Evidence-based psychological interventions
In the 2011 European clinical guidelines, behavior therapy (BT) was recommended as a first-line intervention for tic disorders in children and adults [5, 6]. The rationale for using BT for treating tic disorders is based on the fact that tics can be suppressed for various lengths of time, and that the expression of tics, beyond their neurobiological origin, is influenced by contextual factors. These contextual factors include the perception of premonitory urges and other internal (e.g. emotional) states and environmental contingencies (e.g. specific situations or activities, stress-inducers, social reactions). The goal of BT is to provide patients with tic-specific behavioral techniques to enhance self-control and to decrease factors that worsen or maintain tics.
Of the different BT interventions available, most experimental evidence was found for Comprehensive Behavioral Intervention for Tics (CBIT), where Habit Reversal Training (HRT) is considered the main component [7, 8]. Evidence was also found for Exposure and Response Prevention (ERP) . The 2011 European clinical guidelines recommended both HRT/CBIT and ERP as first-line interventions. In 2012, Canadian clinical guidelines were published, which also recommended BT as a first-line intervention for tic disorders, stating that especially CBIT is supported by strong evidence for efficacy and safety . Recently, the American Academy of Neurology (AAN) published their clinical guidelines for the treatment of tic disorders, again recommending BT as a first-line intervention for tic disorders. The AAN guidelines specify that clinicians should offer CBIT as an initial treatment option prior to other psychological interventions and to pharmacotherapy (PT). If CBIT is unavailable, ERP may be an acceptable alternative. According to the AAN guidelines, CBIT is the only intervention to achieve the highest rating (“high confidence” to reduce tics compared to the control condition), which was not achieved by any of the PTs .
The following sections describe clinical trials of psychological interventions, published since the 2011 European clinical guidelines, based on our current literature search. Table 1 presents details on randomized controlled trials (RCTs) published since 2011, as well as influential RCTs published prior to 2011. Treatments for tic disorders that were mentioned in the 2011 European clinical guidelines, but were not examined or supported by RCTs (such as massed negative practice, self-monitoring and relaxation training), and where no new substantial evidence has been published since are not covered in this update .
Psychoeducation refers to the clear sharing of understandable, up-to-date information about the symptoms, cause, prognosis, potential management, treatment and daily experience of a condition. Such information is typically included as a first step in various treatment protocols of evidence-based psychological interventions for tic disorders (e.g. [12, 13]). However, as a stand-alone intervention aimed at reducing tic severity, psychoeducation (sometimes also extended with information on healthy habits and common comorbid conditions, and referred to as psychoeducation and supportive psychotherapy [PST]) has been shown inferior to BT and PT in several RCTs [8, 14, 15]. In a review of psychoeducation for teachers and peers, it was concluded that psychoeducation increases knowledge, positive attitudes and behaviors towards individuals with TS .
Despite psychoeducation being described in clinical guidelines as a first important step of any treatment for TS [5, 11], evidence on what specific elements should be addressed is lacking. A comprehensive overview of suggested information to include can be found in a review by Wu and McGuire .
Habit reversal training (HRT) and Comprehensive behavioral intervention for tics (CBIT)
HRT consists of two primary parts: First, awareness training, which includes different techniques to increase awareness of tic expression and associated premonitory urges. Second, competing response training, in which physically incompatible responses are identified and applied, which prevent tics from being expressed. In HRT, tics are treated on a one-by-one basis. All current tics are listed and rated in terms of their severity. Typically, the most bothersome tic from this hierarchy is selected to be treated first. This tic is then subjected to awareness training, in which the patient learns to detect when the tic is occurring, as well as the signals that precede tic. Once a patient has developed a good awareness of the tic and can predict the occurrence of the tic, competing response training begins. Competing response training involves the selection and subsequent implementation of a physically incompatible behavior designed to prevent tics from occurring. The competing response generally employs the same muscles as the tic and should be able to be performed for a sustained period. Once a competing response has been practiced in a session, the patient continues to practice it at home. As soon as the patient learns to use the competing response to reliably prevent the tic, the treatment focus is shifted to the next tic in the hierarchy [12, 18]. CBIT is an expanded version of HRT, and additionally includes therapeutic strategies such as relaxation training, contingency management, and interventions based on functional analyses to address contextual factors which influence tic expression [8, 12].
