En español | More doctors who are not psychiatrists are offering antidepressants to patients, often for vague complaints of fatigue, headaches or gloominess.

See also: Do antidepressants work?

Antidepressants are the third most commonly prescribed type of drug in the U.S. — Photo by Joseph Rodriguez/Gallery Stock

Indeed, the practice of prescribing these drugs without a diagnosis of depression is escalating and more common in men and women over age 50.

Nearly four of every five prescriptions are written by primary care doctors and specialists untrained in psychiatry who are dispensing powerful drugs that may have either no impact or harmful effects.

Antidepressants are now the third most commonly prescribed class of drugs in the United States, according to a study in the August issue of Health Affairs. (Prescription painkillers and cholesterol-lowering drugs were the first and second most prescribed drugs, the study reports.) Antidepressants also are one of the most costly medications to the health care system, with annual sales of approximately $11 billion.

The drugs are effective for a limited number of conditions, including clinical depression, chronic depression and some anxiety disorders.

"My sense is that we now have a large group of people taking them for unclear reasons," says coauthor Mark Olfson, M.D., a professor of clinical psychiatry at Columbia University. "And when you treat less severe problems, it becomes harder to demonstrate that they're helpful at all."

The study looked at information from surveys conducted by the Centers for Disease Control and Prevention that considered more than 230,000 visits by adults to offices of primary care doctors and specialists who were not psychiatrists.

Researchers found that 73 percent of prescriptions for antidepressants were written for patients with no formal diagnosis of depression in 2007, compared with 60 percent in 1996.

The share of doctors who prescribed antidepressants without such a diagnosis increased from 30 percent to 55 percent in the same period. The typical patient who received antidepressants without a formal diagnosis was a white woman over 50 who had high blood pressure, diabetes or several medical problems.

Next: What depression is, and isn't. >>