Pain, Please: An Investigation of Sampling Bias in Pain Research

Abstract

Experimental pain research frequently relies on the recruitment of volunteers. However, because experimental pain research often involves unpleasant and painful sensations, it may be especially susceptible to sampling bias. That is, volunteers in experimental pain research might differ from nonvolunteers on several relevant variables that could affect the generalizability and external validity of the research. We conducted 2 studies to investigate potential sampling bias in experimental pain research. In study 1 we assessed participants' (N = 275; age = 17-30 years) perceived likelihood of participating in pain research. Pain catastrophizing, fear of pain, illness and injury sensitivity, depression, anxiety, sensation-seeking, gender identity, body appreciation, and social desirability were also assessed as potential predictors of the likelihood to participate. In study 2, participants (N = 87; Age = 18-31 years) could sign up for 2 nearly identical studies, with only one involving painful sensations. Thirty-six participants signed up for the pain study and 51 participants signed up for the no-pain study. Study 1 showed that lower levels of fear of pain, higher levels of sensation-seeking, and older age predicted the perceived likelihood of participating in pain research. Study 2 showed significantly higher levels of sensation-seeking in participants who signed up for the pain study compared with those who signed up for the no-pain study. The implications of these findings for future research, as well as the clinical conclusions on the basis of experimental pain research, are discussed.

Perspective: Intention to participate in experimental pain research was associated with less fear of pain, higher sensation-seeking, and older age. Actual participation in experimental pain research was associated with higher sensation-seeking. This potential sampling bias in studies involving painful stimuli could limit external validity and generalizability of pain research.

Keywords: Pain research; external validity; generalizability; sampling bias; volunteer bias.