There are many ways to classify pain. This can sometimes be confusing!
The sections below describe various types of pain in more detail. However, there are many other, less common types of pain that may not be discussed here. Talk to your health-care provider if you have any questions about the type of pain that affects you.
Duration, location and frequency of pain
Here are some of the different ways to classify, or categorize, pain.
Duration: Pain can be defined in terms of its duration (how long it lasts). Acute pain is brief, but chronic pain lasts a long time.
Location: Pain can also be defined by its location in the body or its link with an underlying disease, such as arthritic pain.
Frequency: Chronic pain can be described as persistent or recurrent.
- Persistent chronic pain is pain that lasts for six months on at least half the days of each month.
- Recurrent pain is pain that occurs in less than half of the days of each month.
Pain mechanisms
Mechanism: Pain can also be defined by the underlying mechanism or what causes it. Two main mechanisms cause pain.
- Nociceptive pain occurs when pain messages are sent to your nerves and brain by receptors in your tissues (such as an organ or your hands or feet).
- Neuropathic pain occurs when pain messages are created by nerves in your body or the receiving centre in the brain.
Many people with chronic pain have a combination of both nociceptive and neuropathic pain—this is called mixed pain.
Gate control theory of pain
We used to think that the amount of pain someone felt matched the amount of damage to tissues. Now, thanks to the gate control theory of pain, we know that is not the case.
The gate control theory proposes that a complex “gating system” in the spinal cord controls the strength of pain signal that travels from the site of an injury to the brain.
The circuit works like a gate that opens or closes. How much the gate opens depends on a number of factors, including signals that arrive there from the brain. The more the gate opens, the stronger the pain signal that gets through and the more pain someone will experience.
The signals from the brain can be affected by a range of internal and external factors.
- Internal factors include your emotions (stress or anxiety, feeling happy or sad), your thoughts, your physical health (exercise, sedentary time), your behaviour and your previous experiences with pain.
- External factors include your responsibilities at work or school and your relationships.
Together, all these factors can make your pain better or worse.
Summary of acute and chronic pain
Taking these key terms into account, here is a summary of how acute pain and chronic pain differ from each other.
| Feature | Acute pain | Chronic pain |
|---|---|---|
| Cause | Usually a single obvious cause such as a vaso-occlusive pain episode or tissue damage due to surgery | Usually multiple causes or triggers |
| Mechanism | Nociceptive and/or neuropathic pain | Nociceptive, neuropathic or mixed pain |
| Purpose | Protective: regulates the body's actions and healing | No protective function or purpose |
| Duration | Short-lived (days to weeks) | Occurring on over half of the days each month for at least six months |
| Intensity | Usually in line with severity of the injury (the more severe the injury, the greater the pain) | Often out of proportion to the physical injury (pain can exist when injury is healed) |
| Treatment | Usually treated with pharmacological and psychological therapies | More difficult to treat, requiring multiple approaches |
| Outcome | Expected to get better with healing | Often continues over time and must be managed |
