The Effect of Past Pain Experiences on Future Pain Ratings

How accurate is memory recall for pain? Some studies say the level of remembered pain is accurate; others say pain recall is distorted. In this study researchers show that pain is exaggerated over time when it is linked with a negative emotion.

Healthy adults were exposed to temperatures cold enough to cause intense, acute pain. The pain was similar to an "ice cream headache." Saliva was collected before and after the experiment to measure cortisol levels. Cortisol is a hormone released when a person is having a painful experience. It can be used as a measure of stress.

Forty-three healthy adults were included in this study. Cortisol and pain levels were measured before, during, and after the painful stimulus. Mood was also tested before and right after. Follow-up testing of mood and memory or recall of pain levels were re-measured nine months later.

Subjects remembered the maximum pain intensity later as being greater than reported at the time of the pain. This is called post-exposure pain modulation. This study confirms that a negative experience (painful test) results in a heightened memory of pain later. If this cold test was done again, the memory of the first experience would lead to a higher pain rating the second time.

The authors conclude these findings may help in a clinical setting. Patients who have painful procedures may be able to reduce the pain when these procedures are repeated. For example using stress management techniques during bone marrow aspiration or spinal tap may reduce the initial perception of pain. Then future repeats of the same treatment may not be so painful. The same may be true for patients having other repeated painful events such as biopsy or radiation.