Table 1.

Summary of included studies.

Reference	Design, number of arms, comparator, sample size and study location, setting	Sample demographics and baseline tic severity	Intervention and modality	Length/ dosage, follow-ups	Comorbidities	Outcome measures	Human support with intervention	Adherence and engagement	Summary of main findings
Himle, et al. (12)	RCT 2 arms, F2F CBIT, N = 20, USA, clinic	Children (8-17 yrs old, M = 11.6), 94% male, 28% on tic medication, 67% TS only, baseline YGTSS-TTS = 23.7	Internet-accessed Videoconference (Skype) CBIT	8 weekly sessions of CBIT delivered over 10 weeks. FU = post-treatment (week 10), and at 4-months	33% anxiety, 28% ADHD, 22% OCD	YGTSS*, CGI-S and CGI-I, PTQ, WAI, TAQ	Therapist supported	2 dropped out before primary analysis; both in F2F group	The intervention group showed a mean YGTSS-TTS reduction of 7.8 points and the F2F group showed a mean reduction of 6.5 points. Within-group ES for the two treatment delivery modalities were ES = 0.54 and ES = 0.75, for intervention and F2F. The intervention group showed a mean YGTSS-TTS reduction of 6.4 points at follow-up and the F2F group showed a mean reduction of 4.2 points. Within-group effect sizes for the two delivery modalities were ES = 0.39 and ES = 0.41, for intervention and F2F.
Ricketts et al. (16)	RCT 2 arms, WLC, N=20, USA, clinic and home based	Children (8-16 yrs old, M=12.1), 64.9% male, 95.8% Caucasian, 35% on tic medication, 75% TS only, baseline YGTSS-TTS = 25.75	Internet-accessed Videoconference (Skype) CBIT	Treatment consisted of two 1.5-h sessions followed by six 1-h sessions occurring over a 10-week period. FU = 10-week post treatment	25.8% ADHD, 8.3% OCD	YGTSS*, CGI-I, PTQ, CPTR, CSQ, TAQ, VSQ	Therapist and parent supported	Only 1 patient discontinued treatment as they sought treatment for OCD instead	In the intervention group there was a statistically significant decrease of 7.25 points in YGTSS-TTS total scores from baseline to post-assessment. In the WLC group, the 1.75-point decrease on the YGTSS-TTS total scores from baseline to post-assessment was not significant.
Andrén et al. (17)	Pilot RCT 2 arms, No comparison between groups, N = 23, Sweden, home based	Children (8-16 yrs old, M = 12.3), 65% male, 17.5% on tic medication, baseline YGTSS-TTS = 23.6	Internet delivered ERP and HRT	10 chapters over 10 weeks. FU = post-treatment and 3 (primary endpoint), 6 and 12-month	39% ADHD, 13% OCD	YGTSS*, CGAS, CGI-S and CGI-I, PUTS, GTS-QOL, adapted child version of the WSAS, OCI-Child version, CDI-S, PTQ, WSAS-Y (parent), SMFQ	Therapist and parent supported	Average number of completed chapters was 7.92 (for both children and parents) in the ERP group, and 7.36 (children) and 7.09 (parents) in the HRT group. 6 children (50%) and 5 parents (42%) in the ERP group, and 5 children and parents (45%) in the HRT group completed all 10 chapters. None lost to FU.	Significant reduction on the YGTSS-TTS for internet ERP, but not for internet HRT. Within-group Cohen's d was 1.12 for internet ERP and 0.50 for internet HRT.
Rachamim et al. (19)	Feasibility and effectiveness study with crossover design, 2 arms, WLC, N=41, Israel, home based	Children (7-18 yrs old, M = 11.26), 70.7% male, 24.4% on tic medication, baseline YGTSS-TTS = 22.72	Internet delivered CBIT	9 modules over 9 weeks. FU = post-treatment, 3 and 6-months	43.9% ADHD, 31.7% OCD	YGTSS*, CGI-I, CGAS, ADIS, PTQ, Revised CPRS, OCI, SCARED, LSAS, RSES, CDI	Therapist and parent supported	23 completed 9 modules. Participants completed a mean of 8.8/9 modules. Reasons for stopping (n = 2) included a lack of motivation and self-discipline.	A significant interaction was found for the YGTSS-TTS between time-point and group [F (1, 39) = 9.96, p = 0.003, large effect]. At post-intervention (time 2), the YGTSS-TTS was significantly reduced in the internet CBIT arm only. Internet CBIT was associated with a mean YGTSS-TTS reduction of 6.60 points (p < 0.001) compared with a mean YGTSS-TTS reduction of 0.94 points (p = 0.51) in the WLC arm. This 6.60 points difference was clinically meaningful, with an ES of within-group Cohen's d = 0.91, large effect.
Hollis et al. (18)	RCT 2 arms, Internet Psychoeducation, N = 224, UK, home based	Children (9-17 yrs old, M = 12), 79% male, 87% White, 13% on medication for tics, baseline YGTSS-TTS = 28.4	Internet delivered ERP	10–12 weeks of 10 chapters for both child and parent. FU = 3-, 6-, 12- and 18-months post-randomization	27% anxiety disorder, 25.5% ADHD, 22.5% ODD	YGTSS*, CGI-I, CGAS, CASUS, CHU9D, SDQ, PTQ, modified version of the Hill and Taylor side-effects scale, MFQ, SCAS, PUTS, C&A-GTS-QOL	Therapist and parent supported	204 (91%) received the minimum intervention (at least first 4 chapters) and were treatment completers (99 in the ERP group and 105 in the psychoeducation group). 186 (83%) were followed up 6 months after randomization (93 in the ERP group and 93 in the psychoeducation group).	Mean total decrease in YGTSS-TTSS at 3 months was 4.5 (16%) in the ERP group vs. 1.6 (6%) in the psychoeducation group, and at 6 months was 6.9 (24%) in the ERP group vs. 3.4 (12%) in the psychoeducation group. The estimated mean difference in YGTSS-TTSS change between the groups at 3 months was −2.29 points (95% CI −3.86 to −0.71) in favor of ERP, with an ES of −0.31 (95% CI −0.52 to −0.10)
Haas et al. (20)	RCT 3 arms, Placebo and F2F CBIT, N = 161, Germany, home based	Adults (112 males, 49 females, mean age = 35.6 yrs old, range = 18–62 yrs), 40.4% on tic medication, baseline YGTSS-TTS = 24.37	Internet delivered CBIT	8 sessions over 10 weeks. FU = 5 weeks after start of treatment (V2), 1 week after end of treatment (V3; primary endpoint), and 2 follow-up visits at 3 (V4) and 6 months (V5)	Not reported	YGTSS*, Modified RVBTRS, Adult Tic Questionnaire, GTS-QoL, PUTS-9, CGI-S and CGI-I, Y-BOCS, Conners' Adult ADHD Rating Scales, BDI-II, BAI, WAI-SR	No human support	108 (67.1%) were considered as compliant until V3. Rate of non-compliance was lowest in the placebo group (22.9%) and similarly high in both treatment groups	Internet CBIT group showed a larger tic reduction [2.54 (−3.53; −1.55)] in comparison to the placebo group [−1.26 (−2.16; −0.35)] at V3. Difference in YGTSS-TTS change to baseline between placebo and internet CBIT was −1.28 (−2.58; 0.01). Significance for superiority of internet CBIT was narrowly missed and the null hypothesis could not be rejected as the upper 95% CI limit was marginally above 0. Difference in YGTSS-TTS change to baseline between internet CBIT and F2F CBIT at V3 was 0.98 [−1.01; 2.96]. Since the upper bound of the 95% CI was below the non-inferiority margin of 3; non-inferiority of internet CBIT in comparison to F2F CBIT could be observed.

