Exposure with response prevention versus habit reversal in Tourettes’s syndrome: a controlled study
Introduction
Tourette’s syndrome (TS) is a neuropsychiatric disorder characterized by multiple motor and vocal tics. Tics are sudden, rapid, recurrent, nonrhythmic, stereotyped movements or vocalizations that are experienced as irresistible but can be suppressed for varying lengths of time (American Psychiatric Association, 1994). Tics and TS related impulsive behaviours can be provoked by both external and internal events (Eapen, Moriarty and Robertson, 1994, Leckman, King and Cohen, 1999). Bliss (1980) had described unpleasant sensory experiences that precede tics, and that can be relieved by performing the tic. This description has challenged the commonly held belief that tics are involuntary. Several studies addressing the phenomenon of premonitory sensations and the intentional nature of tics have been performed thereafter (see Scahill, Leckman, & Marek, 1995, for a review). In tic-disordered patients, over 90% of tics seem to be preceded by unpleasant sensations and urges in contrast to 7% of patients with other movement disorders (Lang, 1991, Leckman, Walker and Cohen, 1993). In general, performance of tics relieves these sensations. In addition, there seems to be a strong relationship between the experience of premonitory sensations and the ability to suppress tics (Kurlan, Lichter, & Hewitt, 1989).
Whereas a biological basis for TS and its associated phenomena is generally assumed, insight into the functional maintenance of tics may be provided by learning theory (Turpin, 1983). Through a process of operant conditioning, i.e. negative reinforcement, the sequence of unpleasant premonitory sensations followed by tics that relieve these sensations may account for the maintenance of tics. Due to their potential to eliminate unpleasant sensory stimuli, tics can be considered as conditioned responses that will be performed whenever a new sensation appears. In addition, through classical conditioning, different kinds of stimuli (i.e. cognitive, emotional, and external) may become associated with the sensory stimuli and ticcing responses.
Derived from learning theory principles, interventions have been developed aimed at interrupting the stimulus-response sequences. To date, the hallmark of behavioural interventions for tics is habit reversal (HR). HR is based on the premise that tics are maintained by response chaining, lack of awareness of their occurrence, excessive practice, social reinforcement and tolerance of the tics (Azrin & Nunn, 1973). The primary ingredients of HR are an awareness training on the occurrence of a specific tic, and subsequently the application of a response incompatible with the tic, to interrupt or inhibit the tic (Miltenberger, Fuqua and McKinley, 1985, Peterson and Azrin, 1992). In addition, HR may comprise relaxation and reinforcement techniques (Azrin and Nunn, 1973, Peterson and Azrin, 1992). By applying HR, tic reductions between 55% and 95% have been reported (Peterson & Azrin, 1993).
Derived from the well-known repertoire of behavioural techniques, a new strategy for tics has been developed as an extension to HR, i.e. exposure and response prevention (ER; Hoogduin, Verdellen, & Cath, 1997). ER entails exposure to the sensations and urges that precede tics, and response prevention of the tics. Theoretically, the patient habituates to the premonitory experiences, thus resulting in tic reduction (Hoogduin et al., 1997). ER has proven to be effective in the treatment of obsessive–compulsive disorder (OCD; Abramowitz, 1996, Riggs and Foa, 1993). Tics in TS bear similarities with compulsions seen in OCD with regard to their intentional character (Cath, Spinhoven, Woerkom, Van, Wetering, Vande, Hoogduin, Landman and Roos, 2001, Lang, 1991, Turpin, 1983). In OCD, prolonged exposure to feared stimuli by means of ER results in decrements of both subjective anxiety and heart rate (Grayson, Foa and Steketee, 1982, Marks, 1987). In one report of a TS patient to whom ER has been applied, improvement of voluntary tic control and relief from the premonitory itching sensation has been demonstrated (Bullen & Hemsley, 1983). Hoogduin et al. (1997) have tested the habituation hypothesis in TS patients during ten 2-h sessions, in which the patients were exposed to the sensory experiences while suppressing every tic or impulse. Within-session habituation was found in three of the four patients. Improvements in ticcing behaviour varied from 68% to 83% (Hoogduin et al., 1997).
Studies on HR are in most cases uncontrolled, containing small sample sizes and poorly defined diagnostic criteria. The aim of the present study was to perform a controlled study, extending the preliminary data on ER in TS, using larger sample sizes, and in comparison with HR. The first hypothesis was that both ER and HR are effective in reducing TS tic symptoms, although the effect is possibly accomplished by different pathways of stimulus-response interruption in both techniques (Azrin and Peterson, 1990, Hoogduin, Verdellen and Cath, 1997). The second hypothesis was that ER results in larger tic symptom reductions than HR, since ER is directed towards disrupting the response sequence for all tics at once, whereas HR intervention focuses at one tic at a time. In addition, ER is applied to intervene in the response sequence as early as possible, i.e. immediately following the premonitory sensation. Early sequence interruption is associated with larger (and less effortful) behaviour change than disrupting the response sequence in the middle (Baumeister, Heatherton, & Tice, 1994).
Section snippets
Patients
Patients were referred for this study by the National TS Foundation and by psychiatrists and neurologists from various outpatient services. For inclusion in the study, the patients had to meet DSM-IV criteria (APA, 1994) for Tourette’s disorder. Exclusion criteria were major depression, psychotic disorder, autism, mental retardation and the presence of a neurological disorder other than TS. The use of medication during treatment was not considered an exclusion criterion, provided it was adhered
Results
High levels of interrater reliability were obtained for the YGTSS (r=0.98) and for TF-institute scores (r=0.99).
No significant differences were found between the groups on any of the patient characteristics or pre-treatment TS severity scores (Table 1).
Two patients from the ER condition (10%) and four patients from the HR condition (18%) did not complete the study. One patient dropped out after the first ER training session for unknown reasons. Five other patients dropped out after having
Discussion
The main conclusion from this study is that both ER and HR are effective interventions in the treatment of tics in TS. These results support our hypothesis and are in line with the literature (Azrin and Peterson, 1990, Hoogduin, Verdellen and Cath, 1997). Patients in both conditions showed significant reductions at the YGTSS and tic frequency outcome measures analysed simultaneously (p<0.0001). The results were comparable for the intent-to-treat sample.
To our knowledge, this is the first
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