• Science Update
Co-occurring attention deficit hyperactivity disorder (ADHD) may be at the root of attention problems in children with Tourette syndrome (TS), according to NIMH-funded researchers. Their findings also support the theory that children with TS develop different patterns of brain activity in order to function at the same level as children without TS. The study was published in the November 2010 issue of the Journal of the American Academy of Child & Adolescent Psychiatry.
Tourette syndrome is a chronic neurological disorder associated with repetitive, involuntary movements and vocalizations called tics. Many with TS also experience neurobehavioral problems such as inattention, hyperactivity, and impulsivity—symptoms that overlap with ADHD. In fact, researchers estimate that between 50-90 percent of youth with TS also have ADHD.
To explore the role of co-occurring ADHD in TS, Denis Sukhodolsky, Ph.D., of the Yale Child Study Center, and colleagues studied 236 children, of which:
- 56 had TS only
- 64 had ADHD only
- 45 had TS+ADHD
- 71 had neither and served as a comparison group.
The researchers used well-known, standardized measures to evaluate the children's performance on tasks requiring:
- Sustained attention and inhibitory control—Participants were shown various letters on a computer screen and told to press a button when they saw certain letters but not press the button when they saw a non-target letter.
- Cognitive inhibition—Participants were shown an array of dots on sheets of paper and asked to name their color (red, green, blue) as quickly as possible. In related tasks, participants were shown pages with similarly arrayed words ("red," "green," "blue") printed in black ink or a mismatched color of ink (such as "red" printed in green ink) and asked to read the words as quickly as possible.
- Fine motor control—Participants placed small pegs in a specially designed pegboard in 30-second trials using only their dominant hand, only their non-dominant hand, and both hands at the same time.
- Visual-motor integration—Participants copied 24 geometric designs, presented in order of increasing difficulty.
Results of the Study
Children with TS+ADHD showed similar problems with sustained attention as children with ADHD only. However, unlike those with ADHD only, children with TS+ADHD performed at the same level as the comparison group on all other tasks.
Children with TS only performed at the same level as the comparison group in tasks involving response inhibition and visual-motor integration. They performed at a slightly lower level than comparison children on the fine motor control task. Girls with TS only scored higher than boys with TS only on fine motor control tasks using their dominant hands.
The study helps to identify brain functions specific to particular disorders and the mechanisms underlying these functions.
Similarities in performance between children with TS+ADHD and those with ADHD only suggest that co-occurring ADHD may underlie attention problems in children who have TS, according to the researchers.
The researchers also noted that the children with TS only didn't show impairment in response inhibition, lending support to a theory that such children develop compensatory brain mechanisms in an effort to control involuntary tics. Past imaging studies have shown that, during tasks involving response inhibition, children with TS have greater than normal activity in brain areas associated with cognitive control.
Differences in fine motor skills between girls and boys with TS may indicate differing developmental pathways and patterns of brain growth between the sexes. Because problems with fine motor control in childhood are associated with more severe tics in adulthood, the researchers highlighted this finding as an area for further study.
Future studies may help advance the understanding of how TS arises and changes in brain growth and functioning that are associated with the disorder.
Sukhodolsky DG, Landeros-Weisenberger A, Scahill L, Leckman JF, Schultz RT. Neuropsychological functioning in children with Tourette syndrome with and without attention-deficit/hyperactivity disorder . J Am Acad Child Adolesc Psychiatry. 2010 Nov;49(11):1155-64.