The International Association for the Study of Pain (IASP) defines pain as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage". Put it simply, it is the experience generated by our nervous system when it interprets that there is, or may be, a threat to our body.
This definition has marked a significant paradigm shift because it separates concepts that we long considered virtually equivalent: pain and harm are not the same thing.
Despite being a universal experience, every human being experiences pain in a different way. This is because its perception is influenced by hormonal, immune, psychosocial, occupational and family factors, the condition of our tissues and physical fitness, the functioning of the nervous system, our expectations and previous experiences, and even what we know about pain and the way in which we receive and/or understand a diagnosis.
When faced with an injury or a potential threat, the nervous system integrates the information from the tissues along with that provided by all these factors and assesses, unconsciously, the significance of the situation. Pain is the result of this process, not a simple reflection of existing damage. That is why, in response to the same physical stimulus, two people may experience very different types of pain, or even the same person may experience different symptoms depending on the time and context.
For a long time, medicine interpreted pain from a much more simplistic perspective: if pain occurred, there must be an injury to explain it. When no such injury was identified in routine tests, the pain was frequently attributed to exclusively psychological factors. Although our understanding has advanced enormously, this view still persists in some areas of clinical practice. Many patients, particularly women, continue to have their experience questioned or downplayed, interpreted as a manifestation of anxiety, stress or emotional distress.
If there is no injury to explain my pain, why does it hurt?
The fact that an imaging scan does not show an injury does not mean that there is no biological abnormality. In some types of persistent pain, the problem lies in the very functioning of the nociceptive system – the network responsible for detecting and processing signals of potential danger.
Thanks to techniques currently used in research, we know that this system can alter its functioning and become overly reactive. This is what we know as sensitization: the alarm mechanisms are triggered more easily; they amplify the signals and may even remain active when the initial threat has already disappeared. In this situation, the pain generated shifts from being secondary to being termed “primary”, as the injury, if any, no longer fully explains the painful experience.
So, how is primary pain diagnosed?
There is no single test that can diagnose it. The process begins with something much more basic, yet essential: a thorough medical history and physical examination. We must understand how the pain began, its progression, characteristics and mechanisms…as diagnosing it does not mean “finding nothing”, but rather recognizing its specific characteristics – whilst, of course, first ruling out the possibility that a disease accounts for some or all of the symptoms.
This new approach has led Hospital Clínic Barcelona to evolve from a model focused primarily on fibromyalgia (the best-known example of primary pain) to become the first hospital-based Primary Chronic Pain Unit in Spain, broadening our focus and delving particularly deeply into the diagnostic process before starting treatment. The aim is to avoid under-diagnosis or labelling something as fibromyalgia or primary pain when it is not, which may influence the patient’s future care and prognosis. Because a diagnosis should never prevent us from continuing to seek answers when something does not add up.
