Depression costs China at least 30 billion yuan (US$3.6 billion) in lost productivity a year, in a country where the problem is often ignored and treatment is underfunded, according to a study released on Friday.

The cost is particularly heavy for caregivers, who spend 17-25 percent of their annual salary and about 17 hours a week taking care of the depressed, according to the first-ever study of the phenomenon in China by international advocacy group the Social and Economic Burden of Depression (SEBOD).

The study also found that suicides attributable to depression cost China 5 billion yuan a year, with about 40 percent of all suicides the result of the illness.

It said China also ranks relatively low in terms of spending on depression, with about 3 percent of annual health care dollars going to the illness. By comparison, depression cases account for 8 percent of the country’s disability burden.

The relatively low spending on depression stems from a number of factors, said Martin Knapp, a professor of health economics at the London School of Economics.

“One problem is that people are not willing to recognize that there is a depressive disorder, either because of shame or reluctance to admitting to having a health problem,” he said. “So there’s a low referral rate.”

“Secondly, mental disorders are not given the same priority by the health care system.”

In conducting the study, SEBOD interviewed 500 patients diagnosed with depression in five of China’s largest cities.

“Similar to studies in other countries, indirect costs of depression in China are almost twice the costs of treatment,” said Teh-wei Hu, a professor of health economics and designer of the study.