Researchers have found that depression appears to increase the risk for epilepsy and worse seizure outcomes, implying that shared underlying pathophysiological mechanisms may explain the risk of developing epilepsy after depression.

Colin B. Josephson, MD, from the University of Calgary in Alberta, Canada, and colleagues identified 10,595,709 patients in The Health Improvement Network and calculated the risk of developing either epilepsy after incident depression or depression after epilepsy.

Of these patients, 229,164 (2.2%) developed depression, and 97,177 (0.9%) developed epilepsy. The median ages of those with depression and epilepsy was 44 years (range, 32-58 years) and 56 years (range, 43-71 years), respectively. There were significantly more women with depression than men (144,373 [63%] women vs 84,791 [37%] men; P <.001). Of those with epilepsy, 54,419 (56%) were women and 42,758 (44%) were men (P <.001).

The researchers found that among those with depression, patients receiving counseling alone had the lowest risk for epilepsy (hazard ratio [HR], 1.84; 95% CI, 1.30-2.59; P <.001). Those receiving antidepressants alone had an intermediate risk for epilepsy (HR, 3.43; 95% CI, 3.37-3.47; P <.001), and those receiving both counseling and antidepressants had the highest risk for epilepsy (HR, 9.85; 95% CI, 5.74-16.90; P <.001). The researchers used depression treatment as a representation of how severe patients’ depression was, implying that those with worse depression were at a higher risk for epilepsy.

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Depression also affected the relationship between epilepsy and sex, social deprivation, and Charlson Comorbidity Index (CCI), accounting for 4.6%, 7.1%, and 20.6% of the total effects of these variables, respectively.

The chances of achieving 1 year without seizures was significantly lower for those with depression or treated depression compared with those without depression.

“Our study adds to the existing knowledge by demonstrating a temporal association and an apparent severity gradient in the association between depression and epilepsy,” the researchers concluded.

“Furthermore, we provide novel evidence that depression partially mediates the effects of sex, socioeconomic deprivation, and [Charlson

Comorbidity Index] on the risk of developing epilepsy,” the authors wrote. This suggests that interventions focusing on depression may reduce the effect of these variables on epilepsy, they said.

Reference

Josephson CB, Lowerison, Vallerand I, et al. Association of depression and treated depression with epilepsy and seizure outcomes: a multicohort analysis [published online February 27, 2017]. JAMA Neurol. doi: 10.1001/jamaneurol.2016.5042