Prevalence of psychiatric comorbidities in temporal lobe epilepsy: the value of structured psychiatric interviews

Although many studies have demonstrated a high prevalence of psychiatric disorders in epileptic patients, most have used unstructured psychiatric interviews for diagnosis, which may lead to significant differences in results. Here we present a study evaluating the prevalence of major psychiatric comorbidities in a cohort of South Brazilian patients with temporal lobe epilepsy using a structured clinical interview.

Neuropsychiatric symptoms were analyzed in 98 patients (39 men and 59 women) with temporal lobe epilepsy. Patient mean age was 43 years old, and mean duration of epilepsy was 25 years. Patients were diagnosed according to the ILAE Classification of Epileptic Syndromes using clinical, EEG, and neuroimaging criteria. All patients participated in the Structured Clinical Interview for DSM-IV (SCID).

Fifty-three patients (54.1%) presented major psychiatric comorbidities. Mood disorders were observed in 42 patients (42.9%), the most common being neuropsychiatric disorders. Anxiety disorders were the second most frequent disorders, observed in 18 patients (18.4%). Psychotic disorders and substance abuse were each observed in six patients (6.1%). There were no clinical variables regarding epilepsy characteristics (age of onset, duration, response to antiepileptic drugs) and no MRI features associated with psychiatric disorders. A seven-fold increased risk of mood disorders was identified in patients with inter-ictal EEG abnormalities associated with the left hemisphere.

Relative to previous reports, we identify a high prevalence of psychiatric disorders in TLE patients, although our data is similar to that observed in other studies which have used similar structured interviews in populations of epileptic patients attending tertiary centres. The wide variation in percentages is probably attributable to the different patient groups investigated and to the even greater variety of diagnostic methods. Structured psychiatric interviews may contribute to a better evaluation of the true prevalence of psychiatric comorbidities in temporal lobe epilepsy.