It easy to understand why chronic pain and depression often go hand-in-hand, and now Japanese researchers, writing in the Journal of the American Geriatrics Society, have found that knee osteoarthritis patients are likelier to develop depression.

Of 573 osteoarthritis patients, aged 65 and older and without depression, 11.9 percent developed depressive symptoms after two years. “Examining elderly people’s responses to questions about pain at night and difficulties performing daily activities may be an efficient way of identifying those at high risk of developing depressive symptoms,” they write.

Recently, the connection between knee osteoarthritis and depression has been studied increasingly, but most of the studies have centered on radiographic changes not the ways that pain and knee function relate to symptoms of depression, the authors write. “Because depression has a strong negative effect on well-being, understanding its risk factors is important for public health,” they add.

Patients who had pain at night while in bed and who struggled to put on or to take off their socks or to get in or out of a car, were likelier to develop depression, reports MedPage.

In an interview with Everyday Health, Barbara Sommer, a psychiatry professor emerita at Stanford, spoke highly of the results and their application. “While the authors state that some phenomena seen in Japan (sleeping on futons, being very socially active in general) may not apply to all cultures, it is likely that their findings are generalizable,” she said in the interview.