Skip to Content

Chronic Pain


James C. Watson

, MD, Mayo Clinic College of Medicine and Science

Last full review/revision Apr 2020| Content last modified Apr 2020

Chronic pain is pain that lasts or recurs for months or years.

Usually, pain is considered chronic if it does one of the following:

  • Lasts for more than 3 months
  • Lasts for more than 1 month after the injury or disorder that originally caused pain has resolved
  • Recurs off and on for months or years
  • Is associated with a chronic disorder (such as cancer, arthritis, diabetes, or fibromyalgia) or an injury that does not heal

(See also Overview of Pain.)

Chronic pain can make the nervous system more sensitive to pain. For example, chronic pain repeatedly stimulates the nerve fibers and cells that detect, send, and receive pain signals. Repeated stimulation can change the structure of nerve fibers and cells (called remodeling) or make them more active. As a result, pain may result from stimulation that might not ordinarily be painful, or painful stimuli may seem more severe. This effect is called sensitization.

Also, areas of muscle or connective tissue may become very sensitive and tender to the touch. These areas are called trigger points because touching these areas frequently triggers unexplained pain that radiates to other areas of the body.

Did You Know...

  • Chronic pain can physically change the nervous system in ways that make the pain worse and last longer.

Chronic disorders (such as cancer, arthritis, diabetes, or fibromyalgia) can cause chronic pain. Chronic pain can also result from an injury, even a mild injury if nerve fibers and cells have become sensitized.

Anxiety and other psychologic factors may help explain why some people experience pain as more unpleasant than others do and why pain limits their activities more. For example, people with chronic pain know it will recur and may become fearful and anxious as they anticipate the pain. Fear and anxiety can reduce the production of substances that reduce the sensitivity of nerve cells to pain. These changes in sensitivity to pain partly account for pain that persists after its cause resolves and for pain that feels more severe than expected.

Other factors may also influence pain perception. If people have to continually prove that they are sick to obtain medical care, insurance coverage, or time off from work, they may unconsciously exaggerate their perception of pain. This response differs from malingering, which is conscious exaggeration of symptoms to obtain a benefit. Family members and friends may unwittingly reinforce the person's perception of pain by constantly asking how the person feels or by doing things for the person.

Sometimes what originally caused the pain is obvious—for example, when people have had an injury that resulted in chronic back pain. Or the cause may be unknown—for example, when people have a chronic headache.

Symptoms of Chronic Pain

People with chronic pain often feel tired, have problems sleeping, lose their appetite and/or taste for food, and lose weight. They may become constipated, and their sex drive may decrease. These problems develop gradually. Constant pain can prevent people from doing what they usually enjoy. They may become depressed and anxious. They may stop their activities, withdraw socially, and become preoccupied with physical health.

Breakthrough pain is a brief, often severe flare-up of pain that may occur during treatment for chronic pain. It is called breakthrough pain because it occurs despite treatment that has been regularly scheduled and is intended to control pain. Breakthrough pain may differ from person to person and is often unpredictable.

Diagnosis of Chronic Pain

  • A doctor's evaluation
  • Sometimes a mental health evaluation

Doctors thoroughly evaluate the person to identify the cause of pain and its effect on daily life. If no cause is identified, doctors then focus on relieving pain and helping the person function better.

Doctors ask the person whether the person feels depressed, has anxiety about the pain, and is sleeping well. Identifying these symptoms is critical because they can make the pain worse and, if present, must be treated if the pain is to be effectively treated. A formal mental health evaluation may be necessary.

Treatment of Chronic Pain

  • Drugs to relieve pain
  • Physical methods (such as physical therapy)
  • Psychologic and behavioral therapy

If a cause of chronic pain is identified, it is treated.

Treatment of chronic pain may include the following:

  • Drugs to relieve pain (analgesics)
  • Physical methods, such as physical therapy or occupational therapy
  • Complementary and integrative pain-relieving techniques, such as acupuncture, massage, and transcutaneous electrical nerve stimulation (TENS)
  • Psychologic and behavioral therapy

If treatments are ineffective, doctors may refer people to a pain clinic.


Depending on the severity of the pain, the following types of drugs may be used to treat chronic pain:

  • Nonsteroidal anti-inflammatory drugs (NSAIDs)
  • Opioid analgesics
  • Drugs called adjuvant analgesics (such as antidepressants or antiseizure drugs)

In most people taking pain relievers (analgesics) for chronic pain, the pain's intensity varies throughout the day. Intensity varies for several reasons, such as the following:

  • The characteristics of the affected nerves (for example, how quickly they send signals and where the nerves are located)
  • Activities that can cause pain (such as moving or touching the affected area)
  • Psychologic stress
  • Changes in the blood levels of pain relievers

To make sure that blood levels of pain relievers do not become too low, doctors may change the doses and the times these drugs are taken.

Combinations of drugs usually relieve pain more effectively than a single drug.

Opioids are used most often to treat moderate to severe pain due to cancer or to other disorders that shorten lifespan (terminal disorders). Opioids are also used as part of hospice care. Opioids are sometimes underused in people in these situations, resulting in needless pain and suffering.

Opioids may be underused because doctors

However, in people with pain due to cancer or another terminal disorder, concerns about side effects should not limit the use of opioids because side effects can usually be prevented or managed, and addiction is less of a concern.

Experts have recently revised the guidelines about how opioids should be used to treat chronic pain due to disorders that are not cancer and that do not shorten lifespan. The reason for this change is increasing awareness of opioid side effects, including an opioid use disorder (addiction), slowing of breathing (respiratory depression), and death due to overdose. As a result, doctors usually prescribe nondrug treatments (such as physical therapy) and nonopioid analgesics (such as NSAIDs and adjuvant analgesics) rather than opioids for people with one of these disorders.