The 2011 European clinical guidelines reported several RCTs of HRT/CBIT, demonstrating medium to large treatment effects. The largest RCT evaluated CBIT in 126 children (9–17 years) with TS or CTD . In this study, CBIT was superior to psychoeducation and PST in reducing tic severity (as measured by the Yale Global Tic Severity Scale - Total Tic Severity Score [YGTSS-TTS]; effect size: 0.68, as compared to PST). In a 6-month follow-up of treatment responders (defined as a score <3 on the Clinical Global Impressions–Improvement Scale [CGI-I]) of both groups, treatment gains were shown to be maintained for the majority of the responders in a completer analysis. In parallel to this trial, Wilhelm et al.  published an RCT in 2012 comparing CBIT with PST in 122 adults (16–69 years) with TS or CTD. In line with the pediatric trial, all patients received eight sessions of either condition, while responders additionally received three monthly booster sessions. As in the pediatric trial , CBIT was found to be superior to PST (effect size: 0.57). The responder rate (defined as CGI-I <3) was, however, lower in the adult trial (38.1% compared to 52.5% in the pediatric trial), which was hypothesized to reflect that the adult participants suffered from a more treatment-resistant form of the disorder. The overall dropout rate was 13.9%, with no difference between groups. Treatment responders of both groups continued to show benefits up to the 6-month follow-up, in a completer analysis.
The literature search also identified a few smaller clinical trials of HRT. Seragni et al. conducted a randomized pilot study (N=21) comparing HRT with a control condition (three sessions of routine treatment with a neuropsychiatrist, without prescription of PT) for young people with TS . Participants showed an improvement in tic reduction and global functioning in both groups, without significant between-group differences. Interpretation of the results was hampered by the small sample size and a high number of dropouts in both groups. Viefhaus et al. examined the efficacy of a German BT program (similar to CBIT) including HRT, psychoeducation and additional behavioral interventions (e.g. functional interventions) for young people (8–16 years; N=27) with TS/CTD . In a within-group design (8 weeks pre-treatment; 16 sessions treatment), significant improvements were found on tic severity (YGTSS-TTS, within-group effect size: 0.89) and tic-related impairment (YGTSS Impairment Score, within-group effect size: 0.31) at post-treatment. Bennett et al. evaluated a modified version of CBIT for use among very young patients (5–8 years) in an open study . Compared to the previously published CBIT protocol , the adaptations included fewer sessions (six instead of eight), larger parent involvement, and a simplified explanation of HRT through playing cards picturing body movements and competing responses. The results showed a medium-sized, significant within-group effect (d=0.73) on the YGTSS-TTS at post-treatment, which later was maintained at a 12-month follow-up. The study provides preliminary evidence for CBIT also being efficacious in this younger patient group.
Further adaptations to BT have been made to broaden the focus from reducing tic severity to improving the individual’s overall quality of life. McGuire et al. evaluated a modular treatment protocol (“Living with Tics”; LWT) that incorporates HRT with psychoeducation, problem-solving, distress tolerance, and coping at school, with the aim of improving resilience and reducing tic-related impairment . Preliminary findings of this intervention in youth (N=24) showed the LWT intervention to be efficacious in improving quality of life relative to a waitlist control (YGTSS Impairment Score, effect size: 1.50). Ten participants (83%) in the LWT condition were rated as treatment responders, compared to four participants (33%) in the waitlist condition. Treatment gains were maintained at a 1-month follow-up .
To summarize, several RCTs support the use of HRT/CBIT as an effective treatment for tics in children and adults with TS.
Exposure and response prevention (ERP)
Similar to HRT, ERP is based on learning theory. In ERP, the individual practices suppressing tics for prolonged periods of time (response prevention), with gradually increased exposure to premonitory urges and environmental factors (e.g. situations and activities) that are likely to induce tics, with the aim to increase urge tolerance and thereby reduce tics. Unlike HRT, no tic hierarchy needs to be created and all tics are worked with at the same time. In ERP, the patient is first trained to enhance tic suppression. A stopwatch is used to record tic suppression times and the patient is motivated to beat his/her record on each new trial. In the next phase, exposure is optimized by focussing on the premonitory urges, being exposed to stimuli that are known to elicit tics and practicing in various situations and activities. Meanwhile, the patient is instructed to keep resisting all tics. Apart from the in-session training, the patient is encouranged to continue practicing ERP on his/her own between the sessions [9, 23].
