EPIDEP: Prevalence of undiagnosed depression in an epilepsy outpatient clinic

Epilepsy and depression frequently coexist, with depressive symptoms affecting up to 50 % of patients, particularly those with drug-resistant epilepsy (DRE). Underdetection of depression in general neurology settings can worsen seizure control, treatment adherence, and overall prognosis. This study aimed to characterize the prevalence of undiagnosed depression in epilepsy outpatients and to evaluate the Neurological Disorders Depression Inventory for Epilepsy (NDDIE) as a screening tool, as well as the impact of early SSRI treatment. In a single-center, observational, non-interventional, prospective design, 82 consenting adults (mean age 50.8 ± 23 years; 59.8 % female) with diagnosed epilepsy (focal, idiopathic generalized, or unknown onset) and no prior psychiatric history or antidepressant use were enrolled over one year. Participants completed the NDDIE at baseline; those screening positive (score > 13) began SSRI therapy and were referred to psychiatry for diagnostic confirmation. Repeat NDDIE assessments occurred at three months. Of 82 patients, 35 (42.7 %) screened positive on NDDIE and 24 (29.3 % overall) were confirmed depressed by psychiatry (κ = 0.71). Baseline mean NDDIE was 12.17 ± 5.46, decreasing to 10.78 ± 4.36 at three months across all participants (Δ = 1.39; p < 0.05). In treated patients (n = 35), NDDIE fell from 17.83 ± 2.74 to 14.74 ± 3.48 (Δ = 3.09; p < 0.001). Patients with DRE (n = 10) had higher baseline scores than non-DRE (19.40 ± 1.96 vs 11.00 ± 5.40; p < 0.05) and those on ≥ 2 anti-seizure medications (ASM) scored higher than monotherapy (17.52 ± 4.08 vs 9.82 ± 4.20; p < 0.001). Patients > 60 years had lower scores than younger patients (10.68 ± 4.58 vs 13.23 ± 5.82; p < 0.05). No sex or epilepsy type differences were significant. Depression is common and underdiagnosed in epilepsy outpatients, especially among those with DRE or on multiple ASMs. The NDDIE demonstrates good agreement with psychiatric diagnosis and detects clinically meaningful improvements following early SSRI treatment. Systematic depression screening using NDDIE in neurology clinics is recommended to identify and treat comorbid depression, potentially improving quality of life and seizure outcomes.