Interictal dysphoric disorder and periictal dysphoric symptoms in patients with epilepsy

The issue of phenomenology of mood disorders in epilepsy still remains controversial. It has been suggested that a subgroup of patients may develop an affective syndrome also known as interictal dysphoric disorder (IDD). However, the number of behavioral changes that may occur around the ictus needs to be taken into account for an accurate distinction between "true" psychiatric phenomenology and periictal phenomena. This study aimed at identifying clinical correlates of the IDD, with special attention to the relationship between symptoms and seizures.

A sample of 142 consecutive adult outpatients with epilepsy were assessed using the Interictal Dysphoric Disorder Inventory (IDDI), a 38-item, self-report questionnaire specifically developed to evaluate presence and severity of IDD symptoms as well as their habitual association with seizures (coded as before, after, during, or when seizure-free) and their duration.

IDD was diagnosed in 31 subjects but symptoms showed a clear-cut relationship with epileptic seizures in 54.8% of cases, leading to an operative distinction between true IDD and periictal dysphoric symptoms (PDS). There was no significant difference among patients with IDD, PDS, or those without psychopathology. In the IDD group, symptoms were chronic and unremitting in one-third of cases, with labile affective symptoms being correlated with age at onset of seizures (rho = -0.612, p = 0.020) and duration of the epilepsy (rho = 0.833, p < 0.001).

An operative distinction between IDD and PDS bears the opportunity to identify different clinical endophenotypes that may have different prognoses and require different treatment strategies.