Understanding Pain

The fundamentals of pain

Pain is defined as an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.1 Pain has many dimensions and can vary in intensity, location in the body and duration of time. Depending on the type of pain, it can feel like throbbing, burning, shooting or tingling and can range in intensity from mild to severe.3,4 In addition to the physical impact, it can also have psychological, emotional and social effects on everyday life.3

Sometimes the cause of pain is obvious, such as from injury, and other times the source might come from an underlying condition. In some cases, it can be difficult to categorise the exact cause of pain.3

What happens in the body when we encounter a harmful stimulus?

Pain is a normal response to actual or potential injury to the body but can also occur without a clear cause:3,5,6

The three different mechanisms that can lead to the perception of pain: Harmful stimuli, Signal, Pain is felt

There are three different mechanisms that can lead to the perception of pain. In some cases, more than one mechanism may be involved.

1. Nociceptive pain

This type of pain is typically caused by damage to the body’s tissues from either injury or inflammation. Examples include:5,7,8

  • Sports injury
  • Arthritis
  • Appendicitis

2. Neuropathic pain

This type of pain is typically caused by damage to nerves. This damage can be due to lesions in the nervous system, diseases that affect the nerves or injury. Examples include:3,5,9

  • Peripheral neuropathic pain e.g., painful diabetic peripheral neuropathy, chemotherapy-induced neuropathy
  • Post-stroke pain
  • Spinal cord injury
  • Cancer-induced neuropathic pain

3. Nociplastic pain

This type of pain occurs without clear evidence of actual or threatened tissue damage or lesions and diseases of the nervous system. Examples include:10

  • Fibromyalgia
  • Complex regional pain syndrome
  • Non-specific back pain


What is the difference between acute and chronic pain?

Pain is complex and is not only classified by the mechanisms above, but also by severity, location in the body and duration.2 One of the most common ways to classify pain is by the duration of time someone has been experiencing pain:

Acute Pain Chronic Pain
Lasts for less than 3 months11 Lasts for longer than 3 months12
Occurs usually in response to tissue trauma and related inflammatory processes13 Can be due to an underlying disease such as cancer or arthritis3
Has no obvious cause5 or may continue after the original injury has healed3
Serves a useful and life sustaining (protective) function14 Typically serves no adaptive purpose5
Poorly controlled acute pain can be a factor leading towards chronic pain15 Influenced by a number of interconnected factors, including:13
Biological: genetics, age, sex, sleep, hormones and internal pain regulation systems
Psychological: poor sleep, anxiety or depression
Sociocultural: low educational attainment, culture and poor social support


In 2019 the IASP and the World Health Organization recognized chronic pain as a health condition in its own right13


Some of the most common types of chronic pain are:16

  • Migraine
  • Low back pain or lumbar pain
  • Neck pain
  • Musculoskeletal pain
  • Pain associated with osteoarthritis


Who is affected by chronic pain?

Chronic pain is an enormous global health problem17 and affects around 1 in 5 adults worldwide.18,19,20


What are some factors that can increase the likelihood of experiencing chronic pain?13,21,22,23

Factors that can increase the likelihood of experiencing chronic pain: Age

Chronic pain becomes more common with increasing age.21

Factors that can increase the likelihood of experiencing chronic pain: Sex

Women are more likely to report or experience chronic pain than men22 and report a higher level of pain intensity and higher pain-related disability than men23

Factors that can increase the likelihood of experiencing chronic pain: Sociocultural background

Chronic pain is associated with low educational attainment, culture and poor social support13

Pain is a dynamic consequence of a host of biological, psychological, and social factors; hence, guidelines have recommended interdisciplinary treatment, which ideally makes use of a personalised approach with a shared decision-making.13


The serious impact of chronic pain

Chronic pain exerts an enormous personal and economic burden, and it is considered to be one of the main causes of disability:13,19


Up to 90% of adults with chronic pain experience clinically significant insomnia24


of patients with chronic pain are less able or unable to do household chores25


of chronic pain patients have difficulty maintaining an independent lifestyle25


of patients with chronic pain have relationship difficulties25

Mental Wellbeing:

Chronic pain can have a significant impact on mental health and wellbeing.13 Research has shown that more than 50% of patients with chronic low back pain have depression and anxiety,26 and people suffering from chronic musculoskeletal pain with both depression and anxiety are likely to experience more severe pain and pain-related disability.27


The Economy:

The cost of chronic pain is significant:13,19,28,29



Chronic pain affects 1 in 3 Americans, costing up to $635 billion per year28


Across Europe, the cost of chronic pain is estimated to be as high as €300 billion


Chronic pain also increases the risk of other health problems and social exclusion.30


Chronic pain affects people’s ability to do their jobs effectively.

  • In the US, people with chronic pain worked 7.5 days less than those without chronic pain.31
  • In the EU, more than 50% of people are prevented from doing their work because of chronic pain.32
  • In the EU, chronic pain has substantial negative impacts on productivity at work.32

Having chronic pain may also affect employment. A survey revealed that less than 20% of people with chronic pain receive occupational rehabilitation in order to remain at work.32 Additionally, research in the UK found that chronic pain was present in 79% of those who were unable to work because of ill health and only in 40% of those in paid employment.33


  • References
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