arrive at this conclusion, the researchers studied 5,130,795 patients who were seen in a general practitioner's office for at least six months between July 1988 and March 2008. After identifying the number of patients diagnosed with epilepsy, depression or bipolar disorder, they looked at how many people had received an antiepileptic medication that was included in the FDA's review and was also available in Britain.

The study focused on preparations like carbamazepine (Carbatrol, Equetro, Tegretol, Tegretol XR), gabapentin (Neurontin), lamotrigine (Lamictal), levetiracetam (Keppra), oxcarbazepine (Trileptal), pregabalin (Lyrica), tiagabine (Gabitril), topiramate (Topamax), valproate (Depakote, Depakote ER, Depakene) and zonisamide (Zonegran) prescribed to treat epilepsy patients.

The researchers followed up the participants for an average of six years. During the study period, 8,212 people attempted suicide, and 464 of these patients died as a result of their injuries.

An increased risk of suicide was found in two subgroups of patients taking these medications. They were people diagnosed with depression, and those who were prescribed an antiepileptic drug for a condition other than epilepsy, depression or bipolar disorder.

Patients who were prescribed an antiepileptic drug for a condition other than epilepsy were roughly two and a half times more likely to attempt or commit suicide than those who didn't take an antiepileptic medication, the say in the study published in the August 5 issue of the New England Journal of Medicine.

The reasons, however, for patients taking an antiepileptic medication even though they didn't have epilepsy, depression or bipolar disorder could not be ascertained. Chronic pain could be one reason associated with an increased risk of suicide.

The use of antiepileptic drugs in these patients is a marker of severe depression or the presence of another condition that may be associated with an increased risk of suicide-related events, the researchers say.