In light of the reciprocal relationship between suicidal ideation and NSSI, recent studies have examined suicidal ideation as a risk factor for involvement in NSSI behaviors [30]. Indeed, although several studies have investigated the pathway leading from self-injury to the development of suicidal ideation [31,32] the pathway from suicidal ideation to NSSI behaviors has been less investigated.

A recent study by Herzog et al. [33] explored the use of NSSI to curb thoughts referred to suicidal behaviors. Preliminary results show how, in addition to regulating dysphoric emotional states, NSSI can be enacted to regulate distress arising from suicidal thoughts. One possible explanation for this process could refer to the immediate goal of temporarily relieving distress, as a trade-off for the permanent solution that suicide represents [34]. Understanding what mechanisms might explain this relationship assumes theoretical and clinical relevance in order to provide insights into the risk factors for the development of NSSI behaviors, the dynamics underlying the reasons for self-injurious behaviors, and to contribute to the implementation of accurate and targeted interventions.

The model of emotion dysregulation [15] conceptualizes alterations in the ability to regulate emotions across six dimensions: low levels of emotional awareness, poor clarity of emotions, poor ability to maintain goal-oriented behavior when experiencing intense and negative emotions, poor control under the influence of negative emotional states, poor perceived ability to access various emotional regulation strategies, and a tendency to negatively judge internal emotional states.

A substantial body of research has supported the involvement of emotional dysregulation in various dysfunctional behaviors and psychopathologies [11,35,36] such as, for example, in the mechanisms of suicidal ideation and NSSI.

Studies show a reciprocal relationship between emotional dysregulation and suicidal ideation, in fact, if a poor ability to regulate emotions can lead to thoughts that refer to suicide as strategies to alleviate emotional suffering, self-perception of a poor ability to regulate emotions, and ruminating thoughts about death also have a significant influence on the self-efficacy of regulation skills [37]. A recent systematic review [38] showed the presence of positively correlated associations between emotion dysregulation and suicidal ideation, particularly with regard to suicidal ruminations versus bodily experience [39]. In addition, the predictive value of emotion dysregulation with respect to the development of suicidal ideation and future suicidal intentions has been reported [40]. In general, studies recommend that difficulties in emotion regulation have an important function in suicidality, especially in individuals with pathological personality or other psychiatric comorbidities [41].

In line with this perspective, theoretical models that conceptualize suicidal phenomena and NSSI behaviors as functions of avoidance or escape from an emotional state intolerable to the subject [42] emphasize the role of emotion dysregulation in the origin of the development of ideas and behaviors of self-directed violence.

Similarly, the literature on suicidal antecedents, and particularly on NSSI, conceptualizes this behavior as a maladaptive response to strong emotional states with negative valence [43]. Indeed, the results of the study conducted by Houben et al. [44] on the qualitative aspect of NSSI-related emotions provided relevant evidence on the clinical aspect of NSSI and stimulated reflections on the role of positive emotions. They showed that the likelihood of enacting NSSI behaviors is predicted by a high intensity of negative emotions and that, upon the occurrence of the self-injurious behavior and in the subsequent time interval, there is an increase in negative emotions, rather than emotional relief. Thus, if positive emotions are not the result of self-injurious regulatory behavior, they could also be studied. In fact, a recent systematic review of the literature on the topic has emphasized the conceptualization of NSSI as a maladaptive behavior to strong negative affect, and theoretical and empirical work has suggested that it has a coping function for emotional intensity resulting from poor regulation skills [43]. Most contemporary models of NSSI recognize the contribution of emotional dysregulation in the development and maintenance of NSSI; in particular, the experiential avoidance model of self-injury [34] suggests that NSSI has an avoidance function from unwanted emotional arousal that is exacerbated by deficits in emotional regulation skills and poor distress tolerance as triggers of NSSI behavior.

Based on the interesting findings on the central function of emotional dysregulation in the development of NSSI behaviors and suicidal ideation, the current study aims to further clarify the association between suicidal ideation, NSSI, and emotional dysregulation, and to fill a theoretical and empirical gap by including positive emotional regulation skills in the framework.

