Defining pain: past, present, and future
The current definition of pain as per the IASP1 is
The proposed definition by Williams and Craig is as follows:
The proposed definition by Williams and Craig replaces the word “unpleasant” with “distressing” and I would caution against making this change. The Oxford dictionary defines the adjective distressing as “causing anxiety, sorrow or pain; upsetting.2” It is a vaguely defined state that includes pain itself, and although distress is often associated with pain, it is not always so. In the chronic pain setting, a goal of acceptance commitment therapy is to become more accepting of pain and reduce or eliminate the distress associated with it, and many patients achieve this. There are numerous examples of people in certain contexts, such as injured athletes and soldiers who are experiencing pain, but without distress, and are able to perform the task at hand to a very high level. Pain may even be associated with satisfaction in some circumstances, for example, the pain experienced in muscles and joints after achieving a significant physical feat such as climbing a mountain. Although the term “unpleasant” may not be ideal, it does convey the message that pain is generally a negative experience that is more applicable to the varying contexts in which pain occurs.
Williams and Craig have removed the phrase “or described in terms of such damage” and commented that the use of the word “describe” in particular prioritizes self-report above other ways that pain can be expressed to the detriment of people and animals who cannot self-report. However, this leaves their proposed definition stating that pain is associated with actual or potential tissue damage. This would exclude a large number of patients seen in the chronic pain clinic who are experiencing pain yet have no current or past evidence of tissue damage on clinical assessment. A revision of the definition of pain should remain applicable to this cohort of patients. Pain is our body's alarm system, and the alarm system can become dysfunctional. When we experience pain, we are perceiving actual or potential tissue damage, whether or not the threat of tissue damage exists. It is the perception of threat that is important to convey in the definition.
To better reflect the multidimensional nature of pain, Williams and Craig have expanded on the current definition that includes “sensory” and “emotional” to add “cognitive” and “social.” The term social is a word with complex meaning, relating to an individual's connection with other people, as well as society, and may not be well suited to a definition of pain. Describing the multidimensional nature of the pain experience with the more basic components of sensation, thoughts, feelings, and behaviors makes more sense. Pain is talked about in terms of a biopsychosocial framework, and the bidirectional relationship between pain, biomedical, psychological, and social factors is mediated through these basic components.
A revised definition of pain must be applicable to all forms of pain in all contexts, no matter how trivial or severe, and no matter what the underlying pathophysiology, of which although our understanding is continually advancing, is still in its infancy. Pain is defined as an experience, which requires consciousness. This experience is mediated by dynamic networks of neurons in the brain that produce electrochemical activity.