Pain begets pain. When marathon runners are not in pain anymore, they underestimate their memory of marathon pain--A mediation analysis

Placebo analgesia was produced by conditioning trials wherein heat induced experimental pain was surreptitiously reduced in order to test psychological factors of expectancy and desire for pain reduction as possible mediators of placebo analgesia. The magnitudes of placebo effects were assessed after these conditioning trials and during trials wherein stimulus intensities were reestablished to original baseline levels. In addition, analyses were made of the influence of these psychological factors on concurrently assessed pain and remembered pain intensities. Statistically reliable placebo effects on sensory and affective measures of pain were graded according to the extent of surreptitious lowering of stimulus strength during the manipulation trials, consistent with conditioning. However, all of these effects were strongly associated with expectancy but not desire for relief. These results show that although conditioning may be sufficient for placebo analgesia, it is likely to be mediated by expectancy. The results further demonstrated that placebo effects based on remembered pain were 3 to 4 times greater than those based on concurrently assessed placebo effects, primarily because baseline pain was remembered as being much more intense than it actually was. However, similar to concurrent placebo effects, remembered placebo effects were strongly associated with expected pain levels that occurred just after conditioning. Taken together, these results suggest that magnitudes of placebo effect are dependent on multiple factors, including conditioning, expectancy, and whether analgesia is assessed concurrently or retrospectively.

Twenty women who attended the author's natural childbirth classes between 1968 and 1974 were the informants in this study of long-term memories of their first childbirths. The data from each informant consisted of 1) a labor and birth questionnaire, including an open-ended account of her labor, written shortly after her baby was born; 2) a similar questionnaire and account written in 1988 and 1989; and 3) a transcribed interview during which her memories and perceptions were discussed and any discrepancies between the questionnaires were explored. The questionnaires were compared for consistency of recall, and the interviews consulted for further clarification. Specific memories were excerpted, compared, classified, tabulated, and summarized. Findings were that, years later, women's memories are generally accurate, and many are strikingly vivid, especially of onset of labor; rupture of the membranes; arrival at the hospital; actions of doctors, nurses, and partners; particular interventions; the birth; and first contact with the baby. Most memory lapses or confusion were minor. Evidence of a halo effect was observed as well.