Decline of substance P levels after stress management with cognitive behaviour therapy in women with the fibromyalgia syndrome.

Background and aims Substance P (CSF-SP) is known to be elevated in females with fibromyalgia syndrome (FMS). The aims of this study were to evaluate the effect of cognitive behaviour therapy (CBT) on plasma SP levels in women with FMS and to find possible clinical behavioural correlates to plasma SP level changes. Methods Forty-eight women with FMS were randomly allocated into two groups. Group 1 received the CBT treatment intervention over the course of 6 months while group 2 was waitlisted. CBT was given with a protocol developed to diminish stress and pain. After 6 months, group 2 was given the same CBT treatment as well. All were followed up 1 year after the start of CBT treatment. This approach allowed for two analytical designs - a randomised controlled trial (RCT) (n=24 vs. n=24) and a before-and-after treatment design (n=48). All women were repeatedly evaluated by the West Haven-Yale Multidimensional Pain Inventory (MPI) and three other psychometric questionnaires and plasma SP was analysed. Results In the RCT design, the plasma SP level was 8.79 fmol/mL in both groups at the start of the trial, after adjustment for initial differences. At the end of the RCT, the plasma SP level was 5.25 fmol/mL in the CBT intervention group compared to 8.39 fmol/mL in the control group (p=0.02). In the before-and-after design, the plasma SP was reduced by 33% (p<0.01) after CBT, but returned to the pre-treatment level at follow-up 1 year after the start of CBT treatment. Plasma SP was associated with the MPI dimensions experienced "support from spouses or significant others" and "life control". Conclusions Plasma SP might be a marker of the effect of CBT in FMS associated with better coping strategies and reduced stress rather than a biochemical marker of pain.