Interictal Dysphoric Disorder: A disorder with distinct nosography or atypical symptomatology of mood disorders in people with epilepsy? Results from a systematic review.

INTRODUCTION: Mood disorders are the most frequent comorbidities in people with epilepsy. The term Interictal Dysphoric Disorder (IDD) has been used to describe a condition where at least three out of eight symptoms must be present for diagnosis. Symptoms are grouped into three symptom clusters of four "labile depressive" symptoms (anergia, depressed mood, insomnia, and pain), two "labile affective" symptoms (anxiety and fear), and two specific symptoms (euphoric moods and paroxysmal irritability), which are described and can be present in people with epilepsy. There is debate about whether IDD is a distinct disease, or if it is simply a special manifestation of mood disorders in epilepsy. For instance, it may represent an atypical presentation of depression in this population. METHODS: We conducted a systematic review of the literature in 3 databases with the terms "Interictal Dysphoric Disorder" and "mood disorder". A total of 130 articles were selected and, after removing the duplicated applying eligibility criteria, 12 articles were included. RESULTS: Six articles showed positive evidence for the validation of IDD as an independent nosological entity; in contrast, five articles reported inconclusive findings regarding the question; one explicitly questioned significant differences between IDD and mood disorders as nosological constructs. The data available and presented in this systematic review is insufficient to confirm IDD as a distinct diagnostic category. Nevertheless, it is worth noting other researchers have found some validity in this concept, highlighting the strong connection between mood disorders and epilepsy. CONCLUSION: Further research in this area is needed, and additional systematic reviews focusing on other aspects of the construct, such as neurobiological mechanisms, may prove to be helpful.