**2. Materials and Methods**

#### *2.1. Participants*

The study was part of a larger project assessing cognition and emotional processing in FM [16,21,58]. In total, 52 patients diagnosed with FM and 32 healthy participants took part in the study. Given the higher prevalence of FM in women compared to men and with the aim of avoiding possible gender-related confounding, only women were included in the study. Patients were recruited through the Fibromyalgia Associations of Jaén and Úbeda (Spain). All of the patients met the American College of Rheumatology criteria for the diagnosis of FM [3]. Healthy participants were recruited through local advertisements. Exclusion criteria for all participants included metabolic abnormalities, neurological disorders (e.g., traumatic head injury), and severe somatic (e.g., cancer) or psychiatric (e.g., drug dependency, psychosis) diseases. The sociodemographic and clinical

data are shown in Table 1. Patients did not differ from healthy participants in terms age or years of education but showed a trend toward a higher BMI.


**Table 1.** Means (M) and standard deviations (SD) of the clinical and sociodemographic data of fibromyalgia (FM) patients and healthy controls. Results of group comparisons (t or χ2) are also displayed.

\* Note: Anxiety disorders include panic disorder, generalized anxiety disorder, phobias and adjustment disorder; n = number of participants. Non-opioid analgesic use includes the following analgesic drugs: non-steroidal antiinflammatory drugs, 29 patients; paracetamol, 34 patients; metamizole, 7 patients; anticonvulsants, 10 patients; tramadol, 20 patients; and codeine, 4 patients.

#### *2.2. Clinical Assessments*

The clinical history and sociodemographic data of the patients were obtained via a semi-structured interview. The Structured Clinical Interview for Axis I Disorders of the Diagnostic and Statistical Manual of Mental Disorders (SCID [59]) was used to check for psychiatric disorders, especially anxiety and depression. Clinical pain was quantified using the Spanish version of the McGill Pain Questionnaire (MPQ [60]). The following four scales from the MPQ were applied: sensory pain (score range: 0–84), affective pain (score range: 0–22), evaluative pain (score range: 0–4), and miscellaneous pain (score range: 0–30). The internal consistency (Cronbach's α) of the Spanish version of the MPQ ranges from 0.66 to 0.80 [61]. Depressive symptoms were assessed using the Spanish version of the Beck Depression Inventory (BDI [62]; score range: 0–63; Cronbach's α = 0.95). Levels of anxiety were assessed using the State-Trait Anxiety Inventory (STAI [63]; score range: 0–60 for both scales; Cronbach´s α = 0.93 for state anxiety and 0.87 for trait anxiety). Fatigue was assessed using the Spanish version of the Fatigue Severity Scale (FSS [64]; score range: 9–63; Cronbach´s α = 0.88). Insomnia was measured using the Oviedo Sleep Quality Questionnaire (COS [65]; score range: 9–45; Cronbach´s α = 0.77).
