Interictal dysphoric disorder in patients with localization-related epilepsy: Diagnostic relationships with DSM-IV psychiatric disorders and the impact of psychosocial burden

Background: Some patients with epilepsy develop intermittent and pleomorphic affective-somatoform symptoms, termed interictal dysphoric disorder (IDD). Other psychiatric disorders have been extensively investigated in patients with epilepsy, but there are few clinical studies investigating the comorbidity patterns of IDD and common psychiatric disorders (PDs). In particular, the impact of IDD on the psychosocial burden of patients remains unclear. Methods: The participants were 128 adult Japanese outpatients with localization-related epilepsy (LRE). In order to determine the comorbidity patterns for IDD and PDs, we conducted a comprehensive diagnostic investigation for IDD and DSM-IV psychiatric disorders. Based on these analyses, participants were divided into groups according to the comorbidity patterns for IDD and PDs in order to compare both suicide risk and quality of life (QOL). Results: The findings indicated that 19.5% of participants had IDD, and 55.5% had PDs. Younger age at epilepsy onset and refractory complex partial seizures were associated with IDD, but the duration and type of epilepsy were not. Patients with IDD were more likely to have comorbid PDs as follows: mood disorders (odds ratio, OR: 8.30; 95% confidence interval, CI: 3.15-21.83), anxiety disorders (OR: 8.81; 95% CI: 3.30-23.49), and psychotic disorders (OR: 7.72; 95% CI: 2.83-21.06). Group comparisons demonstrated that there were no patients with IDD but without PD. Furthermore, patients with IDD and with PDs had a significantly higher suicide risk and lower QOL compared to the other groups, even after adjusting for the influences of confounding factors. Conclusion: Interictal dysphoric disorder adds extreme psychosocial burden and is associated with multiple PDs in patientswith LRE. The present study suggests that IDD has a specific prognostic significance. However, whether IDD is nosologically independent fromconditions diagnosed using standardized psychiatric diagnostic systems such as DSM-IV must be further assessed by future research. (C) 2015 Elsevier Inc. All rights reserved.