The comorbidity of epilepsy and mood disorders has been a subject of interest and of many studies for decades. Although the data on the prevalence of bipolar disorder in epilepsy is still limited, there is growing evidence that these disorders are frequently comorbid. Bipolar disorder and epilepsy have a number of clinical, biochemical and pathophysiological features in common.
Mood disorders in epilepsy often have atypical symptomatology and fail to meet DSM-IV-TR criteria. They can be classified according to the temporal relationship between the onset of psychiatric symptoms and seizure occurrence into ictal (as a clinical manifestation of the seizure), peri-ictal (symptoms precede [pre-ictal] and/or follow [postictal] the seizure), and interictal (symptoms occur independently of the seizure occurrence).
A pleomorphic affective syndrome in patients with epilepsy has been named interictal dysphoric disorder (IDD). Recent data suggest that some symptoms of IDD can be related rather to bipolar spectrum disorder than to unipolar depression, which has implications for treatment and prognosis.
Keywords: epilepsy, bipolar disorder, interictal dysphoric disorder, kindling