Participants are exposed to several words of emotional contents (positive, and negative). The differences between these words will allow the regulation and counter regulation of emotional processes (Schwager y Rothermund, 2013). The words are related to clinical and personal characteristics of the patients and they will promote an emotional identification that improve the emotional regulation (Kashdan, Barret y McKnight, 2015).

Participants are exposed to several neutral words. These words do not have any emotional content and there are no reasons to think that they have any effect over the emotional regulation.

Participants do not receive the intervention.

PbRE is a word reading task implementing through an App developed for smartphones. The patient will choose emotional positive and negative words related to personal and clinical characteristics.

The Combined Index of Severity in Fibromyalgia (ICAF) is a questionnaire that allows the classification of patients by severity in clinical practice. This analysis is a self-report questionnaire of 59 items constructed with the most common clinical manifestations of FM (Vallejo, Rivera, & Esteve-Vives, 2010). The ICAF questionnaire offers total scores, where higher scores indicate a more severe disease. This questionnaire also provides four factors: emotional, physical (pain, fatigue, sleep quality and functional capacity), active coping, and passive coping. Similar to the total score, higher scores on each factor indicate greater severity, with the exception of the active coping factor, where higher scores indicate a better way to cope with the disease.

The Fibromyalgia Impact Questionnaire (FIQ) (Burckhardt, Clark, & Bennett, 1991; Rivera & González, 2004) is a self-report questionnaire designed to evaluate the impact of the FM on the life of the patient. This 10-item questionnaire is widely used and covers the principal areas of interest, including physical functioning, pain, sleep, mental health, and fatigue. The score ranges from 0 to 100, where higher scores indicate a more severe impact of the disease.

The EuroQol-5D-L questionnaire (Herdman et al., 2011) is divided into 2 sections. The first section contains 5 questions about mobility, self-care, usual activities, pain/discomfort and anxiety/depression. Five levels for answering are included (no problems, slight problems, moderate problems, severe problems and extreme problems), ranging from 1 to 5. The second part is a VAS score, which records the responder's self-evaluated health, where 0 is worst imaginable health and 100 is best imaginable health.