The assessment of Quality of Life SF-36 covers 8 dimensions of health status. It contains 36 items covering two areas, the functional status and the emotional wellness. The area of the functional state is represented by the following dimensions: physical function (10 items), social function (2 items), role limitations due to physical problems (4 items), role limitations due to emotional problems (3 items). The wellness area includes the dimensions of mental health (5 items), vitality (4 items), pain (2 items). Finally, the general health assessment includes the dimension of perception of general health (5 items) and the health change over the time (one item, which is not part of the final score).

This simple clinical case definition of fibromyalgia properly classifies the 88.1% of the cases classified by the American College of Rheumatology classification criteria, and it does not require a physical or tender point. The Symptom Severity Score allows the assessment of the severity of the symptoms of fibromyalgia in people with current or previous fibromyalgia, and those in which the criteria have not been applied yet. This questionnaire is especially useful in the longitudinal assessment of patients with marked symptom variability.

The fibromyalgia impact questionnaire consists of 10 items. The first item is composed of 11 subitems in which is valued the physical function. In the second and third items, patients indicate the number of days in which they disrupt their daily activity due to pain, or otherwise the days they find improvement. The impact caused by the symptoms of fibromyalgia in the physical and mental health of the patients was measured by the Spanish version of the Impact of Fibromyalgia Questionnaire. This questionnaire assesses the following dimensions: feeling good, physical function, missing work and work capacity, physical, psychological and social components and global wellness. Also, it includes six visual analog scales for assessing fatigue, pain, stiffness, morning tiredness, anxiety and depression.

Pittsburgh Sleep Quality Index Questionnaire consists of 24 items, and which interrogate issues such as the quality of sleep that the subject he has, or the frequency of certain events - such as difficulty falling asleep during the first half an hour or the presence of nightmares- are answered by an ordinal scale with four grades. In the correction of this questionnaire, seven scores are obtained which inform us of the components of sleep quality: subjective quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, the use of hypnotic medication, and daytime dysfunction. Each of these components receives a discrete score which can range from 0 to 3. A score of 0 indicates that there are no problems in this respect, and a score of 3 indicates serious problems at that level. The sum of the scores in each partial component generates a total score, which can range from 0 to 21.

The Beck inventory for depression is a self-administered questionnaire of 21 items that assesses a wide range of depressive symptoms. Its content emphasizes more the cognitive component of depression, and the symptoms of this area represent about 50% of the total score of the questionnaire, with symptoms of somatic / vegetative. In the second block, of the 21 items, 15 refer to eco-cognitive symptoms, and the remaining 6 to somatic-vegetative symptoms. Each item has four response alternatives listed from low to high severity, assessing the severity / intensity of the symptom. The range of the score is 0-63 points. The aim of this questionnaire is to quantify the symptoms, not provide a diagnosis. The breakpoints usually accepted to graduate the intensity/severity are the followings:

• No Depression: 0-9 points.
• Mild depression: 10-18 points
• Moderate Depression: 19-29 points
• Severe depression: ≥ 30 points

The State-Trait Anxiety Inventory measures a stable personality dimension (trait anxiety or tendency to anxiety), also includes a subscale of state, to detect anxiety behaviors. In the questionnaire, consisting of 40 items (20 for each level), the subjects have to describe how they feel generally, in the case of the trait anxiety scale, and how they feel when they answer, in the case of anxiety scale as a state. This inventory allows obtaining the scores of both scales separately.