This study examines circadian rhythms and morningness-eveningness preference in youth with Persistent Tic Disorders (PTDs), including Tourette's Disorder (TD); and assesses the effects of wearable short wavelength light therapy on circadian rhythms and tic symptoms.

Many individuals with Persistent Tic Disorders (PTDs), including Tourette's Disorder (TD) fail to significantly benefit from existing tic treatments. Case studies have shown morning exposure to light therapy, known to advance circadian phase is associated with modest to large tic reductions (Coles & Strauss, 2013; Niederhofer, 2003) suggesting the presence of circadian abnormalities (i.e., phase delay) in select individuals with PTDs. The present project assesses circadian phase and morningness-eveningness preference in youth with Persistent Tic Disorders (PTDs), including Tourette's Disorder (TD), and examines whether morning use of wearable short wavelength light therapy is associated with shifts in circadian rhythms and reductions in tic severity.

Study participation will take place over a three-week period. Clinician-rated tic interview and rating scales of morningness-eveningness preference, sleep, tic, and other symptoms will be completed during an initial screening assessment. Participants will then monitor sleep at home using an actigraph for one week and return for a baseline clinical assessment of tic severity and evening assessment of internal melatonin levels involving saliva sampling every 30 minutes for 6.5 hours in a dimly lit room. Next, participants will complete an abbreviated course (i.e., two weeks) of morning light therapy using wearable short wavelength (i.e., blue-green) light-emitting glasses while continuing to monitor sleep using the actigraph. Following this two-week period participants will return for a final assessment of tic severity and internal melatonin levels.

Inclusion Criteria:

1. DSM-5 diagnosis of Tourette's Disorder, Persistent Motor Tic Disorder, or Persistent Vocal Tic Disorder
2. Yale Global Tic Severity Scale Score ≥ 14 for Tourette's Disorder or ≥ 10 for Persistent Motor Tic Disorder or Persistent Vocal Tic Disorder
3. fluency in English

Exclusion Criteria:

1. Current or lifetime diagnosis of Bipolar Disorder, psychosis, or autism spectrum disorder
2. Suicidality, severe depression or anxiety (i.e., Depression or anxiety diagnosis is more severe than Tourette's Disorder; equivalence in severity is allowed), or substance dependence, present within the past 6 months
3. Current diagnosis of Obstructive Sleep Apnea, Restless leg syndrome, Periodic Limb Movement Disorder, or Narcolepsy
4. Intellectual functioning below the low average range (WASI-II IQ score < 80)
5. Hypnotic medications, or melatonin within 8 weeks of study enrollment
6. Changes in dosage of any psychiatric medications within the past month
7. Behavior therapy for tics within the past 3 months
8. Prior use of light therapy
9. Current pregnancy or travel across > 2 time zones in the past month
10. Medical or neurological condition (e.g., seizure disorder, migraines) that would interfere in the individual's ability to participate in the study