On the increased risk of developing late-onset epilepsy for patients with major affective disorder

Background: Based on register data we wanted to investigate whether patients with a diagnosis of affective disorder are at increased risk of developing epilepsy compared to other medically ill control groups. Methods: By linkage of public hospital registers covering the whole of Denmark from 1977 to 1993, using ICD-8 diagnoses, three study cohorts were identified: Patients with first affective disorder episodes (mania and depression), patients with first osteoarthritis and patients with first diabetes discharge. Time to first diagnosis of epilepsy was estimated with the use of survival analysis. Results: A total of 164,227 patients entered the study base: 13,748 patients with mania or depression, 81,380 patients with osteoarthritis and 69,149 patients with diabetes. The risk of getting a diagnosis of epilepsy was increased for patients with affective disorder compared with the risk for the control groups. However, the increased risk seemed to be due to the effect of comorbid alcohol or drug abuse and not to the effect of the affective illness itself. Limitations: The results only apply to hospitalised patients. Diagnoses are not validated for research purposes. Conclusion: Patients with a diagnosis of affective disorder have an increased risk of developing epilepsy in later life. In patients with affective disorder, comorbid alcoholism/drug abuse seriously increased the risk of a subsequent diagnosis of epilepsy.