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| Variation in NSSI - Identification and Features of Latent Classes in a College Population of Emerging Adults, ♥ ... |
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[ Pobierz całość w formacie PDF ] Journal of Clinical Child & Adolescent Psychology, 37(4), 725–735, 2008 Copyright # Taylor & Francis Group, LLC ISSN: 1537-4416 print = 1537-4424 online DOI: 10.1080/15374410802359734 Variation in Nonsuicidal Self-Injury: Identification and Features of Latent Classes in a College Population of Emerging Adults Janis Whitlock Family Life Development Center and Department of Human Development, Cornell University Jennifer Muehlenkamp Department of Psychology, University of North Dakota John Eckenrode Family Life Development Center and Department of Human Development, Cornell University Prior studies of nonsuicidal self-injury (NSSI) suggest the existence of multiple NSSI typologies. Using data from 2,101 university students, this study employed latent class analysis to investigate NSSI typologies. Results show a good fitting 3-class solution with distinct quantitative and qualitative differences. Class 1 was composed largely of women using 1 form to engage in superficial tissue damage with moderate ( < 11) lifetime inci- dents. Class 2 was composed predominately of men using 1 to 3 forms to engage in self-battery and light tissue damage, with low (2–10) lifetime incidents. Class 3 was com- posed largely of women using more than 3 self-injury forms and engaging in behaviors with the potential for a high degree of tissue damage with moderate to high numbers of lifetime incidents. All 3 classes were at elevated risk for adverse conditions when com- pared to no-NSSI respondents. We conclude that NSSI typologies exist and may war- rant differential clinical assessment and treatment. Awareness of nonsuicidal self-injury (NSSI; the deliber- ate destruction of body tissue without suicidal intent) in clinical and nonclinical populations is increasing. As a result, clinicians and first responders in community settings, such as secondary school teachers, counselors, social workers, and nurses, report increasing contact with individuals who engage in NSSI but little or no formal training in NSSI treatment (Heath, Toste, & Beettam, 2006; Whitlock, Eells, Cummings, & Purington, 2007). The need to better understand and treat NSSI has led to the empirical study of prevalence and correlates of NSSI in both clinical and nonclinical samples. A growing body of research shows NSSI to be common in contemporary adolescent and emerging adult populations, with rates from studies of commun- ity adolescents estimated at between 10% and 15% (Hawton & Rodham, 2006; Laye-Gindhu & Schonert- Reichl, 2005; Muehlenkamp & Gutierrez, 2004; Ross & Heath, 2002) and from college samples ranging from 17% to 35% (Gratz, 2001; Whitlock, Eckenrode, & Silverman, 2006). Despite the growing convergence around NSSI prevalence, there remain important differences across This research was supported by Cornell University’s School of Human Ecology Seed and Innovation Grant fund. We thank Amanda Purington for her support with all phases of the study. The statements and opinions expressed are the authors and not a reflection of the study’s funder. Correspondence should be addressed to Janis Whitlock, Family Life Development Center, Beebe Hall, Cornell University, Ithaca, NY 14853. E-mail: jlw43@cornell.edu 726 WHITLOCK, MUEHLENKAMP, ECKENRODE studies with regard to correlates of NSSI. For example, although it is largely accepted that NSSI is a behavior with an origin in early adolescence, some studies have documented an age of onset in early to middle child- hood among some individuals (see Yates, 2004, for review). Similarly, a recent college population study found that almost 40% of self-injuring individuals report an average age of onset in late adolescence or early adulthood (Whitlock et al., 2006). Similarly, many studies report that female individuals are more likely to engage in NSSI than male (Laye-Gindhu & Schonert- Richl, 2005; Rodham, Hawton, & Evans, 2004; Whitlock et al., 2006), whereas others find that male individuals are equally likely to self-injure as female, particularly among nonclinical samples (Garrison, Addy, McKeown, & Cuffe, 1993; Gratz, 2001; Klonsky, Oltmanns, & Turkheimer, 2003; Muehlenkamp & Gutierrez, 2004). These variations may be accounted for by the type of behaviors studied, the sample popu- lation, or the frequency of the behavior. For example, in a sample of community adolescents, Muehlenkamp, Yates, and Alberts (2004) found that boys and girls dif- fered in the form of NSSI reported. Boys were more likely to engage in self-battery, whereas girls were more likely to report cutting and severe scratching. Similar results were reported by Whitlock et al. (2006) in their study of college students. The same study found that the frequency of NSSI varied by gender as well, with men and women equally likely to endorse a single act of NSSI, but women significantly more likely than men to report repeated acts of NSSI. Findings with regard to race and NSSI are also mixed, with some studies suggesting that it may be more common among