Fast track — ArticlesEpilepsy and risk of suicide: a population-based case–control study
Introduction
Individuals with epilepsy have a two to four times increased mortality compared with the general population.1 This excess mortality is only partly explained by causative factors such as brain tumours, stroke, or head trauma.2 Cohort studies from the UK3 and Sweden4, 5 have found a three to five times increased risk of suicide among individuals with epilepsy, but most studies were small.1, 4, 6, 7, 8, 9 A recent meta-analysis identified 29 studies, including 187 suicides, in people with a history of epilepsy.10 The US Department of Health and Human Services has concluded that there is insufficient evidence to suggest that patients with medically refractory epilepsy have an increased risk of suicide and have requested that cohort studies with sufficient size and follow-up should be done.11
There is a strong association between epilepsy and psychiatric disease,12 and psychiatric illness is one of the strongest risk factors for suicide.13 An increased risk of suicide among epilepsy patients with mental illness and use of antipsychotic drugs has been reported.4, 7, 9, 14, 15 However, no studies have been large enough to assess whether the risk of suicide is modified by history of psychiatric disease in patients with epilepsy.
Socioeconomic and demographic factors clearly play a part in the risk of suicide.15, 16, 17 Patients with epilepsy have lower quality of life and socioeconomic conditions compared with the general population, but whether these factors modify the risk of suicide in patients with epilepsy has yet to be studied.
We did a large population-based case–control study of the association between epilepsy and suicide, and took psychiatric disease, and demographic and socioeconomic factors into account.
Section snippets
Data sources
Epilepsy, psychiatric, socioeconomic, and demographic data were retrieved and merged from five nationwide longitudinal registries in Denmark: the Danish National Hospital Register, the Cause of Death Register, the Danish Psychiatric Central Register, the Danish Integrated Database for Labour Market Research (IDA database), and the Danish Civil Registration System.
The Danish National Hospital Register provided information on epilepsy for hospital inpatients (1980–1997) and outpatients
Results
We identified 21 169 suicide cases and 423 128 controls. Among individuals who committed suicide, 492 (2·32%) had a history of epilepsy compared with 3140 (0·74%) controls. People with epilepsy had a three times higher risk of suicide (RR 3·17 [95% CI 2·88–3·50]; p<0·0001) compared with people with no such history. The risk of suicide in the general population is known to increase with age,25 but the increase was not as strong among patients with epilepsy (0·985, 0·980–0·991; p<0·0001). From
Discussion
In this population-based study, we identified a more than three times higher risk of suicide among people with a diagnosis of epilepsy. Our results are in keeping with those of some previous studies,1, 3, 4, 5 but not all.27, 28
The major strengths of this study are the size, the population-based nature, the minor loss to follow up, and the opportunity to adjust for comorbid psychiatric disease and underlying demographic and socioeconomic factors. The most important confounding factor for the
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