Definition, onset and course of NSSI

The rationale for categorising NSSI as a disorder remains in flux, with a paucity of data on adolescence. In this special issue, Brager-Larsen et al provide justification for the categorical distinction and early screening for NSSI disorder (NSSID). ^{Reference Brager-Larsen, Zeiner and Mehlum6,Reference Jarvers, Heidingsfelder, Ecker, Kandsperger, Brunner and Schleicher7} In their study of out-patient adolescents with recurrent self-harm, about half met DSM-5 criteria for NSSID. Compared with those not meeting the criteria, the NSSID group showed worse global functioning; greater frequency of both NSSI and suicide attempts; more severe depressive and anxiety symptoms; and a larger number of self-harm methods. ^{Reference Brager-Larsen, Zeiner and Mehlum6,Reference Jarvers, Heidingsfelder, Ecker, Kandsperger, Brunner and Schleicher7} These results provide a framework for directing future efforts investigating the clinical utility of the NSSID diagnosis in adolescents. Meanwhile, because much of the research focuses on NSSI as a transdiagnostic behaviour outside of the context of its own specific disorder, in this Editorial we focus primarily on the more broadly defined behaviour of NSSI.

Although the emergence of NSSI behaviour prior to adulthood is well established, an important question for the field has been the extent to which NSSI continues past the adolescent period. To address this, three papers in this special issue (all from the same research group) examined factors related to persistence in young adulthood. First, Jarvers and colleagues examined relationships among early traumatic experiences, depression and emotion regulation in university students with a lifetime NSSI history. ^{Reference Jarvers, Heidingsfelder, Ecker, Kandsperger, Brunner and Schleicher7,Reference von Perponcher, Jarvers, Ecker, Heidingsfelder, Kandsperger and Brunner8} A history of emotional abuse during childhood or adolescence predicted emotional reactivity, aggression and depression, but not persistent NSSI. Rather, persistence of NSSI beyond adolescence was predicted only by the use of NSSI for automatic positive reinforcement. ^{Reference Jarvers, Heidingsfelder, Ecker, Kandsperger, Brunner and Schleicher7,Reference von Perponcher, Jarvers, Ecker, Heidingsfelder, Kandsperger and Brunner8} Second, Schleicher and colleagues examined the impact of the COVID-19 pandemic on the persistence of NSSI in university students. They found that, compared with those who had desisted NSSI, individuals with persistent NSSI showed significantly greater urges to self-injure and significantly higher depression scores during versus pre-pandemic. ^{Reference Schleicher, Heidingsfelder, Kandsperger, Jarvers, Ecker and Brunner4,Reference Mars, Heron, Klonsky, Moran, O’Connor and Tilling5} Third, von Perponcher and colleagues employed a mixed-methods analysis to characterise the dynamics of NSSI history during childhood and adolescence in 185 university students. Data were compiled from three questionnaires detailing depression, reasons for self-injury, coping mechanisms and stress factors. Results indicated that NSSI continuation into adulthood was more likely to occur in the context of ongoing experiences of violence and trauma. ^{Reference von Perponcher, Jarvers, Ecker, Heidingsfelder, Kandsperger and Brunner8} Together, this body of work advances our knowledge of the key factors contributing to the persistence of NSSI, and can serve to guide intervention strategies to address the sequelae of emotional abuse, address emotional reactivity and aggression and help young people find more adaptive strategies to regulate their emotions and behaviour.

Biopsychosocial formulation

The papers in this thematic series are intended to serve as a framework to support a biopsychosocial formulation to understanding and treatment-planning for adolescents and emerging adults presenting with NSSI. Comprehensive case formulations are critical to aid in treatment selection and response-monitoring efforts. Against a backdrop of long-standing paucity of information about the neurobiological factors underlying NSSI, three papers in this special issue add new knowledge in this area. Psychological factors explored include stress, thinking styles, emotion-regulation styles and emotion understanding (alexithymia.) Social factors such as victimisation and ongoing trauma are also highlighted in this issue, demonstrating risk for symptom maintenance.

Biological factors

In a longitudinal study published in this issue, Bai et al examined pro-inflammatory cytokines in adolescents with a history of NSSI and suicidal behaviours. Higher levels of interleukin 6 were associated with greater frequency of NSSI over the ensuing 3 months in this sample. This is a promising result, because it suggests a biological marker of short-term risk for NSSI that, if replicated, could have strong potential for feasible translation into clinical practice. ^{Reference Bai, Asarnow, Babeva and Irwin9}

Applying an experimental probe to better understand brain functioning in adolescent NSSI, Höper et al used functional near-infrared spectroscopy to examine prefrontal oxygenation in the context of a social stress paradigm in adolescent NSSI, and a severity spectrum of borderline personality disorder (BPD) symptoms compared with healthy controls. ^{Reference Höper, Kröller, Heinze, Bardtke, Kaess and Koenig10} They found greater prefrontal cortex (PFC) activation in those with NSSI versus controls at baseline, and that higher activation in response to the stressor was associated with greater BPD symptoms. ^{Reference Papke, Klimes-Dougan, Sahasrabudhe, Mueller, Park and Öz11} This offers a potential tool to screen for, monitor and improve stress regulation with tailored therapeutic interventions in youth presenting with NSSI together with BPD symptoms. Furthermore, these results position PFC activation during stress as a candidate treatment target for future clinical experimental therapeutics trials.

