We read with great interest the recently published article in Arthritis Care & Research by Fuller-Thomson and Shaked on factors associated with depression and suicidal ideation among individuals with arthritis (1). Mental health is an important component of health among patients with chronic diseases such as arthritis (2), and we agree with the authors that knowledge of risk factors for depression and improved screening and outreach for psychotherapeutic interventions can help improve the overall health of people with arthritis. The prevalence of serious psychological distress, frequent anxiety, and depression has been reported to be higher in adults with arthritis than in those without arthritis (3). In the study by Fuller-Thompson and Shaked, 9.9% of persons with arthritis experienced a major depressive episode in the preceding 12 months, compared with 6.8% of persons without arthritis. However, items included in the mental health interview scale used in the study may have overestimated the difference in the prevalence of major depression between those with and without arthritis.
Large population-based and community surveys often employ abbreviated diagnostic interviews administered by lay interviewers. The Composite International Diagnostic Interview Short-Form (CIDI-SF), which screens for a major depressive episode (4), was used in the Canadian Community Health Survey (CCHS) (1). The Behavioral Risk Factor Surveillance System of the US Centers for Disease Control and Prevention uses the Kessler 6/10 (K6), which screens for nonspecific psychological distress (5). Each of these measures is based on the Diagnostic and Statistical Manual criteria. However, the mental health items of these measures may be influenced by physical health and may not operate as a “pure” measure of mental health. For example, the CIDI-SF, a measure of a major depressive episode in the preceding 12 months, inquires of the patient, “Did you feel tired out or low on energy all the time?” and “Did you have more trouble falling asleep than you usually do?” Similarly, the K6 has 6 questions that assess how often during the past 30 days a respondent felt “so sad that nothing could cheer them up,” “nervous,” “restless,” “hopeless,” “worthless,” or that “everything was an effort.” It is possible that individuals with arthritis may misinterpret the questions in the CIDI-SF (“Did you feel tired out or low on energy all the time?”) or in the K6 (“How often in the past 30 days did you feel that everything was an effort?”) as part of their physical symptoms rather than as part of their mental health. Similar misattribution of physical symptoms to mental health has been noted in clinical studies of the Center for Epidemiologic Studies Depression Scale (CES-D) in patients with rheumatoid arthritis (6). Researchers should consider the possibility of misattribution when such scales are administered, as well as whether the items in the scale may lead to an overestimate of the true burden of mental health disorders in persons with arthritis or other chronic physical conditions. Additional research into the validity of the scale items as they pertain to individuals with arthritis is needed.