Types and theories of pain

Pain: a sensory and/or emotional discomfort which tends to be associated with actual tissue damage or threatened tissue damage, including irritation.

Acute and chronic pain 

Acute pain: typically lasts between 3 to 6 months. People experience anxiety while the pain is there but it slowly disappears as the pain begins to dissipate. It considered to be relatively more sharp and severe as it is directly related to soft tissue damage.

Chronic pain: typically lasts more than 3 months and can become progressively worse and reoccur intermittently. People experience high levels of anxiety and develop a feeling of helplessness and depression since the pain does not dissipate. An example could be migraines.

Psychogenic pain
Any type of pain that refers to episodes where there is not organic cause for it but the person is still experiencing it. An example is phantom limb pain, which is a condition whereby a patient who is an amputee still experiences pain in the limb that has been removed or has no functioning nerves. It is often describes as a burning pain or cramp.

Melzack (1992) found that phantom limb is not only a case of pain, there are 5 other features related to it:

1. The phantom limb feeling real.
2. The phantom arm hanging down or swinging in coordination with the other.
3. The phantom limb getting stuck in awkward situations.
4. Feelings like the artificial limb is a glove.
5. Having the impression of pressure on the phantom limb.

Specificity theory 

The early model of pain, that predicted that we have a sensory system that is speficically dedicated to pain – a series of neurons form a pathway that leads to a dedicated pain centre in the brain. 

The more this pathway is used, the more intense is the pain experienced by the person ; therefore, according to this theory pain is purely physiological. Some psychologists believe there is evidence that certain fibres are exclusive to pain but sensory fibres on our skin can detect heat,cold and certain pressures too. This makes the exclusivity argument quite weak. 

Gate Control Theory 

MELZACK AND WALL (1965) proposed the idea that pain is detected and picked up by sensory signals but the spinal cord plays a key role in the experience of the actual pain. This has a mechanism in it that acts like a gate that is either open or closed. If the gate is open, pain will be felt, if it is closed pain will not be felt. This process is controlled by three main factors:

1. The amount of activity in pain fibres – the more harmful and noxious the pain stimulus is, the more likely the gate will be opened. 
2. The amount of activity in other peripheral fibres – these are called A -beta fibres and carry information about ‘low-level pain’. When there is activity in these, the gate tends to close as the pain stimulus is not dangerous.
3. Messages from the brain – information such as excitement and anxiety can affect how much the gate is opened or closed.

Sarafino (2006) noted conditions that can open or close the gate.

It can be opened by:

• Severe injury 
• Anxiety, worry, depression 
• Focusing too much on the pain, and having no distraction

It can be closed by:

• Medication 
• Positive emotions, relaxation, rest
• Distraction from the pain