Various studies have demonstrated a link between having arthritis, particularly rheumatoid arthritis (RA) and osteoarthritis (OA), and psychiatric disorders. More than two decades ago, Wells et al.  published data from the NIMH catchment area study in the United States showing that persons with arthritis had a lifetime prevalence rate of psychiatric disorders of 63.6 percent and a 6-month prevalence rate of 42.8 percent. These rates were alarming in as much as they exceeded those found in persons with potentially life-threatening illnesses such as COPD, diabetes, hypertension, and cardiovascular disease. While the authors found that having any chronic illness increased the risk of psychiatric disorder, these cross-sectional, epidemiological data did not address the important questions of whether arthritis preceded or followed the development of psychiatric disorders, or why these associations were found in the first place. Subsequently, corroborating evidence has been found in studies reporting rates of mood disturbance ranging from 15 percent to as high as 45 percent in persons with such conditions as rheumatoid arthritis, systemic lupus erythematosus, and fibromyalgia [1,5,13]. Evidence also is accumulating that anxiety disorders are prevalent in persons with arthritis . Understanding the factors associated with the heightened psychiatric co-morbidity in such studies represents an important challenge for behavioral medicine researchers and arthritis health professionals who serve these populations.
Accordingly, the major purpose of the Land et al.  study was to clarify the direction of the relationship between arthritis and psychiatric disorders by examining whether arthritis increased the risk for developing psychiatric disorders, or whether having psychiatric disorders increased the risk for developing arthritis. Using an epidemiological approach in which participants were interviewed in their homes and followed longitudinally across 90 municipalities in the Netherlands, the researchers found that persons with arthritis had significantly higher concurrent risk for mood and anxiety disorders than those without arthritis and conclusive evidence that arthritis contributed to the development of mood disorders over time. Conversely, having a psychiatric disorder did not increase the risk of developing arthritis. Methodological advantages of this research, including a sophisticated, population-based sampling approach, a two-year follow up, and the adoption of an objective measure of psychiatric disorders designed for epidemiological research, add weight to these findings and represent a significant improvement over previous studies in this area.