Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage (International Association for the Study of Pain).

El dolor es considerado un síntoma. Su mecanismo se considera vital, ya que es una defensa que tiene el cuerpo para detectar y localizar algún proceso que este causando daño. El dolor esta asociado a la percepción de cada sujeto, por lo que la intensidad puede o no estar vinculada con la gravedad del fenómeno que lo esta produciendo.

Pain is considered a sympton. Its mechanism is considered vital, since it is a defense that the body has to detect and locate some process that is causing damage. Pain is associated with the perception of each subject, so the intensity may or may not be linked to the severity of the phenomenom that is producing it. Pain is no longer considered a sympton and is taken into account as a disease when it becomes chronic, affecting the quality of life of the patient who suffers from it, producing alterations in daily activities, insomnia, mood changes, anxiety and depression.

It is estimated that chronic pain affects 25-29% of the world´s population. Aproximately 30 million people in Mexico have chronic pain, with a reported prevalence in men over 60 years of 41.5%, and in women over 60 years is 48%. In 2014, the prevalence of chronic pain in Mexico varied from 16-70%, being more frequent in women than in men, and was associated with degenerative disease and in those over 65 years of age.

According to its duration, pain can be classified as acute of chronic. Acute pain has a short and limited duration, is generally associated with an injury or disease, and disappears with the healing of the latter. Chronic pain lasts beyond the healing of the injury or disease that caused it or is associated with a chronic condition. Sometimes it is not posible to clearly identify the cause of chronic pain.