What Is Pain? Acute and Chronic Pain, Causes and Treatment

Created: 16.01.2023 · Last Updated: 19.08.2026 · Category: Health and Technology · Prepared by the Academic Hospital Web and Editorial Board.

What Is Pain?

Pain is not simply a direct measurement of tissue damage. The International Association for the Study of Pain describes pain as an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.

Pain is a personal experience influenced to varying degrees by biological, psychological and social factors.

For this reason, two people with similar medical conditions or imaging findings can experience very different levels of pain and disability.

Severe tissue damage does not have to be visible on imaging for pain to be real. Pain can be influenced by the nervous system, tissue condition, sleep, stress, previous experiences and other factors.

What Is the Difference Between Acute and Chronic Pain?

Acute Pain

Acute pain is newly developed pain that is often related to injury, surgery, infection or another medical condition.

It can serve an important protective function by warning the body of danger. Acute pain usually decreases as the underlying condition heals or resolves.

Chronic Pain

Chronic pain is pain that persists or recurs for more than three months.

In some cases an ongoing disease or tissue problem is present. In others, pain can continue even after the original injury has healed because pain-processing mechanisms in the nervous system have changed.

What Are the Different Pain Mechanisms?

Nociceptive Pain

Nociceptive pain results from actual or threatened damage to non-neural tissue and activation of pain receptors. Examples can include fractures, muscle injuries, osteoarthritis and postoperative pain.

Neuropathic Pain

Neuropathic pain is caused by a lesion or disease affecting the somatosensory nervous system.

Diabetic neuropathy, post-herpetic neuralgia and some nerve injuries are examples. It can be experienced as burning, electric shocks, tingling or numbness.

Nociplastic Pain

Nociplastic pain is associated with altered pain processing and cannot be fully explained by clear tissue damage or a lesion of the somatosensory nervous system.

Nociplastic mechanisms can contribute to conditions such as fibromyalgia.

More than one pain mechanism can be present in the same person.

What Can Cause Pain?

  • Musculoskeletal conditions: back and neck disorders, osteoarthritis, rheumatoid arthritis and soft-tissue injuries
  • Head and facial pain: migraine, tension-type headache, trigeminal neuralgia and secondary headache disorders
  • Nervous-system conditions: diabetic neuropathy, post-herpetic neuralgia and nerve injuries
  • Visceral conditions: kidney stones, gallbladder disease and gastrointestinal disorders
  • Surgery or trauma: acute postoperative pain or persistent postsurgical pain
  • Cancer: pain related to the tumour or its treatment
  • Chronic primary pain: fibromyalgia and some widespread pain syndromes

What Is Chronic Pain?

Chronic pain should not always be viewed simply as a symptom that has lasted longer than expected. In some patients it becomes a clinical problem in its own right.

Persistent pain can affect sleep, physical activity, work, relationships, mood and participation in everyday life.

This does not mean that chronic pain is “psychological”. Modern pain care recognises interactions between biological, psychological and social factors.

What Are Primary and Secondary Chronic Pain?

Chronic Primary Pain

Chronic primary pain occurs when no other condition adequately explains the pain or its impact and the pain itself becomes the main clinical problem. Fibromyalgia is one example.

Chronic Secondary Pain

Chronic secondary pain is related to an identifiable underlying condition such as osteoarthritis, cancer, neuropathy or inflammatory disease.

Primary and secondary chronic pain can coexist.

When Does Pain Need Urgent Assessment?

Prompt medical assessment is required for symptoms such as:

  • A sudden, unusually severe headache
  • Chest pain with breathlessness, sweating, nausea or faintness
  • New weakness, facial asymmetry or speech difficulty
  • Back pain with new loss of bladder or bowel control or numbness around the groin
  • Severe pain after significant trauma
  • Severe pain associated with high fever and systemic illness

How Is Pain Assessed?

Assessment considers the onset, duration, location, radiation, character and severity of pain, together with factors that aggravate or relieve it.

The clinician can also assess muscle strength, sensation, reflexes, sleep, physical function and the effect of pain on daily life.

Blood tests, X-rays, ultrasound, MRI, CT or nerve-conduction studies may be used when clinically indicated. Not every patient with chronic pain requires all of these investigations.

What Helps Pain?

There is no single treatment that works for every type of pain.

Depending on the diagnosis, treatment can include management of the underlying condition, medication, exercise, physiotherapy and rehabilitation, sleep management, pain-focused psychological therapies and selected interventional treatments.

