His areas of expertise are self-injury and youth mental health. He has co-authored a book on self-injury and his research has been featured in national and international media outlets, including The New York Times, Time, USA Today, ABC, CBS, The Globe and Mail, and the BBC. Dr. Lewis is an invited member of the International Society for the Study of Self-Injury (ISSS), where he currently sits on the Executive Board. His work in the area of self-injury led to him co-founding Self-injury Outreach and Support (SiOS), with his colleague Dr. Nancy Heath (McGill University). SiOS an international non-profit initiative providing current information and helpful resources about self-injury to those who self-injure, those who have recovered, as well as their caregivers and families, friends, teachers and the health professionals who work with them.