Professor O’Brien is a medical specialist in neurology and clinical pharmacology, with particular expertise in epilepsy and related brain disorders, anti‐epileptic drugs and imaging in animal models and humans.  His research covers both basic and clinical studies related to epilepsy, its neuropsychiatric co‐morbidities and other neurodegenerative brain diseases. He has published more than 290 peer‐reviewed papers, which have been highly cited and influenced clinical practice.  His work has had two primary goals:  First to better understand the determinants of treatment response in epilepsy, identify markers for treatment outcomes, and develop new treatment approaches, and second to investigate the fundamental neurobiological basis, and inter-relationship, of the neuropsychiatric co‐morbidities present in many patients with epilepsy.