Unraveling complex relationships among dysphoric disorder, localization-related epilepsy, and mood disorders

Dysphoric disorder (DD), characterized by intermittent pleomorphic symptoms, has been believed to be specific to epilepsy. However, our previous study revealed that DD in patients with localization-related epilepsy was associated with a lifetime diagnosis of mood disorders. The present study was conducted to estimate the prevalence of DD in patients with mood disorders, but not epilepsy, and to identify the clinical similarities and differences of DD in patients with either epilepsy or mood disorders.

Subjects consisted of 104 patients with localization-related epilepsy (group E) and 101 patients with DSM-IV mood disorders, but not with epilepsy (group M). After a diagnostic investigation for DD and the euthymic state, defined as the absence of any mood episodes during the last 12months, we compared the clinical characteristics of DD in patients from groups E and M.

Dysphoric disorder was apparently more common in group M (56.4%) than in group E (21.2%). However, 86.0% of patients in group M showed a temporal overlap between DD and the noneuthymic state, while 68.2% of patients in group E did not show this overlap. Moreover, the noneuthymic state was significantly associated with symptoms of DD, indicating that the diagnosis of DD was more likely to be overestimated when the subjects were in a noneuthymic state. The prevalence of DD, temporally independent of the noneuthymic state (pure DD), was estimated at 13.4% and 7.0% in groups E and M, respectively, and pure DD was 1.91 times more common in patients with epilepsy than in those with mood disorders. Diagnosis of pure DD was significantly associated with increased suicidality in group E, but not group M.

The present results suggest that DD is more familiar to epilepsy than mood disorders, although DD is not specific to epilepsy. Moreover, suicidality is specifically associated with DD in patients with epilepsy.