The Effect of Anxiety and Depression on Improvements in Pain in a Randomized, Controlled Trial of Pregabalin for Treatment of Fibromyalgia

ABSTRACT

Objective. To assess symptoms of anxiety and depression in a large cohort of fibromyalgia patients and to determine the impact of these symptoms on response of pain to pregabalin treatment.

Design. Patients completed the Hospital Anxiety and Depression Scale at the baseline visit in a randomized, controlled trial of pregabalin for treatment of fibromyalgia. Mean anxiety and depression subscale scores were calculated, and proportions of patients by symptom severity were determined. The difference between the proportion of patients reporting anxiety and depression at baseline was tested using McNemar's test. Baseline anxiety and depression were evaluated as covariates by including them—as interaction terms with treatment—in an ancova model. A path analysis evaluated the association between improvements in anxiety and depression and pain relief.

Results. In total, 529 patients were enrolled. Significantly more patients reported anxiety symptoms (71%) than depressive symptoms (56%) (P < 0.0001). Improvement in pain symptoms with pregabalin compared with placebo did not depend linearly on baseline anxiety or depression scores. By path analysis, 75% of the pain reduction was not explained by improvements in anxiety and depressive symptoms.

Conclusions. Anxiety symptoms were more common than depressive symptoms in this cohort. Our results suggest patients with fibromyalgia should be routinely assessed for the presence of both anxiety and depression. The pain treatment effect of pregabalin did not depend on baseline anxiety or depressive symptoms, suggesting pregabalin improves pain in patients with or without these symptoms. Much of the pain reduction appears to be independent of improvements in anxiety or mood symptoms.