The burden of mental illness in China has been seriously underestimated, the authors of a new study say. More than 17 percent of Chinese adults have a mental disorder, the study concluded — far more than the 1 to 9 percent reported in studies done between 1982 and 2004.

To do the study, published in the journal Lancet last week, researchers at Columbia University and major psychiatric hospitals in Beijing, Shandong, Zhejiang, Qinghai and Gansu screened 63,000 adults with questionnaires, and psychiatrists interviewed more than 16,000 of them, often in local dialects. The research was financed by the World Health Organization, the Shandong provincial health department and the China Medical Board of New York, an independent medical foundation begun in 1914 by the Rockefeller Foundation, which supports medical education and research across Asia.

The most disturbing aspect of their research, the authors said, was that, among those who had a diagnosable mental illness, 24 percent said they were moderately or severely disabled by it. But only 8 percent had ever sought professional help, and only 5 percent had ever seen a mental health professional.

People from rural areas were more likely to be depressed and have alcohol problems than urbanites, the study found. Mood and anxiety disorders were more common in people over 40 and among women, while alcohol abuse was much more common among men.

Although the authors did not reflect at length on the role of China’s economic rise, which has led to mass migrations of poor people to the cities, they acknowledged that they were measuring some effects.