In the 2011 European clinical guidelines part III on behavioral interventions one RCT of ERP for the treatment of tic disorders was reported , where 43 children and adults (7–55 years) were randomized to either ERP or HRT. The results demonstrated comparable effects for both treatments (within-group effect sizes: 1.42 for ERP and 1.06 for HRT). Results were maintained up to a 3-month follow-up, but the interpretation is hampered by cross over between treatments. Since 2011, only open studies have been published examining the treatment effects of ERP. In a naturalistic study by Andrén et al. , 74 participants (6–17 years) received BT at a TS specialist clinic in Sweden. Out of the 74 participants, 46 received ERP, 14 received HRT, and 14 received various combinations of the two. Results showed a significant and large within-group effect (d=1.03) on the YGTSS-TTS for the combined BT group at post-treatment, with further improvement at a 12-month follow-up. The study provides some additional open data on the efficacy of mainly ERP, but primarily the authors conclude that BT can be delivered in a naturalistic specialist clinical setting, with comparable effects to RCTs.
To date, there are no RCT data supporting cognitive interventions as a stand-alone treatment for TS. Since the 2011 European clinical guidelines, a new treatment model has been proposed by O'Connor et al. involving cognitive-behavioral and psychophysiological elements . This model describes an association between maladaptive beliefs about tics, premonitory urges, perfectionistic personality traits and negative psychophysiological consequences, such as elevated muscle tension in body areas where tics occur. The cognitive psychophysiological treatment developed by O’Connor et al. is a combination of sensorimotor activation and (meta-) cognitive interventions to target the proposed affected areas. So far, two open trials have been published in 36 adults and seven children with TS, indicating tic severity reduction after treatment [25, 26]. While being a possibly promising new treatment approach, RCT data are needed to determine the treatment effects.
Third-wave interventions represent both an extension of and deviation from traditional cognitive-behavioral approaches, and include concepts such as metacognitive training, mindfulness and psychological flexibility, as part of behavioral treatments. The acceptance-based approach, which is shared by several third-wave interventions, prioritizes the promotion of health and well-being and suggests that rather than trying to control aversive psychological, emotional or physiological symptoms, accepting them might reduce their negative impact. . So far, only a few studies have targeted the feasibility and efficacy of third-wave interventions for the treatment of patients with TS. A pilot study by Franklin et al. evaluated the feasibility of a combined treatment of HRT and acceptance and commitment therapy (ACT) in a small sample of adolescents with TS/CTD (N = 13; 14–18 years), showing comparable results to traditional HRT . Reese et al. tested the feasibility and efficacy of a modified form of mindfulness-based stress reduction (MBSR-tics) in a small open trial of adolescents and adults (16–67 years; N = 18) with TS/CTD . Fifty-nine percent of the participants were classified as treatment responders and results were maintained up to the 1-month follow-up. In a later study, Reese et al. modified the MBSR-tics intervention for online delivery . In this open study (26–59 years; N = 5), the intervention was judged feasible and acceptable. However, effects on tic severity and tic-related impairment from baseline to post-treatment were modest. The authors especially point out that participant adherence to homework assignments, in this online format, was lower than anticipated.
The acceptance-based approach has also been tested with a focus on premonitory urge sensations. In an experimental study, 45 young people (8–17 years) participated in three different two-minute-conditions: free-to-tic (baseline), tic suppression and urge acceptance . Results showed a significantly higher decrease in frequency and intensity of premonitory urges in the urge acceptance condition, compared to the other conditions. Additionally, the level of discomfort was found to be significantly lower during the urge acceptance condition compared to the tic suppression condition.
Another third wave intervention is resource activation, which has been evaluated in a within-subject pilot trial for young people (8–19 years; N = 24) with TS/CTD . The treatment focuses on the strengths and abilities of the patients and includes relaxation and mindfulness techniques. The trial showed significant reductions of tic severity and tic-related impairment, indicating that resource activation is a potentially effective treatment for patients with TS.
These pioneer studies indicate the potential feasibility of third-wave interventions for TS, however, RCTs are needed to determine efficacy and make recommendations for their use.
