Compared to acute pain, chronic pain usually lasts much longer (e.g., months or years).  In addition, chronic pain is not directly related to tissue damage.  In fact, sometimes no tissue damage is detected; or, if the damage can be observed, the pain remains even after the tissue has healed completely.

Chronic pain has been linked with numerous negative outcomes, especially functional outcomes, like limits in mobility and difficulties with the performance of daily activities. It has been further linked with reduced quality of life and poor health and mental health, including increased stress, anxiety, depression, and a higher risk of opioid dependence. 

Chronic pain is also very costly, both in terms of direct costs (e.g., doctor’s visits and medical treatments) and indirect costs (lost productivity, such as fewer hours worked or missed workdays).

People with certain conditions are more likely to experience chronic pain.  Some of the more common pain-related conditions are listed below.

• Fibromyalgia: Widespread pain and tenderness.
• Back pain: Symptoms depend on the cause (e.g., pain caused by strain vs. osteoporosis).
• Inflammatory bowel disease: Abdominal pain and discomfort.
• Headaches: Symptoms depend on the cause (e.g., migraine vs. cluster headaches).
• Rheumatoid arthritis: Joint pain and stiffness.

Chronic pain and its complex mechanisms

In chronic pain, the relationship between the experience of pain and the physical cause of pain is complex. 

One’s personal history, emotions, thoughts, present context, and behaviors can significantly modify the pain experience.  For example, fear, depression, the unwillingness to experience painful sensations, and the memory of pain might play a bigger part in the experience of chronic pain than do the physical sensations alone.

We may be able to understand chronic pain a little better by considering three potential mechanisms of pain: Nociception, neuropathy, and central sensitization.

Nociceptive pain occurs when nerve endings are stimulated (e.g., due to injury, inflammation), as can happen in some types of back pain. 

Neuropathic pain, in contrast, results from damage to the nervous system and the functioning of the nociceptive system (e.g., due to spinal cord injury, diabetic neuropathy).

The third mechanism, called central sensitization, refers to the fact that some repeated painful experiences cause the neurons in the spinal cord to become sensitized.  For instance, central sensitization may partly explain why 10-30% of individuals with rheumatic disorders (e.g., rheumatoid arthritis, osteoarthritis) develop fibromyalgia.  People with fibromyalgia tend to experience pain in many parts of their body, often in response to even mild pressure.  This heightened pain processing, which is not limited to one location, suggests the presence of central sensitization.

Given the complicated nature of chronic pain, the first step to treating pain is a full clinical evaluation, which gives the health provider the information needed to create a personalized treatment plan and select the interventions most likely to help.  These interventions might include a variety of surgical, pharmacological, behavioral, psychological, and complementary treatments (e.g., massage, biofeedback).