Reactive effects of measurement of pain.

OBJECTIVE

Self-rating procedures that repeatedly focus the patient's attention on pain may change the experience of pain. This experiment was designed to determine whether repeated clinical pain measurement alters perceived pain intensity and distress.

PATIENTS AND SETTING

Fifty-four low-back-pain patients (26 men, 28 women) who were referred to, but had not yet attended, a back-care class in a teaching hospital.

DESIGN

Random assignment was made to one of three groups, each of which completed a different self-monitoring task daily for 8 days. Group 1 completed the McGill Pain Questionnaire; group 2 recorded their pain using a briefer pain diary; and group 3, a control group, kept a checklist of foods consumed, with no reference to pain. DEPENDENT MEASURES AND HYPOTHESES: Before and after the self-monitoring period, all three groups estimated their worst, least, and usual pain and their pain-related emotional distress, using visual analog scales. It was hypothesized that group 1 would produce the highest posttest ratings of pain and distress and group 3 the lowest.

RESULTS

Means on all four dependent measures were virtually identical across groups; analyses of covariance confirmed that none of the between-group differences approached significance.

CONCLUSIONS

The results suggest that daily self-monitoring of chronic clinical pain does not alter subjective pain intensity. Reactive effects of measurement that have been identified in studies of experimental and acute clinical pain probably take place on a much shorter time scale and thus may not be influential in daily measurement of long-term clinical pain.