Epidemiology of Non-Suicidal Self-Injury in Adolescence
Non-suicidal self-injury (NSSI) comprises deliberate and conscious acts without intention to die. These behaviors can cause immediate physical damage on the own body tissue including for example cutting, scratching, biting, burning, hitting oneself (International Society for the Study of Self-Injury 2018). These socially unacceptable behaviors are the most common during adolescence (Brown & Plener 2017). According to different surveys, lifetime prevalence of NSSI ranges between 13% and 38% in community adolescent samples (e.g., Brunner et al. 2014; Jacobson & Gould 2007). A systematic review of more than 50 studies concluded that the mean lifetime prevalence of NSSI behaviors was 18% during adolescence (Muehlenkamp, Claes, Havertape, & Plener 2012). However, this review drew attention to that there is a substantial difference in the estimates of lifetime prevalence of self-harm depending on the way of assessment. While single binary item assessment showed a 12.5% average lifetime prevalence, multiple items or behavior checklist method indicated almost twice (23.6%) lifetime prevalence (Muehlenkamp et al. 2012).
Frequency of self-harm is also an important consideration. Although, in adolescent samples, 17-18% international lifetime prevalence were reported for at least one NSSI episode (Swannell, Martin, Page, Hasking, & John, 2014), significantly fewer young people who engage in self-harm satisfy the cumulative criteria of the non-suicidal self-injury disorder (NSSID) which can be found in the recent edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5; American Psychiatric Association, 2013) as a condition for further study. According to the review of Zetterqvist (2015), prevalence of repetitive self-harm in the past year (as defined NSSID) ranged between 1.5 and 6.7% in child and adolescent non-clinical samples.
Furthermore, the Child & Adolescent Self-Harm in Europe (CASE) Study pointed out that nearly 15% of the mainly 15-16 year old adolescents reported self-harm thoughts in the past year, but only 5.8% engaged in self-harm (2.6% engaged in single self-harm episode, while 3.2% engaged in it multiple times) (Madge et al. 2011).
Research have consistently shown that adolescent girls are at greater risk of NSSI than boys, especially in clinical populations (Bresin & Schoenleber, 2015). There is also a gender difference in the most common method of self-harm. While girls mainly engage in self-cutting and carving their skin, boys hit themselves the most likely in a community adolescent sample (Barrocas, Hankin, Young, & Abela, 2012). An other important confounding factor would be intercultural differences in self-harm prevalence (Brunner et al. 2014) and behaviors (Madge et al. 2008).
Moreover, using multiple forms of NSSI are more likely to be linked to more severe intrapersonal and interpersonal problems (Zetterqvist, Lundh, Dahlström, & Svedin 2013), and probably to more dysfunctional emotion regulation.
Motivation for engaging in self-harm
The Four Function Model (FFM; Nock & Prinstein 2004) is one of the most cited functionality model of NSSI. According to the FFM-theory, NSSI acts can serve as intrapersonal (“automatic”) together with interpersonal (“social”) mechanisms and both processes can reinforce the behavior positively or negatively. In this model, self-harm can (1) decrease negative emotional experiences (automatic negative reinforcement) or (2) generate a (desirable positive) emotional state (automatic positive reinforcement) and can (3) reduce (social negative reinforcement) or (4) induce specific interpersonal experiences (social positive reinforcement). Automatic (intrapersonal) funtions are much more common than the social (interpersonal) functions (Brackman & Andover, 2017). In a review, Klonsky (2007) also affirmed that affect-regulation function is the leading motive of engaging in NSSI. Self-punishment was also a common reason for NSSI, but there was less evidence of anti-dissociation, anti-suicide, sensation-seeking, as well as interpersonal-influence and interpersonal boundaries functions of NSSI (Klonsky, 2007).
These results were also confirmed in a meta-analysis, which included 53 independent samples (Taylor, Jomar, Dhingra, Forrester, & Shahmalak 2018). Intrapersonal functions of self-harm were more prevalent (66-81% of participants) than interpersonal motives (32-56% of participants). In particular, the aim of avoide or escape from an unwanted internal state was the most common intrapersonal function, while self-punishment and inducing positive feelings via self-harm were the less frequent ones (on average 50% of the participants). Communicating distress was the most frequent interpersonal function, whilst punishing or hurting others was the least frequent (Taylor et al. 2018). However, a systematic review pointed out that social contagion (i.e., influence of the (social) media and friends) has a great impact on the first engagement in NSSI. On the contrary, repeated NSSI mainly influenced by intrapersonal functions (Jarvi, Jackson, Swenson, & Crawford, 2013).
Similarly to some sociodemographic differences in self-harm prevalence and methods, it would be appropriate to examine whether the main motives underyling the self-harm act does not depend on certain characteristics of the participants, such as age, gender, socioeconomic status, clinical or community samples, or even (sub)cultural background. Only a limited number of studies tested the role of gender in self-harm functions. Gender differences were detected in the background of deliberate self-cutting: female adolescents stated twice as high than boys they cut themselves because of they wanted to punish themselves. Similar gender pattern showed in the reason of reducing an unwanted state of mind (Rodham, Hawton, & Evans 2004). However, in a study, which involved 7 countries, were not presented gender and cultural differences in self-harm motives. Researchers only could justify that girls reported more reasons behind self-harm than boys. Furthermore, adolescent girls showed difference according to age: older girls more frequently used self-harm as a cry for help act (Scoliers et al. 2009).
