Work is likely the last place an employee might go to seek help for depression, but employees who took part in a workplace intervention program had fewer symptoms and were far more productive, U.S. researchers said on Tuesday.

Depression has a huge personal cost, but it also costs U.S. companies -- to the tune of tens of billions of dollars by some estimates.

Researchers at the National Institute of Mental Health, writing in the Journal of the American Medical Association, suggest that investing in depression intervention programs can help both the workers and the company.

Dr. Ken Wells of the University of California, Los Angeles, who wrote an editorial in the same issue, said the study offers a compelling argument for investing in depression care.

There have been prior studies in the last four to five years that have shown the link between employment and recovery of employment and depression treatment, he said in a telephone interview.

This is the first study that really focuses exclusively on that story in the work force.

The study was led by Dr. Philip Wang of the National Institute of Mental Health. He and colleagues studied 604 workers with significant depression who were covered by behavioral health plans through their companies.

Half the workers were contacted through a telephone outreach program and encouraged to seek outpatient treatment -- therapy, antidepressants, or both.

Telephone support workers monitored quality of care and even made suggestions to clinicians when treatment was not working. Those reluctant to enter treatment were offered a therapy program over the phone.

The study found that workers in the telephone support group fared far better than those who got routine care. They had less severe depression and they were more likely to experience recovery. About 26 percent of workers in the intervention group recovered, compared with about 18 percent in the routine care group.

The program paid off for companies as well. Workers in the intervention group worked an average of two hours more per week over the course of a year -- or about two more weeks a year -- compared to those who got routine care.

Of course, the benefits of recovery extend far beyond the workplace. This touches many, many families, Wells said.

According to the World Health Organization, depression affects about 121 million people worldwide.

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