What is Pain?

The International Association for the Study of Pain provides a practical definition of pain as, “an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.”¹Smith CB. Holland-Frei Cancer Medicine. John Wiley & Sons, 2017, Ch 46, p523.

From a clinical perspective, pain is far more than a distinct type of physical sensation. In the case of chronic pain, it can impact a patient’s overall physical, mental and emotional wellbeing.²Dueñas M et al. A review of chronic pain impact on patients, their social environment and the health care system. Journal of Pain Research, 28 June 2016, p457 Understanding pain and what causes pain are essential to its diagnosis and treatment.

What is the purpose of pain?

Both transient pain and acute pain have an apparent survival benefit. Rapidly pulling away from a burning object, for example, helps protect the body. Behaviors such as resting and immobilizing an injured extremity, such as a sprained ankle, may help promote natural healing and the restoration of normal function.³Hudspith MJ, Siddall PJ, Munglani R. Physiology of pain. In: Hemming HC, Hopkins PM, eds. Foundations of Anesthesia. 2nd ed. London, UK: Mosby; 2006. p267.

In contrast, chronic pain states have no clear protective or restorative value. Consequently, chronic pain is often considered indicative of sustained pathophysiology, provoked by inflammation or nerve injury.⁴Hudspith MJ, Siddall PJ, Munglani R. Physiology of pain. In: Hemming HC, Hopkins PM, eds. Foundations of Anesthesia. 2nd ed. London, UK: Mosby; 2006. p268

Acute vs. chronic pain

This section covers acute vs. chronic pain and includes definitions of nociceptive pain and neuropathic pain.

Other types of pain

Other types of pain described in this section include inflammatory pain, musculoskeletal pain, and visceral pain among others.