EEG Microstate and Neuroinflammatory Biomarkers in Older Age Patients With Major Depressive Disorder Receiving ECT

Inclusion Criteria: Patient Group * Age ≥55 years. * Diagnosis of Major Depressive Disorder or Bipolar Disorder, current major depressive episode, according to DSM-5 criteria. * Clinical indication for electroconvulsive therapy (ECT). * Ability to provide written informed consent. * Willingness to participate in the study. Healthy Control Group: * Age ≥55 years. * No current psychiatric disorder. * No known neurological disorder. * Good general physical health. * No current use of medications known to affect EEG activity or inflammatory biomarkers significantly. * Ability to provide written informed consent. * Willingness to participate in the study. Exclusion Criteria: * Primary neurological disorders (e.g., dementia or traumatic brain injury). * Schizophrenia or other psychotic disorders. * Intracranial space-occupying lesions. * Increased intracranial pressure. * Myocardial infarction within the previous 3 months. * Cerebrovascular disease within the previous month. * Unstable cerebral aneurysm. * Pheochromocytoma. * Electroconvulsive therapy (ECT) or transcranial magnetic stimulation (TMS) within the previous month. * Cognitive impairment severe enough to prevent adequate cooperation during EEG recording. * Current alcohol or substance use disorder. * Active infectious disease. * Uncontrolled autoimmune or chronic inflammatory disorders. Participants with stable disease who had received the same maintenance treatment within the previous 3 months were eligible for inclusion.