What exactly is pain?
The International Association for the Study of Pain (IASP) defines it as “an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage”. That wording, revised in 2020, carries three essential ideas.
First, pain is always a personal experience: it does not show up on an X-ray and no blood test can measure it. Second, it has an emotional dimension that cannot be separated from the physical sensation; anxiety, fatigue and isolation genuinely amplify it, which does not make it imaginary. Finally, pain can exist without visible damage: the nervous system can generate a pain signal even when the tissues have healed or were never injured.
This last idea is the most widely misunderstood. Telling someone that “the tests are normal” never means their pain is not real: it means that the mechanism at work is not tissue damage, but a disturbance in the way pain information is processed.
The three main pain mechanisms
Identifying the mechanism is the decisive step: what works depends entirely on where the pain comes from.
Nociceptive pain
Tissue is damaged or threatened (a fracture, a burn, inflammation, osteoarthritis) and the nociceptors send a warning. The nervous system is working normally. This is the most familiar kind of pain, and it usually responds well to paracetamol and anti-inflammatories.
Find out moreNeuropathic pain
The nerve itself is damaged: diabetes, shingles, a slipped disc, chemotherapy, surgery. It shows up as burning, electric shocks, pins and needles or allodynia. Ordinary painkillers work poorly; certain anti-epileptics and antidepressants are used instead.
Find out moreNociplastic pain
Neither tissue damage nor nerve damage: the nervous system amplifies signals over the long term. This is the mechanism behind fibromyalgia, much chronic low back pain and irritable bowel syndrome. The answer rests mainly on graded exercise, pain education and cognitive behavioural therapy.
Find out more
Acute or chronic pain: a difference in kind
Pain is called acute pain when it is recent and limited in time. It has a purpose: it protects, it immobilises, it prompts you to seek help. It fades as the injury heals.
Beyond three months, or when it outlasts the expected healing time, it is called chronic pain. Since 2019 the International Classification of Diseases (ICD-11) has recognised it as a condition in its own right, not merely a symptom of something else. It affects around one adult in five in Europe and takes a toll on sleep, mood, work and social life.
Comparing the two situations
| Acute pain | Chronic pain | |
|---|---|---|
| Duration | Less than 3 months, often a few days | More than 3 months, or recurring |
| Function | A protective alarm signal | None; the pain has become the disease |
| Cause | Usually identifiable | Often multifactorial, sometimes with no lesion at all |
| Impact | Limited and temporary | Sleep, mood, work, social life |
| Aim of treatment | Remove the pain and treat the cause | Reduce the intensity, restore function and quality of life |
| Approach | Medication in most cases | Multimodal: movement, psychology, medicines, education |
What to do when pain starts to settle in
Four simple habits noticeably improve care, and above all the quality of the conversation with your doctor.
Describe it precisely
Note where it is, what it feels like (burning, a vice, an electric shock, a throb), when it happens, what eases it and what makes it worse. These words point directly to the underlying mechanism.
Put a number on it
Rate it from 0 to 10 several times a day for a week. A figure tracked over time is worth far more than a general impression.
Keep moving
Outside genuine emergencies, prolonged strict rest makes most musculoskeletal pain worse. Staying active within your limits is a treatment in its own right.
Seek help at the right time
Pain that lasts more than a few weeks, that wakes you at night, or that comes with fever, loss of strength or weight loss warrants prompt medical advice.
Frequently asked questions about pain
When is pain considered chronic?
Once it has persisted or recurred for more than three months, or when it lasts longer than the normal healing time for the tissues. This is the threshold used by the IASP and by the WHO's ICD-11 classification.
If the tests are normal, is the pain “all in my head”?
No. Normal tests rule out visible damage, not pain. Nociplastic pain results from a real, measurable amplification of signals inside the nervous system. The suffering is genuine, and a different kind of treatment exists for it.
Should I wait until the pain is bad before taking a painkiller?
No. A painkiller works better, and at a lower dose, when it is taken early, before the pain peaks. For predictable pain, doses are in fact prescribed at fixed times rather than on demand.
Does pain lessen with age?
Perception may change in older people, but pain remains just as real and just as common. Unfortunately it is under-assessed and under-treated in this group, particularly where there is cognitive impairment, in which case behavioural observation scales are used.
Can you become dependent on painkillers?
The risk mainly concerns opioids, especially with prolonged use and no review. It is managed through a clear indication, a limited duration, regular follow-up and a gradual reduction in dose once the treatment is no longer needed.
Where to go next
Choose the page that matches your situation.
Sources and references
- IASP — Terminology: revised definition of pain, 2020.
- World Health Organization — ICD-11, chapter MG30 “Chronic pain”, 2019.
- WHO — Guidelines for the pharmacological and radiotherapeutic management of cancer pain.
- Breivik H. et al., Survey of chronic pain in Europe, European Journal of Pain.