Chronic pain is a major cause of suffering, it interferes with daily routine work and often brings distress to the patients. In the International Classification of Diseases, chronic pain diagnoses were not depicted systematically. The lack of suitable codes use to hinder accurate epidemiological investigations and health policy decisions concerning chronic pain for example adequate finance to obtain multimodal pain management. An IASP Working Group along with WHO developed a classification system that is appropriate in wider contexts, like pain medicine, primary care, and low-resource environments.

Chronic pain is known as pain that lasts or recurs for more than 3 months. Pain can be an exclusive or a leading complaint which needs special treatment and care. Chronic pain may be rendered as a disease in its own right and in the study author's proposal this subgroup was called as “chronic primary pain in conditions like fibromyalgia or nonspecific low-back pain. In the other 6 subgroups, pain comes after an underlying disease: chronic cancer-related pain, chronic neuropathic pain, chronic secondary visceral pain, chronic posttraumatic and postsurgical pain, chronic secondary headache and orofacial pain, and chronic secondary musculoskeletal pain.

These conditions are reviewed as “chronic secondary pain” where pain may at least initially be devised as a symptom as per the study authors.