Investigators found reductions in tic frequency and increases in the number of tic-free intervals when children were merely asked verbally to suppress their tics, and when an immediate and contingent reward was delivered for successful tic suppression, tic suppression was enhanced.
Soyoung Kim, PhD
Recent results from the NewTics study suggest that better ability to suppress tics within months of tic onset may be a predictor of future symptom outcomes in patients with tic disorders.1
Ultimately, 45 children who were a mean age of 7.74 years with a mean of 3.47 months since their tic onset showed a better tic severity at their 12-month follow-up visit when they were able to suppress tics in the presence of a reward. Tic suppression was also found to be particularly successful when patients received a contingent reward.
“The most important finding in the present study is that rewarded tic suppression measured within months of tic onset predicts future tic severity,” Soyoung Kim, PhD, and colleagues wrote. “Specifically, in children with recent-onset tics, we found that those children with better tic suppression in the presence of a reward had lower tic burden at the 1-year anniversary of tic onset, the time when a persistent tic disorder can first be diagnosed. Thus, we have identified a potential predictor of clinical outcome in provisional tic disorder.”
Kim, postdoctoral research associate, department of psychiatry, Washington University School of Medicine, et al. noted that successful voluntary tick suppression is key to behavioral interventions in tic disorder treatment, and previous study has suggested that even those children with provisional tic disorder who had tics for <6 months can successfully suppress tics, especially in the presence of a contingent reward.
Participants completed a set of 2, 5-minute sessions under 3 conditions, performed in a fixed order. Then, the second session was presented in a counterbalanced order. The sessions were as follows: free tic, in which participants were instructed to sit in a chair and tic as needed; verbal instruction, in which they were instructed to suppress their tics; and Differential Reinforcement of Other behavior (DRO), defined as zero-rate ticking, in which they were instructed to suppress tics, and told that they would receive a token for every 10 seconds that a tic was not detected.
All told, both suppression conditions, verbal and DRO, significantly differed from the free tic condition in both tic frequency and tic-free intervals (P <.05), with the DRO condition also differing from the verbal condition in both tic frequency and tic-free intervals (P <.05).
As for 12-month follow-up, Yale Global Tic Severity Scale total score was predicted significantly by the tic suppression interval in the DRO condition (R2 = .277; F(3, 33) = 4.22; P = .01; adjusted R2 = .212), with suppression interval being a significant predictive factor (P = .038). As well, tic suppression frequency in the DRO condition was similar (R2 = .246; F(3, 33) = 3.59; P = .02; adjusted R2 = .177), though frequency was not a significant predictor (P = .09).
“With this larger sample, we also detected a significant association between age and rewarded tic suppression,” the investigators wrote. Previous work from Conelea et al. suggested that age effects could be in part due to longer illness duration, which could imply more opportunities to practice tic suppression. Notably, for these results, this does not appear to hold, as all but 1 patient in the NewTics study had tics for <6 months.
“We contend that the age-dependent effects found in the current study are more likely due to inhibitory control maturation during development. Age-dependent effects in inhibitory control have been repeatedly reported in healthy children in both behavioral and brain imaging studies,” they noted.
As well, the results showed a significant relationship between the Premonitory Urge for Tics Scale score and tic suppression frequency in the presence of reward. Those with high scores showed relative success in tic suppression, while lower scores resulted in varying degrees of suppression. As such, Kim and colleagues concluded that these results “are consistent with the idea that experiencing the premonitory urge may help tic suppression.”
Kim S, Greene DJ, Robichaux-Viehoever A, et al. Tic Suppression in Children With Recent-Onset Tics Predicts 1-Year Tic Outcome. J Child Neurol. Published online June 26, 2019. doi: 10.1177/0883073819855531.