Depression puts psoriasis patients at significantly greater risk of psoriatic arthritis

Psoriasis is a long-lasting inflammatory skin disease characterized by red, itchy, and scaly patches of skin. Approximately 8.5% of psoriasis patients have psoriatic arthritis, which is characterized by psoriasis plus inflammation of and around the joints.

"For many years, the rheumatology and dermatology communities have been trying to understand which patients with psoriasis go on to develop psoriatic arthritis and how we might detect it earlier in the disease course," explained senior investigator Cheryl Barnabe, MD, MSc, of the McCaig Institute for Bone and Joint Health and the O'Brien Institute for Public Health, Cumming School of Medicine, at the University of Calgary, Alberta, Canada.

Depression is common among patients with psoriasis. Based on recent laboratory work demonstrating that major depressive disorder is associated with increased systemic inflammation, the team of researchers hypothesized that psoriasis patients who develop depression are at increased risk of subsequently developing psoriatic arthritis.

Investigators used The Health Improvement Network (THIN), a primary care medical records database in the United Kingdom, to identify over 70,000 patients with a new diagnosis of psoriasis. Through follow-up records, they identified individuals who subsequently developed depression and those who developed psoriatic arthritis. Patients were followed for up to 25 years or until they developed psoriatic arthritis.

Statistical analysis showed that patients with psoriasis who developed major depressive disorder were at 37% greater risk of subsequently developing psoriatic arthritis compared with patients who did not develop depression, even after accounting for numerous other factors such as age and use of alcohol.

The study highlights the need for physicians to manage patients with psoriasis to identify and address depression. This could include rapid, effective treatment of psoriasis and psychosocial management of the cosmetic burden of psoriasis. The study also draws into question the biological mechanisms by which depression increases the risk for developing psoriatic arthritis. These mechanisms may include altered systemic inflammation as a consequence of depression, or even the role of lifestyle behaviors such as physical activity or nutrition, which are typically worsened by depression, and which may place an individual at risk for psoriatic arthritis.

"There is a tendency to think of depression as a purely 'psychological' or 'emotional' issue, but it also has physical effects and changes in inflammatory and immune markers have been reported in depressed people," commented Scott Patten, MD, PhD, the O'Brien Institute for Public Health, Hotchkiss Brain Institute and Mathison Centre for Mental Health Research and Education, Cumming School of Medicine. "Depression may be a risk factor for a variety of chronic conditions and this research is an example of how big data approaches can identify these associations."

Laurie Parsons, MD, of the Cumming School of Medicine, added: "It is evident to physicians who treat patients with psoriasis, that there is a significant psychological and social burden associated with this disease, which is reflected in an increase in the rates of depression. This study brings us a little closer to understanding the role of chronic inflammation as a systemic player in both the physical and psychological manifestations of psoriasis and underscores the need for closer attention to symptoms of depression in this group of patients."

"This study raises important questions on the role of systemic inflammation, which is also elevated in depression, in driving a disease phenotype, which needs to be confirmed in clinical cohorts," concluded Dr Barnabe.