For people with a painful cartilage condition, common pain relievers may have small benefits for depression symptoms as well, a new study hints.

Depression is more than twice as common among people with osteoarthritis, which happens when cartilage wears down around the hands, lower back, knees or other joints.

As many as 27 million Americans have osteoarthritis, according to the Centers for Disease Control and Prevention. To help manage their pain, those patients often take nonsteroidal anti-inflammatory drugs, or NSAIDs, like ibuprofen or naproxen.

"This work suggests that anti-inflammatory agents may play a role in reducing the burden of depression," senior author Dr. Michael E. Farkouh of Mount Sinai School of Medicine in New York, said.

His team's study includes data from five previous trials of over-the-counter NSAIDs and prescription Celebrex, a NSAID manufactured by Pfizer, which provided the Celebrex results. In each of the trials, people with osteoarthritis were randomly assigned to take one of those medications or a drug-free placebo pill for six weeks.

Almost 1,500 people not taking antidepressants took part in the studies, which involved multiple depression questionnaires.

People on each treatment, including the placebo, tended to report fewer depression symptoms at the end of the trials than at the beginning, according to results published in The American Journal of Medicine.

But depression scores - measured on a scale of 0 to 27 - fell by 0.3 more points in the over-the-counter NSAID groups and by 0.6 more points in the Celebrex groups than among people taking a placebo.

Arthritis patients started those studies with an average depression score of 3, far below the threshold of 10 used for a depression diagnosis.

"The relationship between depressive symptoms and chronic pain is complex, and important," David A. Walsh, director of the Arthritis Research UK Pain Centre in Nottingham, said.

Survey responses which are used to diagnose depression can sometimes be explained by physical pain, which makes results difficult to interpret, he said.

Trouble falling or staying asleep or trouble concentrating, for example, can be symptoms of either depression or distracting pain.

Though the researchers tried to take that into account, it's difficult to completely untangle the effects of pain on mood, Walsh told Reuters Health in an email. So the apparent influence of NSAIDs on depression may have just been due to a lessening of osteoarthritis pain, he said.

The study does provide some evidence that at least one form of pain medication may help reduce depression among people with osteoarthritis, Walsh said. It also "raises an interesting mechanistic question as to whether NSAIDs may have direct effects on mood, independent of their analgesic activity."

But based on these results, depressed people with osteoarthritis shouldn't be selectively given NSAIDs in hopes of easing their depression just yet, he said.

Doctors should follow existing guidelines when recommending or prescribing NSAIDs for arthritis pain, researchers said.

Farkouh said future studies should look at the connection between NSAIDs and depression, as that could help researchers learn whether inflammation plays a role in the disease.

Although the average changes in depression symptoms seen in his study would not be enough for patients to notice in their everyday lives, they may be for some people, Farkouh said. "That's why we need more work to figure this out."