BT and PT
Only one RCT comparing the effects of BT to PT on tic severity has been published to date. Rizzo et al. randomized 110 young people (8–17 years) into three groups: BT (either HRT or ERP), PT (either risperidone, aripiprazole or pimozide), and psychoeducation . Data were available for 102 participants (BT: n=25; PT: n=53; psychoeducation: n=24). At post-treatment, tic severity (as measured by the YGTSS-TTS) improved significantly in the BT and PT groups compared to the psychoeducation group (between-group effect sizes: 1.42 for BT and 0.84 for PT [calculated from data presented in the original article]). The larger effect size in the BT group compared to the PT group may partially be explained by differences in baseline tic severity. In the same vein, there were no significant differences between the BT and PT groups at the same measure, indicating that BT and PT potentially could be equally effective. While these results are important, replication studies are warranted given the limitations of this RCT. These include low statistical power to assess between-group differences in the three conditions and the lack of intention-to-treat data.
Originating from animal study findings, cognitive enhancers such as D-cycloserine (DCS) are hypothesized to strengthen newly learned associations, which in turn may augment the treatment effects of BT. In a preliminary RCT , McGuire et al. randomized 20 participants (8–17 years) to one session of HRT plus 50 mg of DCS or one session of HRT plus placebo. The study found a significant between-group effect (in favor of the HRT plus DCS-group) on the Hopkins Motor/Vocal Tic Scale, for the two bothersome tics targeted in the HRT treatment. Limitations include not providing a full dose of HRT treatment and not including the YGTSS as an outcome measure. Further studies are needed to establish the possibly augmenting effect of DCS on BT.
Meta-analyses of BT
In recent years, as more RCTs on the efficacy of BT have been published, a number of systematic reviews and meta-analyses have been undertaken [34,35,36,37,38]. The studies range from an early meta-analysis by Wile et al.  including 4 RCTs to the most recent meta-analysis by Yu et al. , which summarized 10 RCTs exclusively of HRT and CBIT. The latter meta-analysis included a total of 586 participants and found a medium effect size for HRT (SMD = 0.43). Additional subgroup analyses indicated no differences in the therapeutic effect comparing mode of delivery (face-to-face vs. online) or age group (children vs. adults). Notably, Yu et al. defined strict inclusion criteria, such as only including studies which employed the YGTSS, thus resulting in some earlier trials being excluded (e.g. ). A meta-analysis by McGuire et al. , which was published 6 years earlier, employed less strict criteria (summarizing 8 RCTs, with N = 438), and reported a slightly larger medium effect size (SMD = 0.67) for BT.
Regarding other types of psychological interventions, a meta-analysis by Hollis et al.  found no evidence for tic-specific effectiveness of relaxation training, parent training, or anger control training.
Predictors and moderators of response to BT
A few studies have examined, primarily in a post-hoc fashion, predictors and moderators of response to BT for tic disorders. In a meta-analysis including pediatric and adult trials, McGuire et al. found that BT had larger treatment effects among trials with older average participant age, more therapy sessions, and with less co-occurring attention-deficit/hyperactivity disorder (ADHD), while concurrent PT for TS did not influence the treatment effects . However, findings regarding the impact of ADHD on therapy are equivocal. Conelea et al. , using data from experimental settings, showed that young people (5–17 years) with ADHD can suppress tics just as effectively as those without ADHD.
Sukhodolsky et al. examined predictors and moderators of treatment in BT and PST . The study showed that positive participant expectancy and greater tic severity predicted greater tic improvement in both groups, while comorbid anxiety disorders and greater premonitory urge severity predicted a lower tic improvement . The presence of PT for TS predicted tic reduction in the PST group, but not in the BT group. Taken together, the available studies suggest that PT for TS does not influence the treatment effects of BT. In another study, based on data from the same original RCTs as used in the Sukhodolsky et al. study, Essoe et al. concluded that adherence to homework assignments predicted tic reductions and treatment response .
Using data from a randomized trial evaluating a combination of HRT and ERP (described in more detail in a later section) , Nissen et al. investigated possible predictors and moderators of treatment response . Their data suggest that internalizing symptoms (anxiety) predicted a lesser reduction in functional impairment and that participants’ (negative) beliefs about their tics were shown to have a negative effect on treatment outcome.
More studies are needed to replicate and further deepen the understanding of potential predictors and moderators of response to BT for patients with TS.
