A study from the Centers for Disease Control and Prevention, or CDC, found that people with arthritis have high rates of depression and anxiety, that the conditions are underdiagnosed and that many of those affected don’t receive mental health treatment – which could potentially help with their physical symptoms.

The study, published online in the journal Arthritis Care & Research, was conducted by phone with almost 1,800 people, ages 45 and older, who had been doctor-diagnosed with a form of arthritis or related condition, such as lupus or fibromyalgia. Based on their responses to a questionnaire to determine emotional well-being, 31 percent of respondents were found to have anxiety and 18 percent had depression. There was significant overlap between the two conditions: 84 percent of those with depression also had anxiety, and 50 percent of those with anxiety also had depression.

However, only half of the people with these mental health issues sought treatment for them over the past year.

The correlation between depression and arthritis, especially rheumatoid arthritis, is well known, but this study suggests anxiety may be even more common than previously believed.

Louise Murphy, PhD, lead author of the study and director of the Arthritis Program in the Division of Population Health at the CDC, says she and colleagues were surprised to find that the rates of anxiety were so high.

“If we are focusing only on depression, we are missing a whole group of people with emotional distress,” she says.

Not everyone was surprised. Michael Clark, MD, director of the chronic pain treatment program in the department of psychology and behavioral sciences at Johns Hopkins University, says this new study only adds to what is already understood by experts in the field.

“We’ve known for a long time that psychological disorders of all types are increased in patients with chronic pain disorder,” Dr. Clark says. For instance, a World Health Organization study from the early 2000s found American adults with arthritis are more likely to have a range of anxiety disorders than people without arthritis. “The bugaboo on this is, despite a crushing amount of evidence that these exist in these patient populations, they are still underdiagnosed, poorly treated and misunderstood.”