A large study from Denmark has found that people who have epilepsy are three times more likely to commit suicide than the average person. The risk is higher if they have been diagnosed with epilepsy within the last six months, and higher still if they also have a psychiatric condition, such as depression, bipolar disorder (manic depression), schizophrenia, chronic alcohol use, or anxiety, among others. The results confirm that there is more to epilepsy than just treating seizures.

This is the biggest study carried out on epilepsy and suicide risk to date. Analysing data from nearly half a million people in total allowed Dr Jakob Christensen and colleagues from Aarhus University Hospital, Denmark, to distinguish between the effect of epilepsy itself on suicide rate and the effects of other factors. For example, people with epilepsy are more likely to have a psychiatric condition (see the list above) than the general population, and people who have psychiatric conditions are more likely than average to commit suicide. So is the high rate of suicide among people with epilepsy due to the high rate of psychiatric conditions in this group, or to their epilepsy? In this study, the effects of age, sex, family background, marital status, employment, amount of sick leave from work, and income level on suicide rate were also investigated.

The researchers analysed data from 21,169 people who committed suicide between 1981 and 1997 in Denmark. They matched each suicide case with 20 control cases, that is people in the general population of the same age and sex, who had not committed suicide.

Only 0.74% of the control cases had a diagnosis of epilepsy, compared with 2.32% of the people who committed suicide; this is three times as many. People who had both epilepsy and a psychiatric condition were nearly 14 times more likely to commit suicide than the average.

Whether the epilepsy was recently diagnosed or not also made a big difference: people who had been diagnosed with epilepsy in the last six months were five times more likely than the average person to commit suicide; people who had both a psychiatric condition and a new diagnosis of epilepsy were 29 times more likely to commit suicide than the average. This may be due to the fact that new cases of epilepsy are more likely to be experiencing regular seizures; six months after diagnosis, treatment will have reduced seizure frequency in some people.

The association between epilepsy and suicide was stronger for women than for men. Suicide rates were higher for younger people than for older people with epilepsy; this is the opposite of what's seen in the general population, where older people are more likely to commit suicide.

The results of this study, which will be published in the August issue of Lancet Neurology, are important because they establish that having epilepsy itself can increase the likelihood of suicide, not just when occurring with a psychiatric condition. Doctors should be prepared to counsel all people newly diagnosed with epilepsy about this. They should be especially careful with people who also have a psychiatric diagnosis.

Suicide rates in Denmark are higher than in the UK (see data from the World Health Organisation). Suicide rates vary widely between countries, and appear to depend on a number of economic, climatic, social and cultural factors. The rates for specific age groups may also vary between countries; they may also do so for health groups. Previous studies in the UK have however also found increased rates of suicide among people with epilepsy.

On a positive note, Dr Christensen and his colleagues found that the rate of suicide among people with epilepsy fell over the years covered by the study. They attributed this to the use of newer anti-epileptic drugs which have fewer side effects, the reduced use of some older types of anti-epileptic drugs, and improvements in epilepsy care.

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