Researchers Confirm Tourette Syndrome and Obsessive Compulsive Disorder are Heritable
Both Tourette syndrome (TS) and obsessive-compulsive disorder (OCD) have been well known mental health issues for a long time, but little is understood about what causes the diseases. They have been long been identified solely upon symptoms exhibited by patients, but researchers are finally beginning to understand the nature of these mental illnesses.
An international research consortium led by researchers from Massachusetts General Hospital (MGH) and the University of Chicago have finally uncovered some information regarding the genetic background of the two conditions, as well as providing the first clear confirmation that both are highly heritable. News-Medical reports they also made a major discovery by showing that there are major differences between the underlying genetic makeup of the disorders. Previously, the two conditions were believed to be closely related.
“Both TS and OCD appear to have a genetic architecture of many different genes – perhaps hundreds in each person – acting in concert to cause disease,” says Jeremiah Scharf, MD, PhD, of the Psychiatric and Neurodevelopmental Genetics Unit in the MGH Departments of Psychiatry and Neurology, senior corresponding author of the report. “By directly comparing and contrasting both disorders, we found that OCD heritability appears to be concentrated in particular chromosomes – particularly chromosome 15 – while TS heritability is spread across many different chromosomes.”
OCD is the fourth most common psychiatric illness, characterized by obsessions and compulsions which disrupt the lives of patients. TS, on the other hand, is a chronic disorder characterized by motor and vocal tics which normally begin in childhood. The two have long been linked because TS is often accompanied by OCD or attention-deficit hyperactivity disorder.
It has been suspected that both conditions were heritable, since both commonly recur in close relatives of those affected. However, it has been very difficult to identify the exact genes that confer risk.
“Trying to find a single causative gene for diseases with a complex genetic background is like looking for the proverbial needle in a haystack,” says Lea Davis, PhD, of the section of Genetic Medicine at the University of Chicago, co-corresponding author of the report, which will be published in PLOS Genetics. “With this approach, we aren’t looking for individual genes. By examining the properties of all genes that could contribute to TS or OCD at once, we’re actually testing the whole haystack and asking where we’re more likely to find the needles.”