Researchers at Columbia University and the University of Reykjavik,
Iceland, have identified a potential link between depression, suicide, and
epilepsy. Epilepsy, they believe, is linked to both depression and suicide,
but the link is probably through different brain mechanisms. Surprisingly,
however, they found no statistically significant link between suicide and
The report, supported by the National Institute of Neurological Disorders
and Stroke, was published online in advance of print in the "Early
View" section of the Annals of Neurology.
"For reasons that are not understood, depression both increases the
risk for developing epilepsy and is also common among people with epilepsy who
experience many seizures," said lead author Dale Hesdorffer, Ph.D., in a
press release. Hesdorffer is an assistant professor of epidemiology at the
Gertrude Sergievsky Center at Columbia University.
The report noted that "it has commonly been assumed that the
difficulties associated with living with epilepsy could provoke depression
and, in some cases, an increased risk of suicide. But it is harder to explain
the opposite finding—that people who develop depression have a higher
risk of later experiencing a first seizure."
Over the last decade, neuroscientists have hypothesized that depression and
epilepsy may involve overlapping brain systems, but evidence for a dual
mechanism is preliminary. Hesdorffer and his colleagues hoped to define more
clearly the relationship between depression, suicide, and epilepsy.
"One question we had was whether some symptoms of depression were
more important than others for increasing the risk for developing
epilepsy," said Hesdorffer. "Suicidal thoughts and suicide attempt
were possibilities, because people with epilepsy seem to be more likely to
commit suicide than the general population. But we looked at all symptoms of
Hesdorffer and colleagues undertook a population-based case-control study
of 324 Icelandic children and adults (aged 10 and over) who had a new
diagnosis of unprovoked seizures or epilepsy between December 1, 1995, and
February 28, 1999, and 647 control subjects without epilepsy.
The researchers expectedly found that a history of depression increased the
risk of epilepsy (odds ratio 1.7 compared with controls). However, the team
was surprised to find that people with epilepsy were 3.9 times more likely
than controls to have attempted suicide before ever having a seizure. The
elevated risk remained strong (odds ratio 3.5 compared with controls) even
after other factors were taken into account like alcohol consumption, history
of depression, age, and gender.
The individual presence of symptoms that did not meet threshold criteria
for major depressive disorder did not predict a greater likelihood of later
development of seizures.
Those with a history of depression and a previous suicide attempt were 13.3
times more likely than controls to develop seizures. Subjects with a history
of suicide attempt but not depression were 4.2 times more likely than controls
to develop seizures. Subjects with a history of depression but not suicide
attempt were 1.5 times more likely to develop seizures in the future; however,
this finding did not reach statistical significance.
The researchers reported that the results suggest common underlying brain
mechanisms for suicidal behavior and epilepsy. Yet, they added, the results
also suggest that depression and suicidal behavior may be related to different
"Increasingly, clinicians treating people with epilepsy ask about
current depression, but they may not ask about past suicide attempt or
suicidal thoughts," said Hesdorffer. "Our results may alert
clinicians to the need to ask this question and offer any needed counseling to
prevent the occurrence of later completed suicide."
"We plan to follow up with studies designed to see whether the
co-occurrence of these disorders is explained by shared genetic susceptibility
and with studies that examine possible common underlying neurotransmitter
abnormalities," said Hesdorffer.
An abstract of "Depression and Suicide Attempt as Risk Factors
for Incident Unprovoked Seizures" is posted at<www3.interscience.wiley.com/cgi-bin/abstract/112100865/ABSTRACT>.▪