Counting your chickens before they hatch: improvements in an untreated chronic pain population, beyond regression to the mean and the placebo effect.

Introduction: Isolating the effect of an intervention from the natural course and fluctuations of a condition is a challenge in any clinical trial, particularly in the field of pain. Regression to the mean (RTM) may explain some of these observed fluctuations.

Objectives: In this paper, we describe and quantify the natural trajectory of questionnaire scores over time, based on initial scores.