Mental illnesses including anxiety disorders and depression are common and under-treated in many developed and developing countries, with the highest rate found in the United States, according to a study of 14 countries.

Based on face-to-face diagnostic surveys in the homes of 60,463 adults, the study found that mental ailments affect more than 10 percent of people queried in more than half the countries surveyed.

Rates ranged from 26.4 percent of people in the United States to 8.2 percent of people in Italy. While Nigerians appeared to have the lowest prevalence of mental illness — 4.7 percent — the researchers think the actual number is likely much higher since residents of the violence-prone West African nation may be hesitant to confide in strangers.

“In some countries there just is not this tradition of public opinion and speaking your mind,” said Ronald Kessler, a Harvard Medical School researcher who led the study.

Anxiety widespread

Interviewers who were not psychiatrists spent about two hours asking questions, using a mental health survey that has been shown to be an effective diagnostic tool. Psychiatrists are re-interviewing some participants in every country to verify the results, Kessler said.

The study was done in 2001-2003 in Belgium, China, Colombia, France, Germany, Italy, Japan, Lebanon, Mexico, the Netherlands, Nigeria, Spain, Ukraine and the United States. Results appear in Wednesday’s Journal of the American Medical Association.

The most common ailments everywhere except Ukraine were anxiety disorders, which include panic attacks, phobias and post-traumatic stress disorder. In Ukraine, where unemployment is rampant as the country struggles with westernization, mood disorders including depression topped the list, Kessler said.

Questions on some disorders, including bulimia and attention deficit disorders, were not asked in every country, at least partly because they were thought to be relatively uncommon. The researchers said that limitation and relying on people to be truthful about their health may have led to underestimates.

“In every country there is a hidden or unhidden stigma,” said co-researcher Dr. T. Bedirhan Ustun of the World Health Organization. “People are reluctant to admit that they have mental problems.”

This may be slightly less true in the United States, where mental illness has been highly publicized in recent years, so the U.S. rate may not be that much higher than in other countries surveyed, Ustun said.

Kessler said it’s plausible that the U.S. rate would be higher because of “higher expectations” of success that can lead to frustration when people can’t live up to them.

According to the researchers, “Substantial proportions of serious cases receive no treatment” in every country studied.

'Misallocation of treatment resources'

In developed countries, about 36 percent to 50 percent of people with serious symptoms were untreated in the previous year. In developing nations, between 76 percent and 85 percent of serious cases were untreated.

In all countries, a substantial proportion of people with less severe cases received treatment, suggesting a “misallocation of treatment resources,” the researchers said.

Kessler said reasons for under-treatment include lack of access to health care in many regions. Also, Ustun said, in many countries insurance doesn’t adequately cover mental health treatment and doctors who fail to detect it are not considered as neglectful as those who fail to diagnose physical ailments such as high blood pressure.

“Better health care systems and training” are needed to address the problem, Ustun said.