What is pain?

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, or described in terms of such damage. 1

Scientists and researchers around the world had to re-examine their beliefs about pain to reach this definition. They included the terms emotional and unpleasant to indicate that pain has an intense association with the sense of touch and also involves the limbic system and the cortex deep within the brain.1,2

Note that the definition of pain indicates that potential tissue damage can cause pain. This means there is no need for real tissue damage to occur for someone to feel real pain.
In fact, this definition indicates pain is produced in the brain, not in the tissues where sensation is experienced.1,2

About 30% of people worldwide suffer from chronic pain. The most common forms of pain include arthritis, headaches, stroke pain, neck pain, low back pain, facial pain, nerve pain, and cancer pain.3-6

 Common forms of pain4-6

  •  Arthritis pain
  •  Headache
  •  Stroke pain
  •  Neck pain
  •  Low back pain
  •  Facial pain
  •  Nerve pain
  •  Cancer pain

Tremendous advances in pain management have been made and many treatment options are available. However, many patients still suffer from chronic pain and do not receive adequate treatment. Patients need more detailed information to improve their understanding of chronic pain.4,6

How is pain generated?

Two different mechanisms can lead to the feeling of pain: nociceptive or neuropathic (nerve).

Nociceptive pain is caused by direct activation of pain fibers. This can be due to chemical, inflammatory, or mechanical stimulation. Neuropathic pain is pain that is generated or caused to continue by the nervous system.7

Nerve pain results after injury to the peripheral or central nervous system. It can be caused by trauma or disease that affects various nerves in the body. Nerve damage can be caused by physical injury (e.g., nerves are cut or experience a long period of continuous pressure), metabolic disorders (e.g., diabetes mellitus), poisonous substances (e.g., alcohol), viruses (e.g., shingles/herpes zoster), or inflammation. Low back pain with nerve pain can result when nerve roots are damaged by pressure of a slipped disc.8-10



  1. IASP. Available at: http://www.iasp-pain.org/Taxonomy?navItemNumber=576#Pain. Accessed 25 January, 2016.
  2. Arthritis & Chronic Pain Research Institute. The mechanics of chronic pain. Available at: http://www.pain-research.org/mechanics.html. Accessed 25 January, 2016.
  3. Elzahaf RA et al. The prevalence of chronic pain with an analysis of countries with a Human Development Index less than 0.9: a systematic review without meta-analysis. Curr Med Res Opin. 2012;28(7):1221-9.
  4. IASP. Unrelieved pain is a major global healthcare problem. Available at: http://www.efic.org/userfiles/Pain%20Global%20Healthcare%20Problem.pdf. Accessed 25 January, 2016.
  5. The American Academy of Pain Medicine. AAPM facts and figures on pain. Available at: http://www.painmed.org/patientcenter/facts_on_pain.aspx. Accessed 25 January 2016.
  6. Vellucci R. Heterogeneity of chronic pain. Clin Drug Investig. 2012;22;32 Suppl 1:3-10.
  7. Disorders of the nervous system. Available at: http://www.dartmouth.edu/~dons/part_2/chapter_19.html. Accessed 25 January, 2016.
  8. Baron R. Peripheral neuropathic pain: from mechanisms to symptoms. Clin J Pain. 2000;16(2 Suppl):S12-20.
  9. Ossipov MH, Porreca F. Challenges in the development of novel treatment strategies for neuropathic pain. NeuroRx. 2005; 2(4): 650-61.
  10. IASP. Guide to pain management in low-resource settings. A Kopf, NB Patel (Eds). Available at: http://www.iasp-pain.org/files/Content/ContentFolders/Publications2/FreeBooks/Guide_to_Pain_Management_in_Low-Resource_Settings.pdf. Accessed 25 January, 2016.
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