How Is Chronic Pain Treated?

The goal of chronic pain treatment is not always complete elimination of pain. Improving mobility, sleep, daily function and quality of life are also important goals.

Management is generally individualised and multimodal.

For chronic primary pain, current guidance emphasises appropriately selected physical activity or exercise, pain-focused psychological therapies such as CBT or ACT, and individual assessment of medication options.

How Are Medicines Used for Pain?

Pain treatment should not automatically progress from a simple painkiller to increasingly strong medicines or morphine.

Medication should be selected according to the cause and mechanism of pain, age, comorbidities, other medicines and the expected balance of benefit and harm.

Paracetamol or non-steroidal anti-inflammatory medicines may be useful for some acute or secondary pain conditions, but they are not appropriate for every patient or every type of chronic pain.

Opioids are not routine first-line treatment for chronic non-cancer pain. When opioid therapy is considered, potential improvements in pain and function should be weighed against risks such as dependence, tolerance, sedation and overdose.

People already taking opioids, gabapentinoids, benzodiazepines or similar medicines should not stop them suddenly without medical advice.

How Is Neuropathic Pain Treated?

Neuropathic pain may not respond adequately to conventional analgesics.

Medicines such as amitriptyline, duloxetine, gabapentin or pregabalin can be considered in appropriate patients.

Some of these medicines are also used to treat depression or epilepsy, but their use for neuropathic pain does not mean that the patient necessarily has depression or epilepsy.

What Are Interventional Pain Treatments?

For selected patients, interventional techniques may be considered when a specific pain source can be targeted or other treatments provide insufficient benefit.

Depending on the diagnosis, these can include nerve blocks, selected epidural or regional injections, facet interventions, radiofrequency procedures and neuromodulation.

These procedures are not appropriate for every patient with chronic pain.

When Should You See a Pain Specialist?

A specialist pain assessment may be appropriate for pain lasting more than three months, pain that persists despite treatment, neuropathic pain, cancer-related pain, pain that substantially affects daily function or conditions that may require interventional treatment.

Chronic Pain Requires Individualised Assessment

Understanding the duration, cause, mechanism and impact of pain helps determine the appropriate combination of medication, rehabilitation, psychological approaches or interventional treatment.

Frequently Asked Questions

How long must pain last to be considered chronic?
Chronic pain is defined as pain that persists or recurs for more than three months. It can be related to an underlying condition, or in some people the pain itself can become the main clinical problem.
Can pain be psychological?
Pain should not be divided into simply physical or psychological categories. Pain is a personal experience influenced by biological, psychological and social factors. Psychological factors affecting pain do not mean that the pain is not real.
Can chronic pain completely disappear?
The outcome depends on the cause of the pain. Some pain conditions can resolve completely, while in others the goals include reducing pain, improving mobility and sleep and increasing daily function.
Does every patient with chronic pain need an MRI?
No. Imaging and other investigations are selected according to the location and duration of pain, examination findings and suspected cause. Routine MRI is not required for every chronic pain condition.
Are opioids the first treatment for chronic pain?
No. Opioids are not routine first-line treatment for chronic non-cancer pain. Treatment should be based on the cause and mechanism of pain, and potential opioid benefits should be weighed against possible harms.
Why are antidepressants sometimes used for pain?
Some antidepressant medicines affect pain-processing pathways and can be used for certain types of chronic primary or neuropathic pain. Being prescribed one of these medicines for pain does not necessarily mean that the person has depression.
When should someone see a pain specialist?
A pain specialist assessment may be appropriate for pain lasting more than three months, pain that persists despite treatment, neuropathic pain, pain that substantially affects daily life or conditions that may require interventional treatment.
Academic Hospital note: There is no single treatment suitable for every type of pain. Management should be individualised according to the cause, mechanism, duration and impact of pain on daily life. You can book an appointment.

References

  1. Academic Hospital. What Is Pain?
  2. International Association for the Study of Pain. IASP Announces Revised Definition of Pain
  3. International Association for the Study of Pain. Definitions of Chronic Pain Syndromes
  4. NICE. Chronic Pain: Assessment and Management of Chronic Primary Pain
  5. NICE. Neuropathic Pain in Adults: Pharmacological Management
  6. Centers for Disease Control and Prevention. Clinical Practice Guideline for Prescribing Opioids for Pain