Biomarkers of epileptogenesis: psychiatric comorbidities (?)

The last decade has witnessed a significant shift on our understanding of the relationship between psychiatric disorders and epilepsy. While traditionally psychiatric disorders were considered as a complication of the underlying seizure disorder, new epidemiologic data, supported by clinical and experimental research, have suggested the existence of a bidirectional relation between the two types of conditions: not only are patients with epilepsy at greater risk of experiencing a psychiatric disorder, but patients with primary psychiatric disorders are at greater risk of developing epilepsy. Do these data suggest that some of the pathogenic mechanisms operant in psychiatric comorbidities play a role in epileptogenesis? The aim of this article is to review the epidemiologic data that demonstrate that primary psychiatric disorders are more frequent in people who develop epilepsy, before the onset of the seizure disorder than among controls. The next question looks at the available data of pathogenic mechanisms of primary mood disorders and their potential for facilitating the development and/or exacerbation in the severity of epileptic seizures. Finally, we review data derived from experimental studies in animal models of depression and epilepsy that support a potential role of pathogenic mechanisms of mood disorders in the development of epileptic seizures and epileptogenesis. The data presented in this article do not yet establish conclusive evidence of a pathogenic role of psychiatric comorbidities in epileptogenesis, but raise important research questions that need to be investigated in experimental, clinical, and population-based epidemiologic research studies.