Chronic pain (sometimes known as long-term pain or persistent pain) is pain that lasts for more than 3 months. Pain can be secondary to (caused by) an underlying condition (for example, osteoarthritis, rheumatoid arthritis, ulcerative colitis, endometriosis). Chronic pain can also be primary. Chronic primary pain has no clear underlying condition or the pain (or its impact) appears to be out of proportion to any observable injury or disease. The decisions about the search for any injury or disease that may be causing the pain, and about whether the pain or its impact are out of proportion to any identified injury or disease, are matters for clinical judgement in discussion with the patient. The mechanisms underlying chronic primary pain are only partially understood and the definitions are fairly new. All forms of pain can cause distress and disability, but these features are particularly prominent in presentations of chronic primary pain. This guideline is consistent with the ICD-11 definition of chronic primary pain.
ICD-11 gives examples of chronic primary pain, including fibromyalgia (chronic widespread pain), complex regional pain syndrome, chronic primary headache and orofacial pain, chronic primary visceral pain and chronic primary musculoskeletal pain. These specific conditions were used as search terms for the evidence underpinning the recommendations in this guideline, along with more general terms that describe studies in chronic pain populations. Categorisations may change with time and advances in understanding of disease mechanisms.
Section 1.1 of this guideline covers assessment for people living with all types of chronic pain (chronic primary pain, chronic secondary pain, or both). The experience of pain is always influenced by social factors (including deprivation, isolation, lack of access to services), emotional factors (including anxiety, distress, previous trauma), expectations and beliefs, mental health (including depression and post-traumatic stress disorder) and biological factors. When assessing chronic primary pain and chronic secondary pain, these potential contributors to the presentation should be considered.
Section 1.2 of this guideline contains recommendations for managing chronic primary pain. Recommendations for managing chronic secondary pain can be found in the NICE guidelines for those conditions. Diagnostic categories may overlap and primary and secondary pain conditions may coexist. In these cases, management should be guided by both this guideline and the NICE guideline for the secondary pain condition.
In the UK the prevalence of chronic pain is uncertain, but appears common, affecting perhaps one‑third to one‑half of the population. It is not known what proportion of people with chronic pain either need or wish for treatment. The prevalence of chronic primary pain is unknown, but is estimated to be between 1% and 6% in England.