WEDNESDAY, June 17, 2015 (HealthDay News) -- People who have a relative with Tourette syndrome or a tic disorder are at increased risk for the same condition, a new study says.
The highest risk is among first-degree relatives, such as siblings, parents and children, the researchers said.
Tourette syndrome is a nervous system condition marked by tics, or sudden twitches, movements or sounds, that people do repeatedly, according to the U.S. Centers for Disease Control and Prevention. It's estimated that one out of 360 U.S. children is diagnosed with the condition.
The researchers analyzed data from more than 4,800 people in Sweden diagnosed with Tourette syndrome and chronic tic disorder between 1969 and 2009.
First-degree relatives of people with these tic disorders had a much higher risk of the disorders than second- and third-degree relatives, whose risk was higher than people who did not have relatives with a tic disorder.
For example, first cousins of people with a tic disorder had a threefold higher risk than people who did not have relatives with a tic disorder, the researchers said.
The study was published online June 17 in the journal JAMA Psychiatry.
The findings show that genetics play a strong role in the risk for tic disorders, according to study author David Mataix-Cols, of the Karolinska Institute in Stockholm, and colleagues.
"The heritability of tic disorders was estimated to be approximately 77 percent, with the remaining variance being attributable to nonshared environmental influences and measurement error... Our heritability estimates place tic disorders among the most heritable neuropsychiatric conditions," they concluded.
The U.S. Centers for Disease Control and Prevention has more about Tourette syndrome.