The Gate Control Theory of controlling pain signals through gates is a major advance in understanding pain. Under the theory, the more open the gates are, the more pain or suffering. Alternatively, the more the gates are closed, the less pain and suffering is experienced, as illustrated in the Gate Control Theory image.
Of course, the important issue is what factors tend to open and close the gates. These can be divided into sensory, cognitive and emotional influences.
Factors that open the pain gates and cause more suffering include sensory factors, including such things as injury, inactivity, long-term narcotic use, and poor body mechanics. Cognitive factors include focusing on the pain, a lack of outside or pleasurable interests, worrying about the pain, and focusing on bad things associated with the pain. Emotional factors include depression, anger, anxiety, stress, frustration, hopelessness, and helplessness.
Factors that close the pain gates and cause less suffering include sensory factors including increasing activity, short-term use of pain medication, relaxation training, meditation, and aerobic exercise. Cognitive factors include outside interests, pain coping thoughts, and distracting from the pain. Emotional factors include having a positive attitude, decreasing depression, being reassured that the pain is not harmful, taking control of the pain, taking control of non-pain aspects of life, and stress management.
A simple sensory example of the gate process occurs when a person bangs his or her head on a cabinet corner, or strikes the “funny bone” in the elbow. This results in a fast-moving and “sharp” pain. However, when the area is rubbed, in an attempt to ease the pain, the nerve signal produced by the rubbing overrides the sharp pain and closes the spine gate. This results in the experience of less sharp pain (which has been replaced by the rubbing sensation). The same principle for closing the gates can be applied in the cognitive and emotional realms (as will be seen subsequently).
Although the Gate Control Theory explains many complicated findings related to pain, just a few examples include:
- Pain responses vary widely with the meaning of the situation in which it is experienced. Someone who experiences an injury in a life-or-death situation may barely notice the pain at that time; however, in a different situation, the same pain experience would result in excruciating pain.
- If pain is required for a desired goal, such as winning a game, getting a tattoo, or child-birth, the pain is much more bearable than a similar pain due to a negative occurrence such as an injury due to an accident or a serious medical condition.
- Chronic pain begins with some type of injury, but may continue long after the actual tissue damage from the injury is healed.
Pain Signals Travel at Different Speeds
In considering the Gate Control Theory, it is helpful to review the way pain signals work in the body:
- Fast pain signals, those using A-delta fibers, are crucial to protecting the body from injury. These nerve fibers send a quick message if a person touches something sharp, for instance. This type of pain is sometimes called "warning pain." While A-delta signals are felt quickly, they generally don't last long.
- Chronic pain messages move more slowly along C-fibers and the pain lingers longer. It is often described as aching, dull, cramping, burning, or nagging pain. This type of pain—called “reminder pain” for its role in ensuring that the brain is aware of the injury—feels worse than warning pain. It is the type of pain that can continue after the injury heals.
Both fast and slower pain messages use the same routes through the spinal cord, but their paths diverge in the brain.
Faster pain messages are sent to the brain's cortex, which is responsible for higher level thinking (see the “sensory” area in the previous image). Slower messages go to the parts of the brain that release stress hormones and handle emotions, the hypothalamus and the limbic system. The pathway of these slower messages is one factor in the role of stress, depression, and anxiety in chronic pain (see the “thoughts” and “feelings” areas in the previous image).