Prediction of treatment resistance in obsessive compulsive disorder patients based on EEG complexity as a biomarker

•EEG beta band complexity could be a biomarker for treatment resistance in OCD.•EEG beta band complexity was lower in treatment-resistant OCD patients.•Severity of illness as measured by Yale-Brown Obsessive Compulsive Scale was inversely correlated with approximate entropy (ApEn) complexity values. This study aimed to identify an Electroencephalography (EEG) complexity biomarker that could predict treatment resistance in Obsessive compulsive disorder (OCD) patients. Additionally, the statistical differences between EEG complexity values in treatment-resistant and treatment-responsive patients were determined. Moreover, the existence of correlations between EEG complexity and Yale-Brown Obsessive Compulsive Scale (YBOCS) score were evaluated. EEG data for 29 treatment-resistant and 28 treatment-responsive OCD patients were retrospectively evaluated. Approximate entropy (ApEn) method was used to extract the EEG complexity from both whole EEG data and filtered EEG data, according to 4 common frequency bands, namely delta, theta, alpha, and beta. The random forests method was used to classify ApEn complexity. ApEn complexity extracted from beta band EEG segments discriminated treatment-responsive and treatment-resistant OCD patients with an accuracy of 89.66% (sensitivity: 89.44%; specificity: 90.64%). Beta band EEG complexity was lower in the treatment-resistant patients and the severity of OCD, as measured by YBOCS score, was inversely correlated with complexity values. The results indicate that, EEG complexity could be considered a biomarker for predicting treatment response in OCD patients. The prediction of treatment response in OCD patients might help clinicians devise and administer individualized treatment plans.