"I expected there to be an increase [in antidepressant use], but I didn't expect the increase to be as large as we actually found," says Mark Olfson, MD, MPH, professor of clinical psychiatry at New York State Psychiatric Institute of Columbia University, who co-authored the study with Steven C. Marcus, PhD, of the University of Pennsylvania, Philadelphia.
''Ten percent of the population is being treated with an antidepressant during the course of a year," he says. That compares to 5.8% in 1996, he found.
Although part of the uptick can be linked to the fact that mental health treatment is becoming more common and accepted, Olfson tells WebMD that he fears the medications may sometimes be prescribed "in a casual way."
The study appears in the Archives of General Psychiatry.
Olfson and Marcus analyzed data from the Medical Expenditure Panel Surveys, sponsored by the Agency for Healthcare Research and Quality, which provides national estimates in the U.S. about health care use and costs.
For the 1996 survey, nearly 19,000 people aged 6 and older were included, and more than 28,000 in the 2005 survey. A designated adult in each household answered questions about prescribed medications, medical visits, and other information.
The rate of antidepressant treatment increased from 5.84% to 10.12 % -- or from 13 million people to about 27 million, the researchers found.
One exception to the trend involved African-Americans. "African-Americans really did stand out as one group that didn't experience a significant increase in antidepressant use," Olfson says. In 1996, 3.6% of African-Americans surveyed were on antidepressants and 4.5% in 2005.
Another important finding, Olfson says, is that fewer people on antidepressants surveyed in 2005 also took part in psychotherapy or "talk therapy." Although 31.5% of those surveyed in 1996 on antidepressants also did talk therapy, just 19.8% of those surveyed in 2005 both took antidepressants and participated in psychotherapy.
Often, the two are recommended together for depression.