According to new research from Yale University, a gene called MKP-1 may be responsible for causing the onset of depression.

The emotional disorder afflicts approximately 16 percent of Americans each year and costs more than $100 billion. Symptoms vary widely among individuals, and research suggests that there are multiple processes involved in the development of depression. This could explain why people often respond differently to the most commonly prescribed antidepressants.

Researchers found that the MKP-1 gene appeared to be more common in the brain tissues of adolescents with depression, compared to individuals in the control group.

In a mouse model, they discovered that when this gene was inactivated, the animals became resilient to stress. However, when it was allowed to be expressed normally, the mice exhibited symptoms that mimicked depression.

"This could be a primary cause, or at least a major contributing factor, to the signaling abnormalities that lead to depression," the scientists concluded.

The study, which was funded by the U.S. Health Service and the Connecticut Mental Health Center, may provide a target for therapy in those who suffer from the disorder.

According to PBS, approximately 4 percent of adolescents develop serious depression each year.