Caucasians (Bhugra, Singh, Fellow- Smith, & Bayliss, 2002) and others showing similarly high rates in minority samples (Marshall & Yazdani, 1999; Whitlock et al., 2006). Although parallels between NSSI and eating disorders have led some to speculate that NSSI is likely to be most prevalent among middle- and upper-income individuals (Strong, 1999), no exist- ing research supports this contention. Indeed, other researchers have reported NSSI in low income popula- tions as well (Favazza & Conterio, 1989). Studies of NSSI characteristics in community popula- tions show considerable variation in the frequency and forms of NSSI behaviors reported as well. For example, reported lifetime NSSI frequency varies dramatically, from single incidents to hundreds of incidents (Laye- Gindhu & Sconert-Reichl, 2005). Similarly, although nonclinical samples often endorse a greater number of low-lethality NSSI forms than clinical samples (see Skegg, 2005), community studies show that individuals use a myriad of forms which vary dramatically in the capacity to cause tissue damage. Although cutting is one of the most common and well-documented NSSI forms, Whitlock et al. (2006) identified the presence of more than 16 forms in a college population. Moreover, several studies have shown that the number of forms used by an individual varies significantly, from 1 to over 10 (Laye-Gindhu & Schonert-Reichl, 2005; Whitlock et al., 2006). The lack of a coherent set of findings from prior NSSI studies could be the result of variation in NSSI definitions (Claes & Vandereycken, 2007; Linehan, 2000) but could also be because of the existence of dif- ferent subgroups or classes of self-injurers. There now appears to be broad agreement about what behaviors constitute NSSI (e.g., cutting, burning, self-hitting; Claes & Vandereycken, 2007; Walsh, 2006), but little is known about potential subgroups that might exist within this broad typology. Indeed, the heterogeneity of NSSI characteristics identified among self-injurers in both clinical and nonclinical settings led Walsh to propose a typology of NSSI for clinicians. Walsh pos- ited that most individuals engaging in NSSI can be classified into specific groups based on characteristics of the NSSI including the frequency of the behavior (episodic vs. repetitive), forms used (indirect; i.e., dam- age is accumulated over time such as with substance abuse vs. direct; i.e., cause immediate tissue damage such as with cutting), and extent of damaged caused by the act (common = low lethality vs. major = high lethal- ity). Walsh theorized that there may be important thera- peutic distinctions among these potential NSSI groups. Likewise, Joiner’s (2006) model of suicidal behavior assumes that there are important differences among individuals who vary in their frequency, form, and severity of NSSI and that these differences could help identify individuals at risk for suicide. Joiner theorized that NSSI and suicide may share common risk factors and that some suicidal individuals acquire the capacity to engage in high lethality behavior (i.e., suicide) by engaging in increasingly severe NSSI over time. He further proposes that individuals who attempt suicide are likely to have engaged in various forms of direct (e.g., cutting) or indirect (e.g., disordered eating) self- injury with increasing frequency and severity. This, in turn, fosters habituation to pain and fears of harm or death and ultimately enhances propensity for suicide. Although not widely tested, Joiner’s (2006) idea that NSSI may lead to increased vulnerability for suicide has received some empirical support. Studies have documen- ted that individuals who attempted suicide were more likely to have longer histories of, and use a greater num- ber of methods of, NSSI than those without a suicide attempt (Nock, Joiner, Gordon, Lloyd-Richardson, & Prinstein, 2006; Whitlock & Knox, 2007). It is also clear, however, that the majority of individuals who engage in NSSI do not exhibit any suicidality (Muehlenkamp & Guiterrez, 2004; Nock et al., 2006; Whitlock & Knox, 727 VARIATION IN NONSUICIDAL SELF-INJURY 2007). Thus, the conditions under which NSSI is linked to more lethal behaviors, such as suicide, are unclear but may vary as a function of NSSI characteristics. Considered together, the available data and theory suggest that there may be different types of self-injurious individuals in community populations that differ in terms of primary NSSI characteristics (e.g., frequency, form, function, age of onset) and demographic charac- teristics (gender, race, socioeconomic status [SES], and age of onset). It also suggests that although these classes may be conceptualized along a severity continuum based primarily on NSSI features, they may differ significantly in other ways as well such as in secondary NSSI charac- teristics (practices and routines) and psychosocial correlates, and treatment history. Based on these expec- tations, we hypothesized that (a) multiple NSSI typolo- gies can be identified based on primary NSSI characteristics that can be generally conceptualized along a continuum of least to most severe; (b) these typologies would have distinct differences in demo- graphic composition; and (c) the