Although the cause of TS is unknown, current research points to abnormalities in certain brain regions (including the basal ganglia, frontal lobes, and cortex), the circuits that interconnect these regions, and the neurotransmitters (dopamine, serotonin, and norepinephrine) responsible for communication among nerve cells. Given the often complex presentation of TS, the cause of the disorder is likely to be equally complex.

Many with TS experience additional neurobehavioral problems including inattention; hyperactivity and impulsivity (attention deficit hyperactivity disorder—ADHD) and related problems with reading, writing, and arithmetic; and obsessive-compulsive symptoms such as intrusive thoughts/worries and repetitive behaviors. For example, worries about dirt and germs may be associated with repetitive hand-washing, and concerns about bad things happening may be associated with ritualistic behaviors such as counting, repeating, or ordering and arranging.  People with TS have also reported problems with depression or anxiety disorders, as well as other difficulties with living, that may or may not be directly related to TS.  Given the range of potential complications, people with TS are best served by receiving medical care that provides a comprehensive treatment plan.

Evidence from twin and family studies suggests that TS is an inherited disorder. Although early family studies suggested an autosomal dominant mode of inheritance (an autosomal dominant disorder is one in which only one copy of the defective gene, inherited from one parent, is necessary to produce the disorder), more recent studies suggest that the pattern of inheritance is much more complex.  Although there may be a few genes with substantial effects, it is also possible that many genes with smaller effects and environmental factors may play a role in the development of TS. Genetic studies also suggest that some forms of ADHD and OCD are genetically related to TS, but there is less evidence for a genetic relationship between TS and other neurobehavioral problems that commonly co-occur with TS. It is important for families to understand that genetic predisposition may not necessarily result in full-blown TS; instead, it may express itself as a milder tic disorder or as obsessive-compulsive behaviors. It is also possible that the gene-carrying offspring will not develop any TS symptoms.

The sex of the person also plays an important role in TS gene expression. At-risk males are more likely to have tics and at-risk females are more likely to have obsessive-compulsive symptoms.

People with TS may have genetic risks for other neurobehavioral disorders such as depression or substance abuse. Genetic counseling of individuals with TS should include a full review of all potentially hereditary conditions in the family.

Although there is no cure for TS, the condition in many individuals improves in the late teens and early 20s. As a result, some may actually become symptom-free or no longer need medication for tic suppression. Although the disorder is generally lifelong and chronic, it is not a degenerative condition. Individuals with TS have a normal life expectancy. TS does not impair intelligence. Although tic symptoms tend to decrease with age, it is possible that neurobehavioral disorders such as depression, panic attacks, mood swings, and antisocial behaviors can persist and cause impairment in adult life.

Although students with TS often function well in the regular classroom, ADHD, learning disabilities, obsessive-compulsive symptoms, and frequent tics can greatly interfere with academic performance or social adjustment. After a comprehensive assessment, students should be placed in an educational setting that meets their individual needs. Students may require tutoring, smaller or special classes, and in some cases special schools.

All students with TS need a tolerant and compassionate setting that both encourages them to work to their full potential and is flexible enough to accommodate their special needs. This setting may include a private study area, exams outside the regular classroom, or even oral exams when the child's symptoms interfere with his or her ability to write. Untimed testing reduces stress for students with TS.

Within the Federal government, the leading supporter of research on TS and other neurological disorders is the National Institute of Neurological Disorders and Stroke (NINDS). The NINDS, a part of the National Institutes of Health (NIH), is responsible for supporting and conducting research on the brain and central nervous system.

NINDS sponsors research on TS both in its laboratories at the NIH and through grants to major medical institutions across the country. The National Institute of Mental Health, the National Center for Research Resources, the National Institute of Child Health and Human Development, the National Institute on Drug Abuse, and the National Institute on Deafness and Other Communication Disorders also support research of relevance to TS. And another component of the Department of Health and Human Services, the Centers for Disease Control and Prevention, funds professional education programs as well as TS research.

Knowledge about TS comes from studies across a number of medical and scientific disciplines, including genetics, neuroimaging, neuropathology, clinical trials (medication and non-medication), epidemiology, neurophysiology, neuroimmunology, and descriptive/diagnostic clinical science.

Genetic studies. Currently, NIH-funded investigators are conducting a variety of large-scale genetic studies. Rapid advances in the technology of gene finding will allow for genome-wide screening approaches in TS, and finding a gene or genes for TS would be a major step toward understanding genetic risk factors. In addition, understanding the genetics of TS genes will strengthen clinical diagnosis, improve genetic counseling, lead to the clarification of pathophysiology, and provide clues for more effective therapies.

Neuroimaging studies. Within the past 5 years, advances in imaging technology and an increase in trained investigators have led to an increasing use of novel and powerful techniques to identify brain regions, circuitry, and neurochemical factors important in TS and related conditions.

Neuropathology.  Within the past 5 years, there has been an increase in the number and quality of donated postmortem brains from TS patients available for research purposes.  This increase, coupled with advances in neuropathological techniques, has led to initial findings with implications for neuroimaging studies and animal models of TS.

Clinical trials.  A number of clinical trials in TS have recently been completed or are currently underway.  These include studies of stimulant treatment of ADHD in TS and behavioral treatments for reducing tic severity in children and adults. Smaller trials of novel approaches to treatment such as dopamine agonist and GABAergic medications also show promise.

Epidemiology and clinical science. Careful epidemiological studies now estimate the prevalence of TS to be substantially higher than previously thought with a wider range of clinical severity. Furthermore, clinical studies are providing new findings regarding TS and co-existing conditions.  These include subtyping studies of TS and OCD, an examination of the link between ADHD and learning problems in children with TS, a new appreciation of sensory tics, and the role of co-existing disorders in rage attacks. One of the most important and controversial areas of TS science involves the relationship between TS and autoimmune brain injury associated with group A beta-hemolytic streptococcal infections or other infectious processes. There are a number of epidemiological and clinical investigations currently underway in this intriguing area.