^*Primary outcome measure. ADHD, attention deficit hyperactivity disorder; ADIS, Anxiety Disorders Interview Schedule; CBIT, Comprehensive Behavioral Intervention for Tics; CDI, Children's Depression Inventory; CGAS, The Children's Global Assessment Scale; CGI-I, Clinical Global Impression-Improvement Scale; CGI-S, The Clinical Global Impression-Severity scale; CHU9D, Child Health Utility instrument; CPRS, Child-Parent Relationship Scale; CPTR, Children's Perception of Therapeutic Relationship; CSQ, Client Satisfaction Questionnaire; ERP, Exposure and Response Prevention; ES, effect size; F2F, Face-to-face; FU, Follow-up; GTS-QOL, Gilles de la Tourette Syndrome-Quality of Life Scale; HRT, Habit Reversal Therapy; LSAS, Liebowitz Social Anxiety Scale; MFQ, Mood and Feelings Questionnaire; OCD, obsessive compulsive disorder; OCI, Obsessive-Compulsive Inventory; ODD, Oppositional defiant disorder; PTQ, Parent Tic Questionnaire; PUTS, Premonitory Urges for Tic Disorders Scale; RCT, randomized controlled trial; RSES, Rosenberg's Self-Esteem Scale; RVBTRS, Rush Video-Based Tic Rating Scale; SCARED, Screen for Child Anxiety Related Disorders; SCAS, Spence Children's Anxiety Scale; TAQ, Treatment Acceptability Questionnaire; TAU, Treatment as usual; TS, Tic syndrome; TTS, Total Tic Score; VSQ, Videoconferencing Satisfaction Questionnaire; WAI, Working Alliance Inventory; WLC, wait-list control; WSAS, Work and Social Adjustment Scale; YGTSS, Yale Global Tic Severity Scale.