However, for moderate to severe pain due to these disorders, doctors may consider opioids if all of the following are present:

  • The pain persists despite the use of other therapies and drugs.
  • The pain interferes with daily activities.
  • The benefits outweigh the risks.
  • The person is likely to return to the doctor's office for regular follow-up and monitoring while taking opioids

When deciding whether to use opioids for pain due to a disorder that is not cancer and does not shorten lifespan, doctors also consider how pain due to such a disorder is usually treated and whether other treatments may help. Guidelines are available to help doctors decide whether or not opioid therapy is appropriate.

Before prescribing opioids for any type of chronic pain, doctors ask the person questions to determine the following:

  • Whether the person is likely to misuse or abuse the drug—for example, whether the person has a history of alcohol or drug abuse or has or has had a major psychiatric disorder, such as depression
  • Whether the person is taking other drugs that may increase the risk of taking an opioid (such as antianxiety drugs or sleep aids)
  • Whether the person is likely to have side effects from an opioid (such as drowsiness, nausea, or an increased risk of falling)
  • Whether the person is likely to use the drugs for other purposes (for example, to sell them)

Opioids are usually used with other treatments, including nondrug treatments such as physical treatments and psychologic therapy.

When doctors prescribe an opioid for chronic pain, they typically give the person written information that describes the risks of taking opioids. They also ask the person to sign an agreement that specifies conditions required for opioid use, such as any special monitoring that may be needed. For example, doctors may periodically test the person's urine to determine whether the drug is being taken correctly, and they typically restrict the person to a single pharmacy for filling opioid prescriptions.

Doctors may refer people to a pain clinic or a mental health care practitioner who has expertise in substance abuse if the risk of having a problem is high. For example, people who have had an addiction usually need a referral.

Doctors explain the risks and side effects of opioids. People are advised

  • Not to drink alcohol or take antianxiety drugs or sleep aids when taking the opioid
  • To take the recommended dose at the recommended times and not to change the dose
  • To store the opioid in a safe, secure place
  • Not to share the opioid with anyone
  • To contact their doctor if the drug makes them drowsy or they have any other side effects (such as confusion, constipation, or nausea)
  • To dispose of unused pills as directed
  • To keep naloxone (an opioid antidote) on hand and to learn and teach family members how to administer it if an opioid overdose occurs

During treatment with opioids, doctors regularly evaluate how effective the drug is, whether it helps people function better, and whether side effects occur. Many people decide that they cannot tolerate the side effects of opioids or that the amount of relief the drugs provide does not justify continuing to take them. Opioids provide long-term relief for only some people who are treated with them, and usually, they only partially relieve the pain.

Opioids are typically taken by mouth or through a patch placed on the skin. If needed, they can be given by injection into a vein, a muscle, or directly into the space around the spinal cord through a pump. When given in these ways, opioids are usually given in a hospital or doctor's office.

Antidepressants and psychologic therapy are used to treat depression, if present.

Physical methods

Physical or occupational therapists use various techniques to try to relieve chronic pain and help people function better. If trigger points are present, practitioners may use a spray to cool the area, then stretch the muscle. This method (called stretch and spray) can help lessen pain. Wearing an orthosis (a device that supports damaged joints, ligaments, tendons, muscles, and bones) helps some people.

Sometimes doing exercises or increasing activity level helps. For example, walking regularly can help relieve lower back pain more effectively than resting in bed.

Physical therapists and occupational therapists can help people with chronic pain find ways to do their daily activities with less pain.

Integrative medicine

Integrative medicine (previously called complementary alternative medicine) may be used to treat chronic pain. For example, doctors may suggest acupuncture, mind-body techniques (such as meditation, yoga, and tai chi), manipulation and body-based therapies (such as chiropractic or osteopathic manipulation and massage therapy), and energy-based therapies (such as therapeutic touch and Reiki).

Psychologic and behavioral therapy

Various psychologic techniques (such as relaxation training, distraction techniques, hypnosis, and biofeedback) can sometimes help control pain. Distraction techniques may involve guided imagery. For example, people may be instructed to imagine a scene that is calming and comforting, such as resting on a beach or lying in a hammock.

Behavioral therapy can help people function better, even if it does not reduce pain. Doctors may recommend specific ways to gradually increase physical and social activities. People are advised not to let pain derail their commitment to better functioning. When this approach is used, many people report a decrease in pain. Doctors applaud progress, encourage people to continue improving, and continue to treat the pain as needed.

Doctors may also talk with family members or fellow workers to discourage them from doing anything that keeps the person focused on the pain. For example, they should not constantly ask about the person's health or insist that the person do no chores.

Pain rehabilitation programs

Doctors may recommend a pain rehabilitation program for people with chronic pain. These programs are managed by an interdisciplinary team, that includes psychologists, physical therapists, doctors, nurses, and sometimes occupational therapists and integrative medicine practitioners. The programs include education. cognitive-behavioral therapy, physical therapy, simplification of the drug regimen, and sometimes gradually decreased use of a pain reliever. They focus on the following:

  • Restoring function
  • Improving quality of life
  • Helping people control their own life, despite their chronic pain

Drugs Mentioned In This Article

Generic Name Select Brand Names
naloxone EVZIO

Copyright © 2022 Merck & Co., Inc., known as MSD outside of the US, Kenilworth, New Jersey, USA. All rights reserved. Merck Manual Disclaimer