Robert D. Levitan, M.D., is a Psychiatrist at the Centre for Addiction and Mental Health, and a Professor of Psychiatry and Physiology at the University of Toronto, Toronto, Canada. Robert’s primary interest is the “atypical spectrum” of mood disorders which encompass both depression and overeating/obesity, including seasonal affective disorder (SAD). He studies the early developmental origins of these disorders, and the use of light therapy for various disorders that can be influenced by seasonal effects, including attention deficit disorder. The use of light therapy to phase advance delayed circadian rhythms in these patients is a particular focus of this work.