Effect of light and season on pain and depression in subjects with rheumatic disorders.

The clinical and neurochemical association between depression and season noted in seasonal affective disorder (SAD) has suggested that clinical pain might also be linked to season, perhaps through similar neurochemistry or the known association of depression with pain. We investigated the pain-light season/dark season hypothesis in 2523 rheumatic disease outpatients by examining VAS Pain and VAS Global Severity scores, as well as levels of depression and functional disability. No clinically significant difference in pain severity between season (or individual month) was noted for the consecutive outpatients at their first clinic visit, nor in sub-analyses using paired light and dark season visits. A slight trend toward increased pain severity in lighter months by about 3% compared to darker months was identified. No effect of season was seen on depression scores. In a subset of patients with high depression scores, rheumatoid arthritis and osteoarthritis patients, respectively, reported 16% and 7% greater pain scores in light compared to dark months, but fibromyalgia patients had stable scores. Season does not appear to play an important role in pain and/or depression in rheumatic disorders.