Would help to identify the neurobiological underpinnings of MBSR and increase our knowledge of FMS pathophysiology. The main objectives of this 12-month RCT are: firstly, to examine the effectiveness and cost-utility for FMS patients of MBSR as an add-on to treatment as usual (TAU) versus TAU + the psychoeducational programme FibroQoL, and versus TAU only; secondly, to examine pre-post differences