An enormous study designed to uncover the genes involved in depression has left an international team of scientists somewhat empty-handed.
The research involved the DNA analysis of 34,549 volunteers as 86 scientists tried to pinpoint the genetic influences tied to depression.
“I’m disappointed,” said study coauthor Henning Tiemeier, M.D., Ph.D., of Erasmus Medical Center in Rotterdam, Netherlands. The lack of results “tells us that we have to be very modest,” he said. “Yet we think it’s doable to find some of the genes involved.”
Since depression runs in families, many experts believe that certain genes are partially responsible for the disorder. But research focused on individuals diagnosed with depression has failed to uncover these genes.
The new study focused solely on symptoms of depression, unlike earlier studies which focused more on diagnoses. Researchers integrated the results of 17 studies in which volunteers were given the same set of 20 questions regarding their emotional health at the time of the questionnaire.
An individual with many symptoms of depression received a high score, while a person with only a few symptoms scored low. The scientists reasoned that looking at a range of symptoms — instead of a black-and-white depression diagnosis — would be a better way to highlight the genes involved in depression.
Unfortunately, the method turned up nothing. The initial results showed zero genetic factors associated with depressive symptoms. Incorporating even more participants from studies that used other measures of depression didn’t help either. After raising the number of study subjects to 51,258, only one spot in the whole genome was tied to depressive symptoms, and that spot wasn’t close to any genes.
Despite the lack of results, the study raises an important question, said psychiatrist Dr. Steven Hamilton of Kaiser Permanente San Francisco Medical Center. “It was great that it was published,” because the study answered whether sliding scales of symptoms could be a successful way to study depression.
“It was a very reasonable hypothesis, and people were interested in it,” said Hamilton, formerly of the University of California, San Francisco.
Although somewhat controversial, many scientists believe that larger studies could still reveal a genetic basis for depression. And Tiemeier and his colleagues are determined, already planning a larger study that includes patients with depression diagnoses. “To be negative and to give up is far too early,” he said.
Source: Biological Psychiatry