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People with Tourette syndrome or chronic tic disorder were more likely than others to be violently assaulted or convicted of a crime, a cohort study in Sweden showed.

Compared with the general population, people diagnosed with Tourette syndrome or chronic tic disorder had a two-fold increased risk of experiencing violent assault, a three-fold increased risk of violent crime convictions, and a 1.6-fold increased risk of nonviolent crime convictions, reported David Mataix-Cols, PhD, of the Karolinska Institutet in Stockholm, and co-authors.

More than a third of people with Tourette syndrome or chronic tic disorder (37.0%) who had experienced violent assault also had a violent crime conviction, the researchers wrote in .

However, most people with Tourette syndrome or chronic tic disorder were neither assaulted nor convicted of a crime, they added.

Tic disorders continue to be associated with significant social stigma, observed Davide Martino, MD, PhD, of the University of Calgary in Canada, and co-authors in an . Socially inappropriate behaviors, explosive or rage outbursts, imitative behavior, and forced touching can trigger serious reactions in bystanders, they noted.

"Many of our colleagues overseeing tic disorder specialty clinics have anecdotally encountered patients with tic disorders who have both experienced violent assault and perpetrated criminal behavior," they wrote. "However, it is unknown how prevalent these issues truly are as well as whether social stigma may contribute to -- and at times drive -- these behaviors."

Mataix-Cols and co-authors have "convincingly documented that individuals with Tourette syndrome are significantly more likely not only to experience assault but also to be perpetrators of violent (including sexual) assaults," the editorialists continued. "These topics have been considered taboo, and thus, there has been hesitancy to open a Pandora's box, which may further drive negative public impressions of individuals with Tourette syndrome and related conditions."

"However, we argue that it is vitally important to collect data, understand potential issues, and design and implement meaningful interventions," they pointed out. "If we fail to adequately understand and address these issues, we may be missing a huge opportunity to improve the quality of life for many individuals and families dealing with Tourette syndrome or a persistent tic disorder."

The study assessed records of 13.8 million individuals living in Sweden from 1973 to 2013, including 7,791 people who received a diagnosis of Tourette syndrome or chronic tic disorder from a specialist. Median age was 13.4 at first diagnosis, and 76% were male. Most had at least one comorbid psychiatric disorder.

Median follow-up was 29.9 years for violent assault outcomes and 18.4 years for crime conviction. Findings were adjusted for sex and birth year.

The risk of experiencing violent assault was more than twice as high among people with Tourette syndrome or chronic tic disorder (adjusted HR 2.21, 95% CI 2.00-2.43). The cumulative incidence of experiencing any violent assault was 14% by the end of follow-up at age 41, compared with 5% in the general population.

Violent crime convictions were more than three times as high in people with Tourette syndrome or chronic tic disorder (adjusted HR 3.13, 95% CI 2.92-3.36). The risk of violent crime convictions was higher in women. Cumulative incidence showed that 22% of people with Tourette syndrome or chronic tic disorder had a violent crime conviction by the age 41, compared with 5% in the general population.

Risk of convictions for nonviolent offenses was also higher in people with Tourette syndrome or chronic tic disorder (adjusted HR 1.62, 95% CI 1.54-1.71). Cumulative incidence showed that 39% had a conviction for nonviolent crime by age 41, versus 18% in the general population.

Overall, risks were highest in individuals with comorbid attention deficit-hyperactivity disorder (ADHD) and substance use disorders. Excluding these people partly weakened the associations, as did within-sibling models.

The study had several limitations, Mataix-Cols and colleagues acknowledged. It assessed only people who had been diagnosed by a specialist and results may not apply to people with mild tic disorders. Violent assaults were serious events requiring medical care; unreported forms of assault or crimes that did not result in convictions were not included. The researchers also did not have information about tic symptom severity.

"Undoubtedly, the findings presented in this article will generate a lively debate," the editorialists wrote. "Concerns will be raised about the risk of reinforcing the social stigma of individuals with Tourette syndrome or persistent tic disorder."

"However, if this debate appropriately focuses on the objective and accurate interpretation of the data, it will provide an opportunity for the field to recognize and to address these realities," they added.

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