Neurobiology of BT
So far, only one study has investigated neurobiological changes following the use of BT in TS. Deckersbach et al.  used functional magnetic resonance imaging (fMRI) to investigate 8 subjects who participated in a large CBIT trial  matched with 8 healthy controls. fMRI was conducted pre- and post-treatment in conjunction with a visuospatial priming task to measure response inhibition. The authors found a decrease of striatal activation in the putamen at the post-treatment assessment, which formed a hypothesis that BT leads to a normalization of activation in the putamen. A further finding was a negative correlation between change in tic severity (as measured by the YGTSS-TTS) and a region in the inferior frontal gyrus. A similar more recent study by Petruo et al.  used an inhibitory control task to investigate the hypothesis that patients with TS (n = 21) exhibit an increased perception–action binding  as compared to healthy controls (n = 21). Indeed, patients exhibited an impaired performance on the task at baseline, which was normalized after the CBIT intervention.
Novel modalities of established behavioral treatments
Given the limited availability of therapists trained in delivering BT for patients with tic disorders , focus on dissemination and adaptation of treatment delivery has increased in recent years. New modalities have been proposed to make BT more accessible, primarily by reducing the number of therapists needed and/or reducing the need for travel. The modalities fall into three main areas: group delivery; videoconference delivery; and internet delivery. Additionally, there are case series using intensive treatment delivery schedules to reduce travel time.
Group delivery of BT
Group delivered BT for patients with TS has emerging evidence to date. Yates et al. compared two 8-session group interventions (CBIT [n = 17] vs psychoeducation [n = 16]) among children (9–13 years) with TS . The results showed a reduction in motor tic severity at post-treatment (effect size: 0.55, in favor of the CBIT group). None of the groups showed a significant reduction in vocal tic severity. The observed treatment effects on tic severity and quality of life were maintained at a 12-month follow-up . Interestingly, both groups reported a higher rate of school attendance in the year following treatment as compared with the year before the intervention. In this study, meeting other young people with tics did not increase tic expression, which is a common fear expressed by parents and patients.
Zimmerman-Brenner et al.  compared group-delivered CBIT to group-delivered psychoeducation in a RCT (8–15 years; N = 61). Participants received 8 weekly sessions during the acute treatment phase and 3 additional monthly sessions during a 3 months follow-up phase. Results showed no significant between-group effect on the YGTSS-TTS at post-treatment, but significant within-group improvements on the YGTSS Motor Tic Severity Score and the YGTSS Impairment Score for both groups. Interestingly, tic severity as measured by the YGTSS-TTS increased in both groups at post-treatment. This effect was seemingly driven by a significant increase in vocal tic severity, which could have been a side effect of the group format. At the 3-month follow-up, however, both groups showed improved YGTSS-TTS scores compared to baseline, indicating that the worsened vocal tic severity was temporary. Further, only the CBIT group showed a maintained improvement on the YGTSS Motor Tic Severity Score at the 3-month follow-up, indicating a possible benefit for this active treatment.
Nissen et al. conducted a randomized trial comparing a combination of HRT and ERP in young people (9–17 years; N = 59) in either an individual setting or a group setting . Both settings involved nine sessions, where HRT was introduced before ERP, and the final sessions were devoted to the type of BT that seemed most effective for that specific participant. The study showed significant tic severity reductions in both settings (within-group effect sizes: 1.21 for the individual setting and 1.38 for the group setting). A total of 66.7% of the participants were considered treatment responders (defined as a 25% reduction on the YGTSS-TTS). There was no statistically significant difference between the groups, apart from the YGTSS Impairment Score (in favor of the individual setting). The within-group treatment effects were maintained for both groups at a 12-month follow-up .
Lastly, in an open pilot study by Heijerman-Holtgrefe et al.  (9–14 years; N = 14), ERP was evaluated in an intensive group format (12 sessions fitted into 3 + 1 days). This so-called “Tackle your tics”-programme further included coping strategy workshops led by young adult patients, relaxation training, and separate parent meetings. The results showed a significantly decreased tic severity (YGTSS-TTS) between baseline and a 2-month follow-up (ηp2 = 0.41), increased quality of life and high treatment satisfaction.
To summarize, studies of group delivery of BT have shown mixed results. More studies are needed to make firm recommendations for clinical practice.
