The authors stated that eight RCTs were included in the review; four included in the quantitative synthesis and four included in the qualitative synthesis. However, whilst four RCTs were included in the quantitative synthesis (315 patients), only three other RCTs (77 patients) were described in the results.
Two good quality RCTs compared CBIT with supportive psychotherapy (248 patients). Patients who received the CBIT had a significantly greater improvement on the Yale Global Tic Severity Scale after 10 weeks of treatment (3.66 points, 95% confidence interval 2.25 to 5.07). They were also more likely to achieve a score of "much improved" or "very much improved" on the clinical global impression of change scale (OR 6.01, 95% CI 3.13 to 11.53), corresponding to a number-needed-to-treat of 3.1 to achieve one additional "much improved" or "very much improved" outcome. No significant heterogeneity was observed (Ι²=0%).
Two RCTs compared habit reversal therapy with supportive psychotherapy (67 patients); both trials were considered to be at risk of bias due to lack of blinding of outcome assessors. Patients who received habit reversal therapy had a significantly greater improvement on the Yale Global Tic Severity Scale after five months of treatment (10.52 points, 95% CI 7.44 to 13.59). No significant heterogeneity was observed (Ι²=0%).
One RCT each compared habit reversal therapy versus exposure with response prevention, CBIT delivered face-to-face versus CBIT delivered via video-conference and habit reversal therapy versus waiting list control. Results of the individual trials were reported.