Inclusion Criteria:  Adults from 18 to 75 years-old. 1990 American College of Rheumatology (ACR) classification criteria + the 2011 modified ACR diagnostic criteria for fibromyalgia Able to understand Spanish and accept to participate in the study.  Exclusion Criteria:  Participating in concurrent or past RCTs (previous year). Comorbidity with severe mental disorders (i.e. psychosis) or neurodegenerative diseases (i.e. Alzheimer) that that would limit the ability of the patient to participate in the RCT.