More than half of people with Tourette also have obsessive-compulsive disorder (OCD) or ADHD, and up to 20 percent have autism. Because all four conditions can involve impulsive and compulsive behaviors, some scientists have proposed that they exist along a spectrum, with ADHD on one end, OCD on the other, and autism and Tourette in the middle.
researchers analyzed data from previous studies that involved a total of 93,294 people with at least one of the four conditions, along with 51,311 controls. They looked at common variants — single-letter changes to DNA that appear in more than 1 percent of the population — shared by any two of the four conditions.
The newly identified variants tend to occur in genes that are highly expressed in the brain, the researchers found, including in the hypothalamus and the pituitary and adrenal glands. Together these regions form a system involved in the body’s response to stress that may function differently in people with autism, ADHD or Tourette syndrome.