Understanding how pain is defined can be helpful in learning how to control it better. For the purposes of research and medical practice, pain is typically divided into three categories:

Acute Pain Usually Lasts a Short Time

Pain that lasts less than 3 to 6 months, or pain directly related to tissue damage, is called acute pain. This is the type of pain caused by a paper cut or needle prick. Other examples of acute pain include:

• Touching a hot stove or iron. This pain will cause a fast, immediate, intense pain with an almost simultaneous withdrawal of the body part being burned. A few seconds after the initial pain and withdrawal, another type of pain, more of an ache, is likely to be experienced.
• Smashing one's finger with a hammer. This pain is similar to that of touching a hot stove in that there is immediate pain, withdrawal, and then a “slower” aching pain.
• Labor pains. The pain during childbirth is acute and the cause is certainly identifiable.

When pain persists, it becomes more affected by other influences, which can increase the individual's risk of developing chronic pain. These influences include such things as the pain signal continuing to reach the central nervous system after the tissue has healed, lack of exercise (physical deconditioning), a person’s thoughts about the pain, as well as emotional states such as depression and anxiety.

Chronic Pain Continues After Tissue Heals

The term “chronic pain” is generally used to describe pain that lasts more than three to six months, or beyond the point of tissue healing. This type of pain might also be termed “chronic benign pain” or “chronic non-cancer pain,” depending upon the situation. (Chronic pain due to cancer is more of an acute or acute-recurrent type of pain since there is ongoing and identifiable tissue damage. There is also chronic pain due to an identifiable cause, which will be discussed subsequently). For the purposes of this discussion, the term “chronic pain” will be used.

Chronic pain is usually less directly related to identifiable tissue damage and structural problems. Chronic back pain without a clearly determined cause, failed back surgery syndrome (continued pain after the surgery has completely healed), and fibromyalgia are all examples of chronic pain. Chronic pain is much less well understood than acute pain.