The differences in the ways that boys and girls are expected to react to pain has long been the subject of folk wisdom and cultural idioms: Boys are expected to “tough it out” and “take it like a man”, while expressions of pain in girls are accepted and sometimes even encouraged. But are societal expectations of how boys and girls should react to pain in line with the reported differences between boys and girls pain responses in the literature?
For a long time sex differences were ignored in pain research, and up until about 20 years ago many studies would only use male subjects, both in basic science animal research as well as human studies [1]. This is obviously a problem, and many areas of medical research (including pain) are catching on to this. Recently, a few large-scale systematic reviews of research in adults have been published showing that, when given exactly the same experimental pain task, women report experiencing more pain than men [2]. There is a lot of innovative research in the area of sex differences in pain, trying to understand what it is that drives these differences. In a recent review, Dr. Jeffrey Mogil outlines the numerous mechanisms that have been explored as potential explanations for how and why sex differences are present in pain, including biological (e.g., genetic, neurochemical, hormonal), psychological (e.g., catastrophizing, self-efficacy, coping), and sociocultural (e.g., gender roles) explanations, as well as a consideration of pain measurement issues [3]. Much of this research has been conducted with the hope that an understanding of sex differences may help us to personalize pain treatments. [4].
Despite all of this attention to sex differences among adults, we know very little about sex differences in children’s pain. One review reported that sex differences in pediatric chronic pain tend to emerge around the time of puberty, with adolescent girls having higher rates of chronic pain than adolescent boys [5]. Our team at the Centre for Pediatric Pain Research published a paper recently in PAIN that set out to see if the same were true of healthy children’s experiences of experimental pain. We did this by pooling the results of 33 different studies (with a total of 1069 girls and 1040 boys) to see if there were differences between boys and girls on a number of different measures of the pain experience [6].
We looked at the results separately for each different type of pain task. The first pain task we examined was the cold pressor task (CPT), which involves the child immersing their hand in a bath of cold water. We found that in studies using the CPT, girls rated their pain as being significantly higher than boys. However, this was only true in studies that were looking primarily at adolescents (i.e., the average age of children in the study was 12 years or higher).
Next we looked at tasks where pain was induced by applying heat to the skin. We found no differences between boys and girls on how painful they rated the task; however, we did find that boys could tolerate the pain for longer than girls. We also found that boys had a higher heat pain threshold, meaning that the temperature at which the heat was first reported to become painful was higher in boys than girls. Interestingly, when we looked at age groups separately, sex differences were only seen in the studies looking primarily at children (i.e., where the average age of participants was under 12 years).
Finally we looked at sex differences in experimental pressure pain, where a painful force is applied to part of the body. This test is not used very often in children, but with the studies that were available we found that there were no differences between boys and girls on their pressure pain threshold or how painful they reported the task to be.
The fact that we found that there were some differences between children (< 12 years) and adolescents (> 12 years) suggests that developmental factors (e.g., sex hormones that become present during puberty) may be involved in sex differences, but we need more research to investigate this further.
Additionally, it is important to remember that our findings were only looking at differences between sex groups. Beyond this, gender might also be important for understanding pain. ‘Gender’ refers to the attitudes and beliefs that a society promotes regarding what is considered acceptable or appropriate for males and females [7]. In pain, this may be things like how parents respond differently to their son’s pain than their daughter’s, or how children learn about what pain behaviours are appropriate for boys versus girls. This is an area we know very little about in pain research, particularly in children. In the future, it will be important to consider how these factors may influence children’s pain experiences.
About Katelynn Boerner
Katelynn Boerner is a PhD student in Clinical Psychology at Dalhousie University in Halifax, Nova Scotia, Canada. Her research is conducted at the Centre for Pediatric Pain Research in the IWK Health Centre, supervised by Dr. Christine Chambers. She received her BSc (Hons) in Psychology from the University of Ottawa in 2010. While conducting the research described above, Katelynn was supported by a doctoral award from the Canadian Institutes of Health Research (CIHR). She is also the 2014 winner of the CIHR Institute of Gender and Health Award for Excellence in Gender, Sex, and Health Research. Katelynn is a trainee member of Pain in Child Health: A Strategic Research Training Initiative of CIHR.
References
[1] Mogil, J.S. & Bailey, A.L. (2010). Sex and gender differences in pain and analgesia. In I. Savid (Ed.), Progress in Brain Research (pp. 141-157). Oxford, UK: Elsevier.
[2] Fillingim, R., King, C., Ribeiro-Dasilva, M., Rahim-Williams, B., & Riley, J. (2009). Sex, Gender, and Pain: A Review of Recent Clinical and Experimental Findings The Journal of Pain, 10 (5), 447-485 DOI: 10.1016/j.jpain.2008.12.001
[3] Mogil JS (2012). Sex differences in pain and pain inhibition: multiple explanations of a controversial phenomenon. Nature reviews. Neuroscience, 13 (12), 859-66 PMID: 23165262
[4] Niesters M, Dahan A, Kest B, Zacny J, Stijnen T, Aarts L, & Sarton E (2010). Do sex differences exist in opioid analgesia? A systematic review and meta-analysis of human experimental and clinical studies. Pain, 151 (1), 61-8 PMID: 20692097
[5] King S, Chambers CT, Huguet A, MacNevin RC, McGrath PJ, Parker L, & MacDonald AJ (2011). The epidemiology of chronic pain in children and adolescents revisited: a systematic review. Pain, 152 (12), 2729-38 PMID: 22078064
[6] Boerner KE, Birnie KA, Caes L, Schinkel M, & Chambers CT (2014). Sex differences in experimental pain among healthy children: a systematic review and meta-analysis. Pain, 155 (5), 983-93 PMID: 24508752
[7] World Health Organization. What do we mean by ‘‘sex’’ and ‘‘gender’’?