Videoconference delivery of BT
Videoconference BT is identical to regular face-to-face BT, except for that the (real time) communication between the patient and therapist is made via videoconference software. Two pilot RCTs have evaluated CBIT via videoconference delivery [54, 55]. Himle et al. compared videoconferencing (received at a clinic) to face-to-face delivery (8–17 years; N = 20) and found that tic severity was reduced regardless of the CBIT modality, with similar within-group effects at a 4-month follow-up . Ricketts et al. compared videoconferencing (received at home via the software Skype) to a waiting-list control condition (8–16 years; N = 20), and found a greater tic severity reduction in the videoconferencing group, compared to the waiting list condition . Although some challenges (like video/audio problems and difficulties viewing homework) were described , both studies reported strong therapeutic alliance ratings, treatment satisfaction, and videoconferencing satisfaction in the videoconferencing groups [54, 55]. These findings suggest that videoconferencing is a feasible and acceptable format for the delivery of BT for young people with TS. Larger controlled studies are, however, needed to determine the clinical efficacy of this format.
A perhaps related treatment delivery format, where a DVD is provided to the patient with instructions on how to perform HRT (with support of a parent), has been tested in a pilot randomized controlled trial (7–13 years; N = 44) . Both the DVD-HRT group and the comparison face-to-face-HRT group showed improvements on the YGTSS-TTS in a within-group analysis. Results are, however, difficult to interpret due to large dropout rates and the lack of an intention-to-treat analysis.
Internet delivery of BT
In internet-delivered BT, patients work through a self-help programme briefly supported by a therapist (via text messages or telephone). A Swedish internet platform called BIP (Barninternetprojektet [The Child Internet Project]) has successfully been used to deliver such internet-delivered treatment for several pediatric mental health conditions [57, 58]. Andrén et al. used the BIP-platform to evaluate two therapist-guided internet-delivered interventions based on HRT and ERP principles (called BIP TIC HRT and BIP TIC ERP) in a pilot trial (8–16 years; N = 23) . Both interventions showed a significant reduction in tic-related impairment and parent-rated tic severity, but only BIP TIC ERP showed a significant improvement in clinician-rated tic severity as assessed by the YGTSS-TTS (within-group effect sizes at the 3-month follow-up: BIP TIC ERP: 1.12; BIP TIC HRT: 0.50). Therapeutic gains were maintained at the 12-month follow-up. An additional advantage of the treatment format was that it demanded less therapist time (approximately an average of 25 min per participant per week, mainly via text messages) than traditional face-to-face BT.
In an Israeli RCT (7–18 years; N = 45) , Rachamim et al. compared internet-delivered CBIT to a waitlist condition. The results showed a large, significant between-group effect on the YGTSS-TTS (ηp2 = 0.20; in favor of internet-delivered CBIT). The active group was followed until 6 months post-treatment, where it showed a large within-group effect on the YGTSS-TTS (d = 2.25). Also in this study, therapists spent considerably less time with patients (ca. 7 min per participant per week, via telephone) than in traditional face-to-face BT.
Studies have explored the benefits of delivering treatment in an intensive and brief manner, potentially making treatment more efficient and convenient for patients who travel long distances to receive care. Blount et al. piloted an intensified version of the CBIT-protocol (several hours of daily treatment over a 4 day period, called IOP CBIT) in two boys (ages 10 and 14 years) with TS, showing a tic reduction which was maintained up to 6 and 7 months later . Along the same line, van de Griendt et al. addressed the question of whether shorter sessions of ERP (1 h compared to the 2 h used in the Verdellen et al. RCT ) would yield a different treatment outcome . Results suggest that shorter sessions were not inferior to longer sessions regarding tic severity outcomes, implicating the clinical use of shorter sessions to accommodate more treatment delivery within the same time frame . Chen et al. evaluated the effects of a shortened CBIT-protocol (four instead of eight sessions). In a RCT , 46 participants (6–18 years) were randomized to shortened CBIT plus usual care (psychoeducation and 50 mg of pyridoxine) or usual care only. Results showed a medium-sized, significant between-group effect on the YGTSS-TTS (in favor of CBIT plus usual care; d=0.56). The CBIT plus usual care-group further improved in a within-group analysis at a 3-month follow-up. This study provides preliminary evidence for CBIT being efficacious also in half of the previously evaluated dose. A final example of a shortened CBIT-protocol is the previously reported study by Bennett et al , where the treatment was shortened from 8 to 6 sessions for their very young sample (5–8 years), and still was shown to be efficacious. Another example of a more intensive treatment approach is the previously mentioned “Tackle your tics”-programme . Further studies are needed to evaluate the intensity, spacing and duration of treatment sessions on the efficiency and effectiveness of BT.