Center for Injury Research and Prevention

Stephen Leff, PhD

Stephen Leff, PhD, CHOP CIRP
Co-Director of CHOP's Center for Violence Prevention

Stephen Leff, PhD is a Psychologist at Children’s Hospital of Philadelphia (CHOP), Co-Director of CHOP’s Center for Violence Prevention, and a Professor of Clinical Psychology in Pediatrics and Psychiatry at the University of Pennsylvania Perelman School of Medicine. He is a nationally recognized leader in aggression and bullying prevention programming, relational aggression, and the community-based participatory research (CBPR) process, which works with community stakeholders to integrate their perspectives into best practice programming.

Dr. Leff’s research has developed and validated a number of aggression interventions for urban minority youth including playground- and lunchroom-based applications, small group interventions for relationally aggressive girls within the schools (Friend to Friend), universal prevention programs for 3rd-5th grade students delivered within the classroom (PRAISE), universal prevention programs for urban adolescents within community-based after-school settings, and a brief multi-media bullying prevention experience for middle school students (Free2B).  A range of different outcome assessment tools have also been developed through this same partnership-based research process and validated across samples.

Dr. Leff has been awarded five National Institutes of Health (NIH) grants and a Department of Education grant to support his aggression and bullying prevention programs in urban schools. He lectures frequently both regionally and nationally, and is a member of the National Bullying Research Network, as well as an Attending Psychologist at the Center for Management of Attention-Deficit/Hyperactivity Disorder (ADHD) at CHOP. Dr. Leff earned his PhD in Clinical Psychology from the University of North Carolina. He can be contacted at