typologies would also show significant variation in secondary NSSI character- istics, psychosocial correlates, and help-seeking. the questions on this survey honestly’’) and systemati- cally looked for inconsistencies in responses within the self-injury data using three overlapping question sets designed to detect inconsistencies in responses. A total of 3,069 (36.9%) individuals completed the survey. Cases in which more than 90% of the responses were missing (n ¼ 115) or in which NSSI status was inde- terminable (n ¼ 77) were omitted, resulting in 2,877 (34.6%) retained for analysis. With the exception of the male-to-female respondent ratio (56.3% vs. 47.6%), the final sample was representative of the population from which it was drawn. Two thirds (66.7%) of the sample was Caucasian, 3.7% was non-Hispanic Black, 4.3% was Hispanic, and 17.4% Asian = Asian American. Ten percent were categorized as ‘‘other.’’ Father’s highest education level was used as an indicator of SES; 4.1% of the sample had fathers with less than a high school education, 7.2% completed high school, 10.7% had some college, 19.7% had completed college, and 58.4% possessed some postgraduate education. Partici- pant ages ranged from 18 to 43. For the purposes of these analyses, only those 24 and younger were included (n ¼ 2,101). Among these, 50.9% were younger than 20 and 49.1% were between the ages of 20 and 24. To assesses typologies of individuals for whom NSSI may have become habitual, analyses of self-injurious students were restricted to the 282 (13.4%) who reported two or more episodes of NSSI behavior. METHODS Participants Participants were drawn from a simple random sample of 8,300 undergraduate and graduate students from two northeastern universities. Invitees were selected by the university registrars using software designed to draw a true random sample from the student population. The only requirement was that the respondent be 18 years of age at the time the sample was drawn. The number of invitees was based on an anticipated 30% response rate, as this is typical of current survey research (Krosnick, Holbrook, & Pfent, 2003), and a 10% positive self- injury rate. All invitees were sent an advance postcard inviting them to participate in a Web-based ‘‘Survey of College Mental Health and Wellbeing,’’ in the spring of 2005. Soon after, each received a personalized e-mail with a link to the survey. By more obliquely advertising the purpose of the survey we aimed to reduce bias noted in similar studies of depression when the survey purpose is clearly stated (Hunt, Auriemma, Ashara, & Cashaw, 2003). We employed multiple response enhancement strategies (incentives, follow-up reminders, personalized invitations) and a Web-based survey format that allowed concealment of NSSI questions unless triggered by positive response to the NSSI screening question with the intention of reducing response bias as well. To assess respondent honesty, we asked respondents to indicate the degree of care, thoroughness, and honesty at the survey close using a Likert-type scale (e.g., ‘‘I answered Procedures The survey was administered on a secure Internet server and required 10 to 25min to complete. The Web-based survey allowed for complex skip patterns viewable only by those for whom the questions were relevant. The sur- vey also allowed participants to immediately make the screen go blank if they were interrupted. Links to local resources were placed on the bottom of every page, and a ‘‘distraction’’ toggle allowed anyone who needed a break to see an unrelated Web page. The study was approved by Committee for Human Subjects at both institutions. All participants provided online assent before taking the survey and were free to discontinue at any time by closing their Web browser. The survey included four broad conceptual domains: (a) sociode- mographic characteristics, (b) mental health indicators including a detailed section on NSSI, (c) risk and protec- tive factors, and (d) help-seeking and treatment history. Measures NSSI. To assess the presence of NSSI, all respon- dents received a screening question for self-injurious behavior: ‘‘Have you ever done any of the following with the intention of hurting yourself?’’ They were then presented with a list of 16 self-injurious behaviors 728 WHITLOCK, MUEHLENKAMP, ECKENRODE selected from existing NSSI surveys (Mann, Waternaux, Hass, & Malone, 1999), a review of existing literature, and interviews with mental health providers and self- injurers. They were also asked to estimate the lifetime number of NSSI incidents based on six possible responses: once, 2 to 5 times, 6 to 10 times, 11 to 20 times, 21 to 50 times, and more than 50 times. For the sake of parsimony in the Latent Class Analysis (LCA), lifetime NSSI frequency was collapsed into three cate- gories: 2 to 10 incidents, 11 to 50 incidents, and more than 50 incidents. To ensure that such reduction did not increase error, we first ran the analysis with all levels included. The expanded model did not change the results found of the more parsimonious three-level model and did add additional error. Because of this, we opted to use the three-level version of the NSSI fre- quency variable. A dummy variable