This National Institute of Mental Health-funded project examined circadian rhythms and sleep disturbance in youth (10-17 years) with Tourette's disorder and healthy controls, and piloted the effects of wearable short-wavelength morning light therapy in the subset of youth (13-17 years) with Tourette's disorder. Results showed subjective (i.e., morningness-eveningness) but not objective (i.e., dim light melatonin onset) delays in circadian timing, and greater sleep disturbance per both self-report and actigraphy in youth with Tourette's disorder relative to controls. Following two weeks of morning light therapy, there were significant advances in objective (i.e., dim light melatonin onset) but not subjective (i.e., morningness-eveningness) circadian timing. There were significant improvements in subjective insomnia ratings, but not objective sleep (actigraphy). There were also significant reductions in tic severity and tic-related impairment, but no significant changes in anxiety, depressive symptoms, or daytime sleepiness.