Elsevier

Psychiatry Research

Volume 220, Issue 3, 30 December 2014, Pages 921-926
Psychiatry Research

Pain analgesia among adolescent self-injurers

https://doi.org/10.1016/j.psychres.2014.08.016Get rights and content

Abstract

Although non-suicidal self-injury (NSSI) involves self-inflicted physical harm, many self-injurers report feeling little or no pain during the act. Here we test: (1) whether the pain analgesia effects observed among adult self-injurers are also present among adolescents, and (2) three potential explanatory models proposing that habituation, dissociation, and/or self-criticism help explain the association between NSSI and pain analgesia among adolescents. Participants were 79 adolescents (12–19 years) recruited from the community who took part in a laboratory-based pain study. Results revealed that adolescent self-injurers have a higher pain threshold and greater pain endurance than non-injurers. Statistical mediation models revealed that the habituation and dissociation models were not supported; however, a self-critical style does mediate the association between NSSI and pain analgesia. The present findings extend earlier work by highlighting that a self-critical style may help to explain why self-injurers exhibit pain analgesia. Specifically, the tendency to experience self-critical thoughts in response to stressful events may represent a third variable that increases the likelihood of both NSSI and pain analgesia. Prospective experimental studies are needed to replicate and tease apart the direction of these associations, and may provide valuable leads in the development of effective treatments for this dangerous behavior problem.

Introduction

Non-suicidal self-injury (NSSI) is a dangerous behavior problem that involves intentional damage to one׳s own body tissue in the absence of any intent to die. Engagement in NSSI is disturbingly common among adolescents with prevalence rates estimated at 13–23% in community samples (Jacobson and Gould, 2007). In addition to the inherent physical damage caused by NSSI, this behavior also has been found to be related to increased rates of suicide attempts (Nock et al., 2006), as well as depression, drug abuse, and disordered eating (Hilt et al., 2008). Despite its frequency and potential for serious harm, many fundamental aspects of NSSI are not well understood.

Although NSSI, by definition, involves hurting oneself, as many as 50% of adult self-injurers (Leibenluft et al., 1987) and 80% of adolescent self-injurers (Nock et al., 2006) report feeling little or no pain while engaging in the act. Consistent with these self-reports indicating reduced sensitivity to pain, prior laboratory studies have shown that adult self-injurers exhibit pain analgesia compared to non-injurers (Kemperman et al., 1997a, Russ et al., 1999, Bohus et al., 2000, Hooley et al., 2010, McCoy et al., 2010, Franklin et al., 2011, Franklin et al., 2012), in that they (1) take longer to identify a sensation as painful (i.e., pain threshold), and (2) are willing to tolerate the pain for a longer period of time (i.e., pain endurance). Despite these findings, it is not yet known whether this pain analgesia is present during adolescence. Recent research has revealed that related constructs such as depression (Kaufman et al., 2001) and reward sensitivity (Steinberg, 2008) differ in adolescents relative to adults, and it is possible that pain sensitivity does as well. In addition, the experience of pain may change over time as a result of self-injury. One prior study suggested that the discontinuation of NSSI may be associated with normalization of pain perception and decrease in the pain analgesic effect (Ludäscher et al., 2009). Understanding the developmental course of pain analgesia among self-injurers is crucial both to our basic understanding of NSSI and to identifying potential targets for early intervention.

Another major unknown is why those engaging in self-injury experience this pain analgesia. Several explanations have been proposed. First, it is possible that pain analgesia results from a process of habituation through repeated exposure to painful stimuli. Specifically, past experiences with self-harm, including NSSI, may lead to decreased sensitivity to pain over time. In support of this theory, prior studies have found that adult self-injurers with longer histories of NSSI reported feeling less pain when engaging in the act (Claes et al., 2006) and had higher pain threshold (Hooley et al., 2010) and pain endurance (St. Germain and Hooley, 2013). However, Nock et al. (2006) found that adolescent inpatients who reported no pain during NSSI actually had fewer past NSSI episodes. As these findings underscore, evidence of a link between frequency of past NSSI and pain analgesia is mixed. As such, we tested the role of habituation by examining whether the frequency and duration of NSSI is associated with an objective measure of pain analgesia.

