Tourette Disorder

Tourette and other chronic tic disorders are neurodevelopmental/neuropsychiatric disorders characterized by motor and/or vocal tics that make their appearance before the age of 18 years. While the diagnostic criteria for Tourette disorder (TD) require the presence of multiple motor and at least one vocal tic over at least 1 year, the criteria for chronic motor tic (CMTD) or chronic vocal tic (CVTD) disorders require at least 1 year of having either motor or vocal tics, respectively, but not both, during the individual’s lifetime. Tic severity symptoms characteristically wax and wane throughout the day, weeks, months, and years. The lifetime prevalence of TD ranges from 0.32 to 0.85%, and combined, the prevalence CI of all chronic tic disorders (CTDs) ranges from 0.92 to 2.83%.

Individuals with TD and their family members frequently exhibit comorbid difficulties such as obsessions and compulsions (including full-blown OCD); Attention Deficit Hyperactivity Disorder (ADHD); and a vulnerability to anxiety and depression. Family, segregation and twin studies consistently indicate that genetic factors play a significant role in the etiology of TD and suggest that obsessive-compulsive symptoms (or OCD) may be an alternative manifestation of the gene. Although there have been some initial positive findings, identification of replicable susceptibility alleles has thus far remained elusive.

In 2007, Dr. Heiman and others established the New Jersey Center for Tourette Syndrome (NJCTS) Sharing Repository, a sharing resource of clinical, biomaterial, and genetic data of Tourette individuals and their families. Using the NJCTS Repository as pilot data, they received funding from the National Institutes of Health (NIH) in 2011 to extend this sharing repository worldwide- called the Tourette International Collaborative Genetics (TIC Genetics) group. TIC Genetics brings together a team of clinicians, geneticists, and statistical geneticists from 24 sites across the US, Europe, and South Korea and is now the largest sharing cell and DNA repository for Tourette syndrome (TS). Dr. Heiman serves on the TIC Genetics Executive Committee, heads the Data Coordinating Center, co-leads the Phenotyping Assessment Committee, and directs the Rutgers recruitment site. In 2018, TIC Genetics received another NIH grant to continue this work for an additional 5 years. The goal of these repositories is to identify genetic factors that play a role in causing TS and comorbid disorders such as Obsessive-Compulsive Disorder (OCD) and Attention-Deficit/Hyperactivity Disorder (ADHD).

Recently, the TIC Genetics group published two scientific articles in which they identified damaged, “high confidence” TS risk genes. Interestingly, some of these risk-raising genes are involved in “cell polarity” which suggests that cell polarity might be a mechanism in causing TS. A disruption in cell polarity could affect how neurons are getting to the correct location and making connections during neurodevelopment. TIC Genetics estimates that there are over 400 genes that, when mutated, could each pose a risk for TS. These breakthrough findings suggest that TS, like other neuropsychiatric disorders, is the result of multiple gene mutations.