was created to reflect the total number of different NSSI forms used: one, two to three, and more than three. Using a slightly modified version of the lethality continuum postulated by Skegg (2005), another dummy variable was created by collapsing the 16 NSSI forms into three discrete categories ordered by potential degree of tissue damage. The first group consisted of behaviors with the potential for superficial tissue damage (e.g., scratching or pinching to the point that bleeding occurs or marks remain on the skin; inten- tionally preventing wounds from healing). The second group included behaviors likely to cause bruising or light tissue damage such as punching or banging oneself or other objects (with the express intention of hurting the self), sticking sharp objects into the skin (not includ- ing tattooing, body piercing, or needles used for medica- tion use), and self-bruising. The last group comprised behaviors with the potential of severe tissue damage such as cutting or carving the body, burning areas of the body, breaking bones, dripping acid onto skin, and ingesting a caustic substance(s) or sharp object(s). Self-injurious respondents were also asked questions assessing (a) age of onset, (b) NSSI function, (c) current versus past NSSI, (d) addictive properties of NSSI, (e) perception that NSSI interfered with life, (f) unintended physical consequences, (g) routines and practices, and (h) treatment history. Age of onset was assessed with a single item that asked, ‘‘How old were you the first time you intentionally hurt yourself?’’ Nine response options were collapsed into three levels for the current analysis: childhood or early adolescence ( < 13), middle ado- lescence (13–16), or late adolescence ( > 16). NSSI func- tion was assessed through an item that asked respondents to select all options that best completed the statement ‘‘I intentionally hurt myself ....’’ Respon- dents were presented with 17 possible options (e.g., ‘‘to relieve stress or pressure’’ and ‘‘to shock or get back at someone’’) that were grouped into categories based on the four dimensions suggested by Nock and Prinstein (2004): social positive, social negative, automatic posi- tive, and automatic negative. Current versus past NSSI status was determined using an item that asked respondents to estimate the length of elapsed time since their last NSSI incident. They were presented with seven options (e.g., ‘‘less than 1 week ago’’ or ‘‘between 6 months and 1 year ago’’). Anyone indicating that it had been less than 1 year was categorized as having current NSSI status. NSSI addiction characteristics were assessed using a four-item Likert-type scale. The items were based on common features of addiction (Shadel, Shiffman, Niaura, Nichter, & Abrams, 2000) and include measures such as ‘‘I have had to intentionally hurt myself more deeply and = or in more places on my body over time to get the same effect’’ and ‘‘When I have the urge to inten- tionally hurt myself it is hard to control it.’’ All items loaded above .7 on a single confirmatory factor analysis, and Cronbach’s alpha was .78. Perceived life inter- ference was a binary coded variable based on responses to five items that assessed degree of perceived inter- ference with life. Respondents endorsing one or more of the life interference items (e.g., ‘‘The fact that I inten- tionally hurt myself interferes with relationships which are important to me’’ and ‘‘The fact that I intentionally hurt myself interferes with my ability to complete school work or work obligations’’) were coded as 1 and those endorsing the item ‘‘It does not interfere with my life in any way’’ were coded as 0. The unintended physical consequences variable was similarly coded based on an item that read, ‘‘Have you ever intentionally hurt your- self more severely than you expected?’’ The NSSI section of the survey also included a ser- ies of binary coded questions (yes = no) on NSSI prac- tices and routines, three of which are included here: ‘‘I have friends who self-injure’’; ‘‘I tend to go through periods in which I self-injure, then periods in which I do not’’; and ‘‘I have a regular routine I follow when I self-injure.’’ Respondents were also asked to respond to a series of formal and informal help-seeking items, such as ‘‘Have you ever gone to a therapist (e.g., psychologist, psychiatrist, social worker) to explore an issue you yourself were having (not including family or couples’ therapy)?’’ ‘‘To the best of your knowledge, have you ever been diagnosed with any of the following:’’ (followed by a list such as depression, post traumatic stress disorder, etc.), and ‘‘Have you ever been prescribed medication for a mental health problem you were having?’’ Individuals responding that they had been diagnosed with any of the Diagnostic and Statistical Manual of Mental Disorders (4th ed. [DSM–IV]; American Psychiatric Association, 1994) disorders listed were coded as hav- ing received a diagnosis. 729 VARIATION IN NONSUICIDAL SELF-INJURY Suicidality and trauma history. Lifetime suicidality was measured using a binary response item that asked, ‘‘Have you ever seriously considered suicide or attemp- ted suicide?’’ Individuals who answered affirmatively were asked to select any of eight statements that applied to them. For purposes of these analyses, these state- ments were clustered into the three following categories: ideation (e.g., ‘‘I thought seriously about it’’), plan or gesture (e.g., ‘‘I had a general plan but did not carry it out,’’ ‘‘I wrote a suicide note but did not leave it where it could be found’’), and attempt (e.g., ‘‘I made a serious attempt but no medical intervention occurred’’). Parti- cipants with multiple responses were placed into only one of these categories based on their most severe response selection. A binary variable reflecting the presence of four DSM–IV characteristics of disordered eating was coded positively if respondents indicated that they had ever repeatedly: severely restricted eating, binged or purged, overexercised to lose or manage weight, or used laxa- tives to lose or manage weight. Presence or absence of abuse history was measured using three questions developed for this study, ‘‘Have you ever been in a phy- sically abusive relationship (including family relation- ships, romantic relationships, acquaintances, or friendships)?’’ ‘‘Have you ever experienced genital touching or penetration against your will?’’ and ‘‘Have you ever been in a relationship that was emotionally abusive (including family relationships, romantic rela- tionships, acquaintances, or friendships)?’’ checking for model fit and significance until the model which best fit the data was determined. Model fit was determined by evaluation of the Consistent Akaike’s information criteria (Akaike, 1974), the Bayesian infor- mation criterion, which has a more stringent penalty for the number of extra parameters (Kass & Wasserman, 1995), and the entropy score. Lower Consistent Akaike’s information criteria and Bayesian information criterion values indicate improvement of the model rela- tive to the model with one less class. Higher entropy scores reflect better fit. We also evaluated the difference between the log-likelihood of the previous and the current class. LCA resulted in the creation of three distinct classes; thus, a single variable was created to represent these classes and was included as the dependent variable in multinomial logistic regression analyses. The inde- pendent variables included in the analyses include mea- sures of NSSI practices not included in the classification model, as well as psychosocial variables and treatment history. Both unadjusted and adjusted models including gender, race, age, and SES were conducted. To assess the extent of difference in each class with no NSSI, the final analysis used binary and multinomial logistic analyses to compare respondents who reported no NSSI with each of the classes. Because population parameters for key demographic characteristics were known, all analyses were weighted to control for gender differences between the sample and the population and to equalize differences in response rates in each university. Statistical Analyses RESULTS The first set of analyses used LCA to identify subpopu- lations of NSSI membership using several features of NSSI behavior. LCA can be best understood as a categ- orical analogue of factor analysis and is particularly appropriate for data with a limited number of levels. An LCA solution is most optimal when classes are as homogenous as possible and differences between classes are as large as possible (Hagenaars & McCutcheon, 2002). Various forms of the unobserved latent class variable were fitted to the data using Latent GOLD, version 4.0 (Statistical Innovations, Inc., 2005). Conven- tional goodness-of-fit statistics were used in the model choice process, and bivariate residuals were examined to ensure that the assumption of local independence between observed variables was not violated (Magidson & Vermunt, 2000). The first model used lifetime number of NSSI inci- dents, number of NSSI forms used, potential degree of tissue damage inflicted, age of onset, and function. Cov- ariates included in the first LCA model included: gen- der, race, age, and SES. We first computed only a single latent class and added one class after another Class Descriptions Iterative comparisons of fit for a one- to four-cluster solution using variables added stepwise showed best fit when only lifetime number of NSSI incidents, number of NSSI forms used, and potential degree of tissue dam- age inflicted were used. Neither age of onset nor function contributed significantly to the model. Examination of the LCA results using reported lifetime NSSI prevalence, number of forms used, and degree of tissue damage inflicted showed a three-class solution to best fit. Gender was the only covariate to remain in the final model. Examination of bivariate residuals showed all less than two except those between gender and NSSI form, so gen- der was entered as a direct effect in the final model. Latent Gold allows categorical independent variables to be entered as nominal or ordinal. Examination of a one- to four-class solution with all nominal versus ordinal permutations of the independent variable showed that a three-class solution with all variables entered as ordinal and gender entered as nominal had the lowest Consistent [ Pobierz całość w formacie PDF ] |