Bidirectional Association Between Depression and Fibromyalgia Syndrome: A Nationwide Longitudinal Study.

Several cross-sectional studies have reported a common comorbidity between depression and fibromyalgia syndrome (FMS). However, a bidirectional temporal association between these 2 distinct diseases has rarely been investigated. Using the Taiwan National Health Insurance Research Database, 25,969 patients with FMS and without any psychiatric disorder and 17,142 patients with depression and without FMS between 2000 and 2008 were enrolled and separately compared with age- and sex-matched (1:4) control groups. Patients with FMS who developed a new-onset depression and those with depression who developed new-onset FMS were identified during follow-up (to the end of 2011). The conditional Cox regression analyses, after adjustment for demographic data and medical comorbidities, showed that the patients with FMS were associated with an increased risk (hazard ratio [HR] 7.46, 95% confidence interval [CI] 6.77-8.22) of subsequent depression and that those with depression were associated with an increased risk (HR 6.28, 95% CI 5.67-6.96) of subsequent FMS. Our results supported a bidirectional temporal association between depression and FMS. Each disease occurring first may increase the risk of the other subsequently. Further study may be necessary to determine the underlying mechanism between depression and FMS and to clarify whether a prompt intervention for depression or FMS may decrease the risk of the other later in life. Perspective: Our study supported a bidirectional temporal association between depression and FMS such that each disease occurring first may increase the risk of the other subsequently. This result may imply a shared pathophysiology between FMS and depression, but further investigation is needed.