A Canadian study suggests that people over 50 on a certain type of antidepressant are twice as likely to suffer bone fractures.

The study is published in the Archives of Internal Medicine.

The research was conducted by a team of scientists from various Canadian research centres.

They looked at data from a group of patients of average age 65.1 who were aged 50 and over who were taking SSRI antidepressants on a daily basis. These patients were part of a larger study under the umbrella of the Canadian Multicentre Osteoporosis Study (CaMos) Research Group. The CaMos group comprises a randomly selected, population-based cohort of 5008 adults aged 50 and over who are followed over 5 years for incident fractures.

The patients had been filling in questionnaires about their bone breakages cause by various minor events such as falling out of bed, off a chair, or similar minimal trauma incidents. All the fractures had been confirmed with radiographs.

The researchers found 137 patients within the CaMos cohort who were using SSRIs on a daily basis. The SSRIs they were using included: fluvoxamine (brand name uvox), citalopram (Celexa), fluoxetine (Prozac), sertraline (Zoloft) and paroxetine (Paxil). These were the ones that were on the market at the start of the CaMos study.

After correlating the data from the bone fractures with the data on the SSRI intake, the results showed that taking SSRI antidepressants every day doubled the risk of "clinical fragility fracture" in adults aged 50 and over, even after taking into account various other factors such as age, hip bone mineral density, and estrogen levels.

The also found a dosage effect, where a 1.5 increase in risk of bone fracture was linked to a doubling of daily dose of SSRI.

Since fragility fractures are already common in the over 50s, this additional risk could have significant health consequences for them.

The motive for the study came from knowing that fragility fractures and depression are not uncommon in the over 50s, and SSRIs are a commonly prescribed medication for depression in this age group. But the researchers were not aware of any studies that had tried to link the two together.

The researchers suggest that doctors should take into account the risk of fragility fracture when they prescribe SSRI antidepressants to patients in this age group.

Selective serotonin reuptake inhibitors (SSRIs) are antidepressants used to treat anxiety and personality disorders and depression. They increase the level of serotonin in the brain by stopping it being reabsorbed by the presynpatic cell, which leaves more of it around to produce its mood-altering effects.

"Effect of Selective Serotonin Reuptake Inhibitors on the Risk of Fracture."
J. Brent Richards, Alexandra Papaioannou, Jonathan D. Adachi, Lawrence Joseph, Heather E. Whitson, Jerilynn C. Prior, David Goltzman.
Arch Intern Med. 2007;167:188-194.