The purpose of this study is to evaluate the feasibility and acceptability of two different modalities of therapist-guided Internet-delivered behaviour therapy (IBT) for children and adolescents (7-17 years) with Tourette's Disorder (TD) or Persistent (Chronic) Motor or Vocal Tic Disorder (PTD).

The primary objective of this study is to evaluate the feasibility and acceptability of two different modalities of therapist-guided Internet-delivered behaviour therapy (IBT) for children and adolescents (7-17 years) with Tourette's Disorder (TD) or Persistent (Chronic) Motor or Vocal Tic Disorder (PTD). The two modalities of IBT are habit reversal training (HRT) and exposure and response prevention (ERP). Secondary objectives are to evaluate whether IBT can decrease tic frequency and tic-related impairment, and, as both HRT and ERP have been proven efficacious in treating TD/PTD face-to-face, are any of the two treatments better suited to be delivered via the internet?

The design of the study is a randomized-controlled trial with 20 participants. Participants will be stratified by ADHD/ADD status.

The treatment duration is 10 weeks.

Feasibility and acceptability will be assumed if:

• The two treatments can be successfully adapted to a therapist guided internet-delivered format (technical feasibility)
• Patients/parents are willing to try the offered treatment modalities
• Participants complete the active parts of the treatment
• Referrers are open to the idea of internet-delivered treatment for TD or PTD
• We can recruit sufficient numbers of patients for a fully powered efficacy trial

Regarding the secondary objective, the primary outcome is tic severity measured by the Yale Global Tic Severity Scale (YGTSS). Participants will be assessed directly after treatment (post), and at 3, 6 and 12 months after treatment. Assessments at post-treatment and 3 month follow up will be performed by assessors blinded to the treatment condition. After 3 months, we will naturalistically follow up patients up to 12 months after the end of treatment. Data collection will finish 12 months after treatment.

Inclusion Criteria:

• Fulfill DSM-5 diagnostic criteria for Tourette's Disorder or Persistent (Chronic) Motor or Vocal Tic Disorder (PTD).
• >15 (TD) or >10 (PTD) on Yale Global Tic Severity Scale (Impairment not included).
• Both child and parent are able to read and communicate in Swedish.
• Regular access to a computer and the Internet.
• Parent availability to support their child throughout the treatment.

Exclusion Criteria:

• Acute psychiatric problems such as severe depression, suicidal risk, substance abuse or another psychiatric disorder that could interfere with treatment.
• Lifetime history of global learning disability, pervasive developmental disorder, psychosis, bipolar disorder or organic brain disorder.
• Severe tics causing immediate risk to the patients or others and requiring urgent medical attention.
• Previous behavioural therapy (HRT or ERP), minimum 8 sessions with qualified therapist, within the last 12 months prior to assessment.
• Simultaneous psychological treatment for tic disorder.
• Initiation or adjustment of any psychotropic medication for tics within the last 6 weeks prior to assessment.