One paper in the thematic series directly tested the biological effects of an intervention. ^{Reference Papke, Klimes-Dougan, Sahasrabudhe, Mueller, Park and Öz11} It followed up on an earlier, open-label pilot study that showed promise for N-acetylcysteine (NAC) to reduce NSSI in young people. Papke et al conducted a randomised, placebo-controlled clinical trial investigating glutathione and glutamate as potential biological signatures of NAC in treating young adults with NSSI. Although the trial results did not show the expected group differences regarding changes in biological signatures, the investigators reported that, across the sample, an increase in blood glutathione correlated with a decrease over time in suicidal ideation, ^{Reference Babaeifard, Mohammadkhani, Hasani, Shahbazian and Selby12} suggesting a potential target for testing of other agents in future experimental therapeutics clinical trials.

Overall, these papers suggest the importance of further research examining neurobiology in NSSI and its treatment. This kind of new knowledge is critically needed to inform and guide the development of novel interventions.

Psychological and social factors

Thematic series articles likewise identify psychological factors in the onset and maintenance of NSSI, including stress, emotion regulation and thinking patterns, and how social factors can shape the risk for NSSI. First, an elegant serial mediation analysis by Babeifard et al reveals rumination and experiential avoidance as mediating links between early maladaptive schema, NSSI and its functions. ^{Reference Babaeifard, Mohammadkhani, Hasani, Shahbazian and Selby12} These data provide new insights into how thinking styles can increase risk for NSSI in the context of specific experiences that occur over the course of development.

Second, gender-minority adolescents are over-represented among youth who engage in NSSI. ^{Reference Taliaferro and Muehlenkamp13} This disparity is thought to stem from the stigma and marginalisation that these youth have to face. White et al analysed data from a nationally representative birth cohort study in the UK. Gender-minority youth reported more emotional and behavioural difficulties, NSSI, psychological distress and suicide attempts than their cisgender peers; greater rates of victimisation were the inferred cause. ^{Reference White, Trinh and Reynolds14}

Third, in a Chinese sample of adolescents, both alexithymia (difficulty identifying feelings) and peer victimisation predicted meeting DSM-5 criteria for NSSID; peer victimisation also mediated the link between alexithymia and NSSI. ^{Reference White, Trinh and Reynolds14} The authors reflect on their findings against the backdrop of society in China that values maintaining harmony and collective over individual well-being, which could inform the capacity for identifying feelings. Their findings illustrate how social factors can shape risk pathways towards NSSI in culturally specific ways. ^{Reference Ruan, Liu, Shen, Wu and Yan15}

Treatment-seeking and barriers

Using a qualitative approach, Tickell and colleagues examined perceived facilitators and barriers in university students’ journeys to secure formal and informal support for their NSSI behaviour. ^{Reference Tickell, Fonagy, Hajdú, Obradović and Pilling16} Through serial interviews, their paper charts the course of 12 help-seeking students with NSSI and identifies 4 themes. First, the initial university phase was described as the most difficult for students, who were balancing transition into adulthood with student life demands while also working to establish new formal and informal support systems. The second theme captured which mental health problems were perceived as ‘valid’. This experience involves the frequently perceived invalidation by providers lacking the expertise to understand NSSI and/or assist students in managing their emotional turmoil. The third theme captured students’ pattern of evading external judgements, concerns and consequences via selective sharing of NSSI behaviours, with the goal of maintaining autonomy and reducing the impact of expected stigma. The final theme captured the pivotal role of treatment options and flexibility for recovery. A flexible structure prioritising student preferences and needs to direct mental health decisions and treatment, considered by students as vital, ^{Reference Tickell, Fonagy, Hajdú, Obradović and Pilling16} is perhaps the most difficult to achieve. ^{Reference Hawton17}

Clinical implications and future directions for research on prevention and treatment

There remains a dire need for advances in the treatment of NSSI in youth. ^{Reference Hawton17} Although research in this area is still at an early stage, consisting of preliminary findings requiring replication, the results reported in this special issue provide important new insights. Overall, the thematic series supports the critical importance of early identification and early interventions to mitigate both acute and long-term adverse outcomes. At a practical level, clinicians can use these new data by focusing on risk factors such as emotional abuse, victimisation related to gender identity, alexithymia and symptoms of BPD to identify patients who may need extra care in evaluation and intervention. From an advocacy perspective, data support the development of anti-bullying initiatives and policies to protect and safeguard the rights of transgender youth. From a research perspective, the data reported in this issue provide guidance for intervention development (e.g. experimental therapeutics clinical trials utilising biological targets such as interleukin 6, prefrontal oxygenation during stress and/or glutathione) and prevention development (e.g. tailored emotional literacy programmes) in emotion regulation. Overall, this body of work represents steps on the pathway towards enhancing our abilities to understand and support young people who engage in NSSI.