To explore the possibility that cognitive-behavioral therapy (CBT) influences fibromyalgia symptoms via descending inhibition of nociception, we evaluated the effects of CBT on the nociceptive flexion reflex (NFR) threshold, an objective measure of spinal nociceptive transmission.
Female fibromyalgia patients (n = 32) were randomized to 6 weekly sessions of telephone-delivered CBT or usual care (UC). Assessments of the NFR threshold and clinical outcomes were conducted at baseline, week 6 (post-CBT), and week 12.
From baseline to week 6, the NFR threshold increased in the CBT group and decreased in the UC group (mean +/- SD 4.4 +/- 13.7 mA versus -10.2 +/- 9.9 mA; P = 0.005). This difference was also apparent at week 12 (mean +/- SD 7.3 +/- 9.2 mA for CBT versus -5.4 +/- 13.5 mA for UC; P = 0.01). The groups reported similar reductions in NFR pain ratings at week 6 (mean +/- SD -20.2 +/- 23.9 for CBT versus -14.9 +/- 16.4 for UC; P = 0.8) and week 12 (mean +/- SD -8.9 +/- 25.3 for CBT versus -10.8 +/- 24.1 for UC; P = 0.4).
Compared with UC, CBT reduced nociceptive responding in fibromyalgia patients. Moreover, while the UC group exhibited longitudinal decreases in both the stimulation level and pain associated with the NFR threshold, those receiving CBT required more intense stimulation to elicit the NFR as well as rated that stimulation as less painful than at baseline. These data indicate the need for a larger study to confirm that changes in nociceptive responsivity may underlie the benefits of CBT in fibromyalgia patients.