Analysis of NSSI-functions based on the Inventory of Statements About Self-Injury
The second part of the Inventory of Statements About Self-Injury (ISAS Part II; Klonsky & Glenn 2009) measurement has been developed to be capable of assess the underlying causes of NSSI. Already in the initial study, the assessed 13 empirically substantiated motives can be classified into two broader, intrapersonal and interpersonal, functions with exploratory factor analysis (EFA). These two robust factors harmonized with the concept of Nock and Prinstein’s (2004) FFM model. The intrapersonal factor comprised 5 subscales: affect-regulation, anti-dissociation, anti-suicide, marking distress, and self-punishment functions of NSSI. While, the interpersonal factor concentrated 8 subscales. Autonomy, interpersonal boundaries, interpersonal influence, peer-bonding, revenge, self-care, sensation seeking, and demonstrating toughness built up the social aspects of NSSI functionality. Only in one of the 13 functionality scales emerged some uncertainty: factor loadings of self-care were marginally different in the case of the interpersonal (.41) and intrapersonal (.33) factors. Furthermore, self-care (when someone engages in self-harm to create a physical wound to care about, instead of experiencing emotional distress) would be a better fit for the intrapersonal factor, conceptually.
The two-factor structure was not affected by gender and ethnicity (Klonsky & Glenn, 2009). Moreover, the two larger factors showed excellent internal consistency and the required associations with clinical phenomena like mood and borderline personality disorder symptoms, as well as suicidality (Klonsky & Glenn 2009). Due to the good reliability and validity of the questionnaire, the ISAS has quickly spread in self-harm studies.
All of the further studies could strenghten the two-factor framework of the ISAS Part II. In 2015, Klonsky and his colleagues affirmed with EFA the intra-, and interpersonal factors in a large clinical sample with a wide age range (from 11 to 73 years old). In keeping with the above, in this analysis, one item (item 17) of the self-care subscale loaded on the intrapersonal factor, while the other two (item 4 and 30) connected clearly to the interpersonal factor (Klonksy, Glenn, Styer, Olino, & Washburn 2015).
Among others, in English-speaking countries (e.g., UK, USA, Canada, Australia) Kortge, Meade and Tennant (2013) also supported the intra-, and interpersonal function factor structure of the ISAS with EFA. Participants over 18 years who joined in online deliberate self-harm peer support groups filled out, inter alia, the ISAS. In this research, the self-care subscale clearly loaded into the intrapersonal factor. In this way, the intrapersonal factor comprised 6 subscales (affect-regulation, anti-dissociation, anti-suicide, marking distress, self-punishment, and self-care), while the interpersonal factor brought together 7 subscales (autonomy, interpersonal boundaries, interpersonal influence, peer-bonding, revenge, sensation seeking, and toughness). Based on Rasch analysis, Kortge and her colleagues demonstrated that the most relevant functions for the respondents were interpersonal boundaries and toughness, however, peer bonding was the least relevant in the case of the interpersonal factor. As regards the intrapersonal factor, the strongest endorsed functions were affect-regulation and self-punishment, while the weakest was the motive of self-care. Item functioning was independent from age, nationality, and education level (Kortge et al. 2013).
Similarly, in Turkish (Bildik, Somer, Kabukcu Basay, Basay, & Ozbaran 2013), Korean (Kim, Kim, & Hur 2019), and Spanish (Pérez, García-Alandete, Cañabate, & Marco 2020) samples, the ISAS Part II presented a definitely two-factor structure. Among Turkish high school students Bildik and her colleagues supported the two-dimension model (self-care scale was considered as an interpersonal function) with confirmatory factor analysis (CFA) (Bildik et al. 2013). However, the correlation was particularly high between the implicit factors, suggesting the legitimacy of a general function factor with specific self-harm motives. A recent CFA-analysis on a Spanish clinical sample could confirm the two-factor structure model, where self-care loaded into the intrapersonal factor (Pérez et al. 2020). As a result of the relatively low subsample size of patients with borderline personality disorder, authors could not test invariance according to diagnosis (Pérez et al. 2020). It must be stressed that none of the above mentioned studies analyzed gender or age invariance in the factor structure of the ISAS Part II.
Current study
Based on the review of previous studies on the ISAS, our first aim was to validate the questionnaire and provide NSSI demographics in a Hungarian adolescent sample. On the other hand, we aimed to analyze the factor structure of the ISAS functions (ISAS Part II short version). In this context, our purpose was to further discuss the dimensionality of the ISAS functions in a confirmatory factor analysis (CFA) and exploratory structural equation modeling (ESEM) framework. Beyond the traditional CFA, ESEM analysis can provide a more realistic test of the theoretical constructs and also more accurate estimation of factor intercorrelations. In addition, due to the lack of testing measurement invariance of the ISAS functions (ISAS Part II) in the previous research, we examined measurement invariance across gender and analyzed gender differences in the factor structure. A further objective of our study was to explore the associations between the functionality factors being found and relevant variables, such as mental health symptoms, emotion regulation aspects, as well as certain features of the self-harm behavior (methods and attitudes related to the self-harm act).