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Commercial Data Yield Genetic Links to Depression

Worried woman

(Ryan McGuire, Pixabay)

2 August 2016. An analysis of data from commercial genetic tests identified 15 regions in the genome and 17 specific variations associated with depression among people of European descent. The team from Massachusetts General Hospital in Boston and the personal genetics testing company 23andMe reported its findings in yesterday’s issue of the journal Nature Genetics (paid subscription required).

The team, funded by National Institute of Mental Health and led by Mass. General psychiatric geneticist Roy Perlis, sought to pinpoint genetic factors behind depression, a disorder affecting 7.6 percent of the U.S. population age 12 and over in any 2-week period. Centers for Disease Control and Prevention says major depressive disorder, also known as clinical depression, resulted in 8 million visits to U.S. doctor’s offices or hospitals, in 2009-2010.

To identify these genetic factors, Perlis and colleagues needed data from hundreds of thousands of individuals to generate statistically reliable findings, a near-insurmountable task with traditional recruitment methods. Samples this large are needed due to the complex nature of depression and many subtle forms the disorder can take.

Instead, the team gained the cooperation of 23andMe in Mountain View, California, which offers personal genetic testing services for as low as $99.00. The company also asks its customers to volunteer their data for research of this kind, and complete questionnaires where participants give their medical histories, including psychiatric illnesses.

From the database of volunteer genomes, where identifying information is removed, the researchers analyzed common genetic variations in 75,607 individuals of European origin, who reported a diagnosis or treatment for depression. For comparison, the team analyzed data from 231,747 persons also of European heritage, with no reports of depression.

In addition, the researchers integrated the data from 23andMe with an earlier genome-wide association study by the Psychiatric Genomics Consortium, adding data from more than 20,000 individuals of European ancestry, both people with depression and healthy individuals for comparison, whose conditions were verified by clinicians. The team then more closely analyzed regions in the genome with possible depression associations among 45,773 people in the 23andMe database reporting the disorder, and 106,354 individuals without the controls.

The results from all 3 data sets identified 15 regions in the genome showing a reliable statistical association with a diagnosis of depression. The analysis also revealed 17 independent genetic variations called single nucleotide polymorphisms or SNPs revealing a reliable association with depression. SNPs are differences in nucleotides, the DNA base building blocks identified by the letters A, C, G, and T. Most SNPs occur normally in the genetic code, but some of these variations are associated with inherited disorders.

The authors believe the accumulated data collected by commercial genetic testing services like 23andMe offer a valuable resource to find new treatment strategies for depression. “The neurotransmitter-based models we are currently using to treat depression are more than 40 years old, and we really need new treatment targets,” says Perlis in a Mass. General statement.  He notes that a “key takeaway from our study is that the traditional way of doing genetic studies is not the only way that works. Using existing large data sets or biobanks may be far more efficient and may be helpful for other psychiatric disorders, such as anxiety disorders, where traditional approaches also have not been successful.”

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