**7. Conclusions**

Data from tics research prompt significant variations in prevalence. Future research should, at minimum, supplement indirect measures with direct methods. Nolan demonstrated that

Tics and vocalizations developing in later life in association with neuroacanthocytosis80, Sydenham's chorea and L-dopa–treated postencephalitic parkinsonian syndrome81. There

Chouinard and colleagues reported on 7 cases of idiopathic tic disorder that presented after the patients were 21 years of age75. Adult-onset tic disorder in the absence of any other

Adult-onset cases need to be evaluated using a wide screening, like the National Hospital Interview Schedule for the assessment of GTS and related behavior82; this is a standardized, semistructured instrument that includes systematic assessment of personal and family history of GTS, ADHD, and obsessive compulsive behavior (OCB). The interview is conducted with the patient and a family member (usually a parent) who knows the patient

Several cases of secondary tourettism have been described in the literature. The causes have included postencephalic syndrome and carbon monoxide intoxication, and other causes have been degenerative or vascular75. Tourettism has also occurred secondary to trauma83, infection84, alcohol withdrawal85, or intake of certain drugs such as stimulants, anticholinergics, or antipsychotics86 87. In almost all patients there was a potential trigger event, such as drug exposure, viral or bacterial infection, physical trauma, cerebrovascular disease, or psychiatric illness prior to the onset of tic symptomatology. These may have acted as a trigger to unmask the symptoms in a constitutionally predisposed individual. In this regard, it is interesting to note that in 50% of cases there is either a personal or family history of GTS-related behavior. However, it is also possible that these represented secondary tics. It is now recognized that GTS has a genetic cause, with some studies

Goetz and coworkers in a study of 58 adult GTS patients diagnosed during childhood observed that childhood tic severity had no predictive value and that coprolalia did not increase the risk for severe tics in adult life89. Features predictive of mild tics in adulthood were mild tics during the patients' worst preadulthood function and mild tics during adolescence. The phenomenology of tics encountered in later life may also be somewhat different from those in early-onset GTS. For example, it has been reported reduced response to treatment (31%), a high degree of social morbidity (89%) and a low frequency of spontaneous complete remission in adult-onset cases. It seems that adult-onset tic disorder, whether idiopathic, secondary or a

A majority of patients exhibit OCB in childhood and have a positive family history of tics or OCB. It may also be noted that childhood rheumatic chorea may resolve only to return in late adult life89. Linazasoro and colleagues described a patient who had presented with only OCD since childhood but developed GTS symptoms at the age of 72 years and suggested that the expression of the gene may be different in the same patient during the course of his life90.

Data from tics research prompt significant variations in prevalence. Future research should, at minimum, supplement indirect measures with direct methods. Nolan demonstrated that

are a few reports of isolated and spontaneous adult-onset tics disorders.

primary neurological disorder has onset of tic symptoms from 23 to 52 years76.

suggesting an autosomal dominant transmission and others a mixed model88.

recurrence of childhood tics, may be different from younger-onset GTS.

**7. Conclusions** 

**6.2 Adults with tics and comorbidities** 

well enough to give relevant details about childhood.

correspondence between direct observation scores and YGTSS ratings may be lower for lowfrequency tics than for high-frequency tics91.

Whether tic frequency is the most important dimension of tic severity (*e.g.* best predicts psychosocial functioning) is an empirical issue that warrants investigation. Studies should evaluate methods capable of quantifying multiple dimensions of tics including overt physical dimensions (*e.g.* frequency, intensity, complexity), social dimensions (*e.g.* social reinforcement and punishment contingencies, functional interference) and the concomitant private dimensions commonly reported to accompany tics (*e.g.* sensory events). The research will likely require novel direct observation techniques used in combination with other measurement methods (*e.g.* functional assessment, self-report, clinician ratings, social acceptability ratings, physiological measures, neuroimaging techniques, etc.) and research strategies (*e.g.* functional analysis, group research designs, inferential statistical analyses).

The use of not traditional measurement techniques to complement direct observation is likely to increase in popularity within the broader field of clinical behavior analysis. Clinical researchers are increasingly concerning themselves with the study of behavior that is complex, highly variable and not easily accessible by traditional direct-observation techniques (*e.g.* the private behaviors of individuals who suffer from anxiety and mood disorders). If behavior analysts are to continue to be at the forefront for understanding and treating clinical problems (including tic disorders), they must systematically determine which dimensions of specific target behaviors are socially relevant and must be diligent not to restrict themselves by investigating only those aspects that are easily quantifiable with traditional direct observation methods92. This will require researchers both to refine their current measurement techniques and to incorporate techniques that have not traditionally been employed in behavior-analytic research (*e.g.* clinician ratings, self-report, physiological and neuroimaging techniques, etc). This is not to suggest that clinical behavior analysts abandon direct observation in favor of other measurement techniques. On the contrary, it is a call to behavior analysts to develop, investigate and incorporate new direct and indirect measurement techniques that will enhance scientific investigation of the environment– behavior relations involved in clinical problems.
