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What: Researchers are beginning to probe the underlying genetic basis of obsessive compulsive disorder (OCD) and Tourette syndrome (TS), two neuropsychiatric disorders that frequently co-occur in families. A paper appearing this week in , led by Medical and Population Genetics and Stanley Center affiliate member Jeremiah Scharf, along with Ó³»­´«Ã½ associate member Ben Neale, confirms that both disorders are highly heritable and have distinct underlying genetic architecture (the number, frequency, and distribution of genetic risk factors).

The work demonstrates that the vast majority of TS and OCD heritability is captured by the results of genome-wide association studies (GWAS) – studies of thousands of individuals and the many common genetic variants their genomes harbor.

"This is a crucial point for genetic researchers, as there has been a lot of controversy in human genetics about what is called 'missing heritability'," said Scharf, a co-senior author of the study. "For many diseases, definitive genome-wide significant variants account for only a minute fraction of overall heritability, raising questions by GWAS critics about the validity of the approach. Our findings, similar to those found for other complex trait disorders, demonstrate that the vast majority of genetic susceptibility to TS and OCD can be discovered using GWAS methods. In fact, the degree of heritability captured by GWAS variants is higher for TS and OCD than for any other complex trait studied to date."

Who: A team of scientists from the Ó³»­´«Ã½, Massachusetts General Hospital, and the University of Chicago. Contributors with Ó³»­´«Ã½ affiliations include Dongmei Yu, Neale, and Scharf.

Why: Studies of twins and families have suggested that genetics may be important in the risk of developing TS or OCD, but previous efforts to pinpoint these genetic risk factors have been unsuccessful. This study offers insights that could help researchers determine the precise genetic risk factors for TS and OCD and, through studies in even larger patient populations, identify potential targets for drugs to treat the disorders.

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