Depressive symptoms in epilepsy: prevalence, impact, aetiology, biological correlates and effect of treatment with antiepileptic drugs.

Occurring in up to 80% of patients with epilepsy, depression in epilepsy may manifest as (i) major depressive disorder, meeting Diagnostic and Statistical Manual, 4th edition (DSM-IV) diagnostic criteria; (ii) atypical depression or dysthymia; or (iii) a dysthymic-like disorder with intermittent symptoms that can be milder than those of major depression. Depressive symptoms impair patients' health-related quality of life and may affect the clinical course of epilepsy. Depressive symptoms in epilepsy have been attributed to several causes, including endocrine and/or metabolic effects of seizures; the psychological response to epilepsy and its associated mental, physical and social challenges; common pathogenic mechanisms between depression and epilepsy; and the adverse effects of certain antiepileptic drugs (AEDs), particularly GABAergic agents, such as vigabatrin, tiagabine, topiramate and phenobarbital. Whereas some AEDs impair mood, others appear to improve aspects of mood or are mood neutral. Demonstrable antidepressant efficacy of AEDs used to manage seizures could have a significant impact on the care of patients with epilepsy. The AED lamotrigine has been demonstrated to be effective in the treatment of depressive symptoms in patients with epilepsy. In randomized, double-blind, clinical trials in patients with epilepsy, depressive symptoms improved more with lamotrigine monotherapy than valproate monotherapy and more with lamotrigine adjunctive therapy than placebo. Results of open-label studies of lamotrigine monotherapy and adjunctive therapy are consistent with the results of double-blind clinical trials. Lamotrigine-associated improvement in depressive symptoms is independent of its anticonvulsant efficacy. In prospective assessments, gabapentin, levetiracetam and oxcarbazepine each exhibited potentially beneficial effects on depressive symptoms in patients with epilepsy. However, evidence for the efficacy of gabapentin, levetiracetam and oxcarbazepine in the treatment of depressive symptoms in epilepsy is inconclusive at present because the effects of each agent have only been reported in single studies of an open-label design and with small sample sizes.