Relationships among pain and depressive and anxiety symptoms in clinical trials of pregabalin in fibromyalgia.

Background: Fibromyalgia, as defined by the American College of Rheumatology, is characterized by widespread pain lasting for at least 3 months, with pain in at least 11 out of 18 tender points when palpated with digital pressure.

Objective: The authors investigated the relationship between changes in pain and symptoms of anxiety and depression, using data from pregabalin clinical trials.

Method: Results from three double-blind, placebo-controlled trials of pregabalin monotherapy in fibromyalgia (8-14 weeks) were pooled, and baseline to end-point changes in pain and Hospital Anxiety and Depression Scale (HADS) scores were analyzed. Path-analysis evaluated the association between improvements in anxiety and depression and pain relief.

Results: Baseline HADS scores indicated moderate-to-severe anxiety in 38% of patients and moderate-to-severe depressive symptoms in 27%. The improvement in pain was not related to baseline levels of anxiety or depression. The correlation between changes in pain and depressive or anxiety symptoms was low-to-moderate. Path-analysis showed that most of the pain relief observed with pregabalin treatment was a direct analgesic effect and was not explained by improvement in mood.

Conclusion: Response to treatment of pain in the pregabalin trials did not depend on baseline levels of anxiety or depressive symptoms, and pregabalin improved pain in fibromyalgia patients with or without depressive or anxiety symptoms. Changes in the level of anxiety or depression had a low-to-moderate impact on pain reduction. Pain reduction with pregabalin treatment appeared to result mostly from a direct treatment effect, rather than an indirect effect mediated through improvement in anxiety or depressive symptoms.