Antidepressants became the third most commonly prescribed class of medications in the United States thanks in part to non-psychiatrist providers prescribing the drugs to individuals without any psychiatric diagnosis, according to a new study led by researchers at the Johns Hopkins Bloomberg School of Public Health.

"We’ve seen a marked increase in antidepressant use among individuals with no psychiatric diagnosis. Nearly four out of every five antidepressant prescriptions are written by non-psychiatrist providers," said Ramin Mojtabai, MD, PhD, MPH. He was lead author of the study and an associate professor with the Bloomberg School’s Department of Mental Health.

"Between 1996 and 2007, the number of visits where individuals were prescribed antidepressants with no psychiatric diagnoses increased from 59.5 percent to 72.7 percent and the share of providers who prescribed antidepressants without a concurrent psychiatric diagnosis increased from 30 percent of all non-psychiatrist physicians in 1996 to 55.4 percent in 2007."

The results are featured in the August 2011 issue of Health Affairs.

"To the extent that antidepressants are being prescribed for uses not supported by clinical evidence, there may be a need to improve providers’ prescribing practices, revamp drug formularies or undertake broad reforms of the health care system that will increase communication between primary care providers and mental health specialists," Mojtabai added.

From 2005 to 2008, nearly 9 percent of the U.S. population had at least one prescription for an antidepressant medication any given month, according to the Centers for Disease Control and Prevention.

Pharmaceutical companies have encouraged physicians to prescribe medications for off-label use.

A study published in January in the American Journal of Public Health found drugs that pharmaceutical companies marketed most aggressively to physicians and patients tended to offer less benefits and more harm to patients.

"This is not a random occurrence, but rather a repeating, planned scenario in which drugs, discovered with good science for a specific set of patients, are marketed to a larger population as necessary, beneficial and safer than other alternatives," Howard Brody, a professor and director of the Institute for the Medical Humanities at UTMB Health and co-author of the study, said.

"Marketers are just doing their jobs. However, the reality is that for most new drugs, safety and efficacy are scientifically proven for only a small subset of patients. It’s time for physicians to take a stand and not prescribe them so readily."