MONDAY, Jan. 22 (HealthDay News) -- Men and women in their 50s and older who take antidepressants known as selective serotonin reuptake inhibitors may be doubling their risk of fractures, a new Canadian study suggests.

SSRIs, such as Prozac and Paxil, are commonly used to treat depression and anxiety. But previous studies had shown these drugs are associated with an increased risk of fractures from falling.

The new research, led by Dr. David Goltzman, a professor of medicine and physiology and director of the McGill Centre for Bone and Periodontal Research at McGill University in Montreal, seems to support the earlier studies.

"There is good scientific evidence that serotonin is involved in bone physiology, and if you alter the system, you can get low bone density," Goltzman said. "Patients should be monitored to prevent the risk of fractures."

The finding is published in the Jan. 22 issue of the Archives of Internal Medicine.

For the study, Goltzman and his colleagues reviewed information on 137 patients -- average age 65 -- who took SSRIs. The patients had their bone mineral density measured at the start of the study and were followed for five years. Each year, the patients were also asked to report any fractures they had and how they occurred.

Goltzman's team found these patients had twice the risk of fractures. They were particularly vulnerable to breaks of the forearm, ankle and foot, and less so to fractures of the hip, rib, femur, and back, the study found.

Goltzman's group also found that use of SSRIs was associated with an increased risk of falling. The effect depended on the dose of the drug. Doubling the dose resulted in a 1.5-fold increase in the risk of falling.

Daily SSRI use was also associated with a 4 percent decrease in bone mineral density at the hip, and a 2.4 percent decrease at the spine, the researchers reported.

Patients need to know there's this risk of fractures with SSRIs, Goltzman said.

"Patients should not be told not to take SSRIs if they need them for depression," he said. "But this is a new risk that has been identified, and patients should take general steps to prevent osteoporosis. And they should have a bone density measurement before starting SSRIs and periodically after that."

But one expert said he thought the study failed to prove that SSRI use is linked to an increased risk of bone breaks.

"These findings are hard to interpret," said Dr. Robert P. Heaney, a professor of medicine at the Osteoporosis Research Center at Creighton University in Omaha, Neb. "Increased fracture risk has been associated with depression for years," he added.

Heaney said that to really uncover the role SSRIs may play in fractures, a study would have to compare depressed patients taking SSRIs with depressed patients taking other medications. "Then you could see if it was the depression causing the fractures or if it were the SSRIs. It may not be the SSRI at all," he said.

Studies like Goltzman's run the risk that people will stop taking their medication, Heaney said. "These kind of studies do some potential harm," he said.

More information

The U.S. National Institute of Mental Health can tell you more about depression.