ARTICLE IN BRIEF
One of the largest and most comprehensive studies of people with Tourette syndrome to date found that the lifetime prevalence of any psychiatric comorbidity was 85.7 percent, with 72.1 percent meeting the criteria for obsessive-compulsive disorder or attention-deficit/hyperactivity disorder.
The largest and most comprehensive study to date of people with Tourette syndrome (TS) has found that the vast majority have at least one psychiatric comorbidity during their lifetime, with most of them meeting the criteria for obsessive-compulsive disorder (OCD) or attention-deficit/hyperactivity disorder (ADHD).
The findings, while not surprising to neurologists who specialize in the syndrome, highlight the need for clinicians to identify psychiatric comorbidities and see that they are treated when appropriate, either directly or by a collaborating psychiatrist.
“This study is largely confirmatory,” said Jonathan W. Mink, MD, PhD, FAAN, chief of child neurology and vice chair of neurology at the University of Rochester Medical Center in New York, where he is director of its comprehensive Tourette syndrome clinic. “It should emphasize to neurologists that when you see a patient who presents with tics as the presenting complaint, it is critically important to make sure the evaluation includes a careful history about anxiety, depression, OCD, impulsivity, and distractibility — all those symptoms that are common.” Dr. Mink was not involved with the study.
Because previous, smaller studies had found prevalence rates of psychiatric comorbidities among TS patients ranging from a low of 61 percent to a high of 96 percent, the new study in JAMA Psychiatry sought to bring greater precision through structured diagnostic interviews with 1,374 patients and 1,142 unaffected family members.
Conducted by an international group of researchers known as the Tourette Syndrome Association International Consortium for Genetics, the trial primarily recruited patients from tic specialty clinics in the United States, Canada, Great Britain, and the Netherlands, as well as from the Tourette Syndrome Association of the United States. Phenotypic data were collected from genetic studies, and interviews were conducted between April 1, 1992, and Dec. 31, 2008. The mean age of the patients at assessment was 19.1 years.
The lifetime prevalence of any psychiatric comorbidity among the patients was 85.7 percent, with 72.1 percent meeting the criteria for OCD or ADHD. Over half of the patients (57.7 percent) had two or more psychiatric disorders. Aside from OCD and ADHD, other disorders — including mood, anxiety, and disruptive behavior disorders — occurred in approximately 30 percent of participants, the study found.
The age of greatest risk for the onset of most comorbid disorders was between four and 10 years, with the exception of eating and substance use disorders, which began in adolescence.
“The take-home message is that you've got to continually ask about OCD, ADHD, and these other comorbidities whenever you see the patient, whether they're six or eight or 10 years old, or even older,” said Harvey S. Singer, MD, FAAN, a professor of neurology and pediatrics at Johns Hopkins University School of Medicine in Baltimore, MD, who was not involved with the study.
While TS was associated with a moderately increased risk of anxiety (odds ratio 1.4; 95% CI 1.0-1.9), the risk of substance use disorders was actually decreased after controlling for the effects of comorbid OCD and ADHD. For those who did have OCD, the risk of mood disorders was 3.7 times higher than for those who did not have OCD.
In addition, high tic severity was associated with an increased risk of non-ADHD and non-OCD comorbidities.
The results, the study concluded, “suggest that psychiatric assessments of TS-affected children should begin early and continue throughout adolescence and adulthood.”
“Our results also suggest that TS-affected children who have concomitant OCD or a parent with ADHD should be carefully evaluated over time for the development of mood disorder, anxiety disorder, and DBD [disruptive behavior disorder],” the authors continued. “In addition, adolescents, particularly those with OCD and/or ADHD, should be monitored for the development of a substance use disorder.”
Etiologically, the study provided the first evidence of a strong genetic relationship between TS-related phenotypes and mood, anxiety, and disruptive behavior disorders. “Of particular interest,” the study noted, “our analyses suggest that the observed genetic correlations between TS and these disorders are better accounted for by an underlying genetic relationship with ADHD and, in the case of mood disorders, by an underlying genetic relationship with both ADHD and OCD.”
Both because the participants were drawn from clinics specializing in TS and had a relatively mature age at assessment, the findings might present a more severe picture of tic disorders than that seen by general neurologists, said Joseph Jankovic, MD, FAAN, a professor of neurology and director of the Parkinson's Disease Center and Movement Disorders Clinic at Baylor College of Medicine in Houston.
“Their population may be a little more severe than that of the general population,” he told Neurology Today. “In our clinic, though, I would expect the rates of OCD and ADHD to be even higher, as we are a tertiary referral center for Tourette syndrome.”
Dr. Mink agreed. “One of the things we know about tics is that for many individuals, their symptoms improve and may even go away by the time they become adults,” he said. “So there may be an over-representation in this study of those for whom the tics persist, and those people might be more likely to have the psychiatric comorbidities.”
Even while acknowledging the high prevalence of psychiatric comorbidities, Dr. Jankovic emphasized that “Tourette syndrome is a neurologic disorder. It's not a psychiatric disorder. The appropriate home for patients with TS is a neurology clinic. It's true that the majority of patients have a variety of psychiatric comorbidities, but that's also true of many patients with movement disorders.”
TS patients who are initially referred to a psychiatrist sometimes receive treatment for their comorbidities without regard to their neurologic symptoms, Dr. Jankovic said. “If the patient has ADHD, a psychiatrist might put the patient on a central nervous system stimulant, which can make the tics worse,” he said. “The treatment of tics should come first.”
Most movement disorder neurologists should be skilled in recognizing and treating the psychiatric comorbidities of TS, Dr. Jankovic said. When referral to a psychiatrist is warranted, “the psychiatrist and the neurologist need to work together,” he said.
Dr. Mink agreed. “Some neurologists are quite competent in caring for the full range of symptoms, and that includes a number of movement disorder neurologists,” he said. “For other neurologists, it may be important to have the active, collaborative involvement of a psychiatrist.”
Behavioralists are also increasingly being included as part of the treatment team, Dr. Mink said. “We're in the middle of a major paradigm shift, away from medications being the first-line treatment and toward behavioral treatments. A form of behavioral therapy called habit reversal therapy has been shown to be highly effective. Increasingly, neurologists and psychiatrists are referring patients for behavioral interventions as a first-line treatment for tic disorders.”
Before either medications or behavioral treatments, Dr. Mink said, “The first line of treatment for any child or adult with a new diagnosis of a tic disorder is education and reassurance. The great majority of people with TS lead happy, healthy, productive lives. This is a disorder that is not degenerative and is not expected to get worse over the lifespan. And no further treatment is necessary unless the symptoms are bothersome.”