Second, it is possible that dissociation mediates the association between NSSI and pain analgesia. Self-injurers frequently report experiencing dissociative states (e.g., Kemperman et al., 1997b), and it is possible that the experience of dissociation alters pain perception. This relationship between NSSI and pain sensitivity may be explained in different causal directions: physical pain may serve as a means to reduce unpleasant dissociative feelings (Brown et al., 2002), or dissociative symptoms may mask the sensation of pain, rendering the physical sensation less salient (Brodsky et al., 1995). Although not examining self-injurers specifically, Ludäscher et al. (2007) found that individuals with reduced pain perception tended to have greater self-reported dissociative symptoms. However, Hooley et al. (2010) reported no association between dissociation and pain perception in a sample containing adult NSSI and control participants. Even so, both pain analgesia and dissociation are common to NSSI and it is plausible there may be an association between the two constructs.

Third, it may be that self-criticism serves a mediating role in the relation between NSSI and pain analgesia. That is, negative beliefs about oneself may result in greater willingness to endure pain, perhaps due to a view of the experience of pain as congruent with oneself. Recent research has shown that people who engage in NSSI are more self-critical than people who mistreat themselves in other, more indirect ways (St. Germain and Hooley, 2012), and that self-criticism (Hooley et al., 2010) and emotion dysregulation (Franklin et al., 2012) are associated with greater pain endurance. Furthermore, Bastian et al., (2011) found that participants who performed a guilt-inducing exercise (thereby increasing self-criticism) prior to engaging in a pain task tolerated pain longer and showed a greater reduction in guilt, suggesting that the pain may act as negative reinforcement for self-criticism. As has been suggested by Hooley (see Hooley et al., 2010, St. Germain and Hooley, 2012), people who are highly self-critical may regard pain as something they deserve, allowing self-injury to assume a self-punishing or guilt-reducing function. These results suggest the intuitive association between self-criticism and pain endurance in that self-injurers are experiencing pain and choosing to endure it. There is less support theoretically and empirically, however, for the association between self-criticism and pain threshold, or the idea that more self-critical individuals are not experiencing pain to the same intensity (Hooley et al., 2010).

Although self-criticism may play a crucial role in reducing some of the barriers to self-injury (e.g., pain), recent research suggests that NSSI may serve the function of reducing negative affect and increasing positive affect more generally, rather than being limited to certain kinds of emotional experiences (e.g., self-criticism, guilt). Franklin et al. (2013) have proposed pain offset relief (i.e., the simultaneous positive and negative reinforcement resulting from the removal of pain) as a possible mechanism by which such affective reinforcement occurs. Individuals, perhaps motivated to engage in NSSI by self-criticism and/or willingness to endure pain, incidentally derive the natural physiological benefit of pain offset relief (Franklin et al., 2013).

The purpose of the current study was to examine whether the pain analgesic effect observed among adult self-injurers also is seen among adolescent self-injurers. Our main hypothesis was that adolescent self-injurers would exhibit greater pain analgesia (i.e., decreased sensitivity to pain, and greater willingness to endure pain) relative to adolescent non-injurers. In addition, we tested these three potential explanations for the association between self-injury and pain analgesia in adolescent self-injurers.

Section snippets

Participants

Participants were 79 (63 female) adolescents and young adults ages 12–19 years (M=17.34, S.D.=1.79). Fifty-eight reported a history of NSSI and 21 were non-injurious controls. We focused on adolescence and young adulthood because of the increased risk for self-injurious thoughts and behaviors during this developmental period (Nock et al., 2008). Participants self-identified as European American (75.9%), Hispanic (7.6%), Asian American (3.8%), African American (2.5%), and other (10.1%). NSSI and

Preliminary analyses

The NSSI group had higher rates of mood disorders (46.6%) compared to the control group (4.8%), χ2(1, N=79)=11.77, p=0.001, and higher rates of anxiety disorders (58.6%) than the control group (19.0%), χ2(1, N=79)=9.67, p=0.002. No significant group differences were found for alcohol and substance use disorders, externalizing disorders, and eating disorders, or total number of psychiatric disorders.

Main analyses

Analyses revealed that adolescent self-injurers (n=58) had higher pain thresholds (M=59.6 s,

Discussion

The primary aim of the current study was to test whether adolescent self-injurers exhibit pain analgesic effects similar to those observed previously among adult self-injurers in order to better understand the developmental trajectory of NSSI. As hypothesized, results revealed that community adolescent self-injurers have a higher pain threshold and pain endurance than do non-injurers. Post-hoc analyses suggest that higher rates of mood and anxiety disorders among the NSSI group did not account

Acknowledgment

We are grateful to members of the Laboratory for Clinical and Developmental Research at Harvard University. This research was supported by grants from the William F. Milton Fund and William A. Talley Fund of Harvard University, and the John D. and Catherine T. MacArthur Foundation.

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