by Michael D. Anestis, M.S.
Today's post covers a study published earlier this year in Archives of Suicide Research by Peggy Andover, Jennifer Primack, Brandon Gibb, and Carolyn Pepper. The authors noted that the vast majority of research on non-suicidal self-injury (NSSI) has been conducted on exclusively or predominantly female samples, as most believed that the behavior was substantially more common in women (e.g., Favazza & Conterio, 1989). That being said, recent research has indicated that men and women actually demonstrate comparable rates of NSSI in nonclinical samples (e.g., Anderson, Pepper, & Gibb, 2007; Hilt, Nock, Lloyd-Richardson, et al., 2008). This raises an important issue: if most of the research on NSSI has been conducted on females and men are self-injuring in nonclinical samples nearly as often, we might be unable to apply our knowledge from research to a large portion of individuals who self-injure. To address this, research that includes men is a necessity.
Along these lines, a recent study by Claes, Vandereycken, and Vertommen (2007) - whose work is frequently cited in just about every research project I conduct - found important differences between male and female psychiatric inpatients. In that study, men reported a greater number of NSSI episodes per day, more pain during the course of NSSI episodes, and less care of wounds than did women. Andover and her colleagues (2010) built upon this work by collecting from 103 undergraduate participants to examine potential sex differences in the prevalence, frequency, age of onset, methods, pain, sense of control, and degree of medical injury resulting from NSSI. 48 of those participants reported a history of NSSI, and the primary analyses - which are the ones we will discuss here - only involved those students.
So what did they find? First of all, men (n = 19) and women (n = 29) did not significantly differ in the number of lifetime episodes of NSSI (185.5 for women, 36.41 for men), average number of NSSI episodes per year (20.44 vs 6.26), engaging in NSSI within the past year (89.7% vs 84.2%), history of suicide attempts (27.6% v 21.1%), or the subjectively reported experience of pain during self-injury. You might notice that some of those numbers appear to represent large differences between men and women, but remember this is a very small sample size, which makes reaching statistical significance very difficult. It remains possible that, in a larger sample, at least some of those differences would be significant (although it is also possible that if data were collected on a larger number of participants, those apparent differences would even out and become more similar to one another).
Some of the results were, in fact, statistically significant. Women reported an earlier age of onset for NSSI and a greater medical injury at both the most recent and most severe NSSI episode. Women also exhibited a greater amount of variability in the average number of lifetime NSSI episodes, meaning that women vary in the degree to which they have engaged in NSSI much more so than men do. Although not quite statistically significant (p = .06), there was a trend indicating that men reported a greater sense of control over NSSI than did women. Men and women did not differ in the number of NSSI methods used; however, men were more likely to report burning behaviors and women were more likely to report cutting and scratching behaviors. For women, cutting and scratching were the most common methods whereas for men, self-hitting was the most common method.
So what does all of this mean? Based upon these data, it appears that there are some meaningful differences in NSSI between men and women in nonclinical populations. Although neither men nor women are more likely to self-injure, they do differ in the manner in which they do so, the age at which they first begin self-injuring, and the severity of the injuries. Obviously, these results need to be replicated before they can be seen as representing a pattern that generalizes across the population - preferably in a larger sample - but they are nonetheless very meaningful and represent an initial step into an under-researched area: NSSI in men.
In future studies, I'd love to see if the function of self-injury (e.g., to reduce negative affect versus to end dissociation) varies by sex and, if so, whether sex differences in pain during self-injury depend upon the function of the behavior (e.g., do individuals who self-injure to reduce negative emotions feel less pain during episodes while other groups do not differ from one another?). I would also like to see whether men and women who self-injure differ in physiological pain tolerance or whether the frequent use of a painful and provocative experience like NSSI washes out the typical sex differences on this front. Andover et al (2010) laid the groundwork for what could be some very interesting and influential future studies with both scientific and clinical implications.
What are your thoughts on this study? Are there things you would have done differently? Do you see specific implications for these findings? What would you like to see done next to help us further understand sex differences in NSSI?
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Mike Anestis is a doctoral candidate in the clinical psychology department at Florida State University and an incoming resident at the University of Mississippi Medical Center
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