Anhedonia in epilepsy

Anhedonia, the impaired ability to experience pleasure, is a core feature of major depressive disorder, one of the most common comorbidities in epilepsy. It is also reported as a clinical feature independent of depression in a number of other neurological conditions. This study aimed to establish the prevalence of anhedonia in a sample of people with epilepsy, with and without a diagnosis of depression, and to examine the clinical and demographic characteristics of those who present with this symptom.

A consecutive sample of 211 people (118 female, 93 male, mean age 38.09 years) completed the Snaith-Hamilton Pleasure Scale (SHAPS) to determine the presence of anhedonia and the Hospital Anxiety and Depression Scale to determine levels of anxiety and depression. The majority of patients had focal epilepsy (n = 165), and the remaining patients had generalized epilepsy (n = 22), or unclassified epilepsy (n = 24). Sixteen percent of the sample had a clinical diagnosis of depression at the time of the study.

Over one in three of the sample (35%) reported significant anhedonia on the SHAPS. While these patients were more likely to have a diagnosis of depression (p < 0.01), 30% of people without a diagnosis of depression also reported significant anhedonia. Difficulties gaining pleasure on 12 of the 14 items on the SHAPS were associated with cognitive difficulties, with those reporting an inability to feel pleasure on the item scoring significantly lower on tests of cognitive function than those who were able to gain pleasure. Of the three cognitive domains examined (overall intellectual ability, verbal memory, and processing speed), a poor memory had the strongest relationship; with lower memory function associated with an impaired ability to experience pleasure on 9 of the 14 items.

While anhedonia is well recognized as a feature of depression, our data suggests that it can be present in up to a third of people with epilepsy who do not have a diagnosis of depression. Cognitive difficulties, particularly impaired memory function may mediate some features of anhedonia. The implications of these findings for the clinical management of anhedonia in people with epilepsy are discussed.