In fact, although the involvement of negative emotion dysregulation has been extensively studied, especially in clinical populations and in relation to suicide risk [45,46], there is a paucity of findings related to the role of positive emotion dysregulation in nonclinical populations. Research on positive emotion regulation difficulties is an area of considerable scientific interest that has grown in recent years, particularly in the study of various psychopathological forms [47]. Surprisingly, only a few studies have examined the link between positive emotion regulation, NSSI, and suicidal ideation. Therefore, it seems necessary to fill this gap and understand whether positive emotion regulation difficulty is involved in self-directed violence behaviors and ideas, and to study the link between NSSI and suicidal ideation in relation to difficulties in regulating emotional states in community samples, in order to understand how to intervene. The overall goal is to explore the type of link between suicidal ideation and NSSI behaviors in a nonclinical population through understanding the role played by dysregulation of positive and negative emotions. Specifically, based on recent findings demonstrating the function of NSSI as a regulation behavior for distress elicited by suicidal thoughts [33], we hypothesize that this relationship is mediated by the dimensions of emotional dysregulation based on the link that emotional dysregulation shows with the development of suicidal ideation and self-injurious behavior. Therefore, we hypothesize that individuals with emotional dysregulation are unable to cope with suicidal thoughts and seek to regulate the negative emotions aroused through NSSI. The aim is to contribute to the expansion of knowledge on the origin of self-directed violence behaviors by studying the role of emotional dysregulation in the relationship between suicidal ideation and NSSI.

For the purposes of the study, a group of community participants was recruited through a convenience sampling technique. For participation in the study, subjects who were 18 years of age or older, literate and had provided informed consent for voluntary participation in the project were included. Excluded from the study were those under the age of 18 years, those who were non-literate, those with disabling physical impairments, those with psychopathologies, and those who had not provided informed consent for participation. Before completing the questionnaires, the purposes of the research and the information on privacy and anonymity were explained to the participants who were requested to sign an informed consent to participate in the research. The sample on which the analyses were conducted included a total of 1,202 participants (34.3% male), with an average age of 30.48 (standard deviation=13.32) years.

The research procedures were in conformity with the official guidelines of the American Psychological Association and were also approved by the Ethics Board of the Sapienza University of Rome (No. 21/2018).

This study is measured a battery of self-assessment questionnaires through which several domains were surveyed. Demographic information and clinical history were asked in an initial questionnaire created ad hoc for the purpose of the study.

Suicidal ideation was assessed using Beck Suicide Ideation Scale (BSI) [48], a self-assessment tool that assess the intensity of suicide behaviors, attitudes, and plans. This scale is composed of 21-items. The first 19 ones have three options that evaluate the intensity of suicide ideation on a 3-point scale ranging from 0 to 2. Then, the ratings are totaled to obtain a total point score ranging from 0 to 38. The latter two items assess the previous number of suicide attempts and the severity of the intent to die referred to the last attempt. In our study, Cronbach’s alpha for the sum of the total score 0.80.

NSSI was assessed trough Deliberate Self-Harm Inventory (DSHI) [49,50], a self-report composed by 17 items. Each item entails 5 supplementary questions that explore different features of self-injury behavior, such as severity, frequency, form, and duration, and which examines retrospectively the development of that specific behavior. The information obtained from DSHI provide two variables: one continuous and one dichotomous. The first, which derived from the sum of the score of each item’s frequency questions, measures the rate of reported self-harm behavior. The second, dichotomous variable, involves that is assigning score of “1” if participant answered “yes” to any of the 17 items; otherwise, if participant did not answer “yes” to any items of DSHI, he receives score of “0.” In our study, Cronbach’s alpha was 0.88.

Difficulties in the regulation of negative emotions were assessed using the Difficulties in Emotion Regulation Scale (DERS) [15,51]. This instrument is a self-report questionnaire that measures overall emotion dysregulation, obtained from the sum of six subscales that assess different regulation features namely: 1) impulse-control difficulties; 2) difficulties engaging in goal-directed behavior; 3) lack of emotional awareness; 4) lack of emotional clarity; 5) limited access to effective emotion-regulation strategies; and 6) non acceptance of emotional responses. Participants are equested to mark how frequently the items apply to themselves, with Likert-type scale answers from 1 (“never”) to 5 (“always”). In our study, all Cronbach’s alphas were satisfying, ranging from 0.81 (clarity) to 0.94 (DERS total score).

Difficulties in the regulation of positive emotions were assessed trough Difficulties in Emotion Regulation Scale-Positive (DERS-P) [47,52]. This scale is a 15-item self-report questionnaire shaped on the original DERS [15] to evaluate difficulties arising from experiencing positive, rather than negative emotions DERS-P examines three domains of emotion regulation, namely: 1) acceptance of positive emotions; 2) ability to engage in goal-directed behavior when experiencing positive emotions; and 3) ability to control impulsive behaviors when experiencing positive emotions. Participants are asked to indicate how often the items apply to themselves, with Likert-type scale responses ranging from 1 (“never”) to 5 (“always”). Raised scores indicate a higher difficulty in the regulation of positive emotions. In this study, Cronbach’s alphas ranged from 0.80 (acceptance of positive emotions) to 0.88 (DERS-P total), indicating a good reliability.

For the analyses conducted in the current study, we used IBM SPSS version 27.0 (IBM Corp., Armonk, NY, USA) software and PROCESS macro created fot the sotfware. Descriptive statistics were performed including mean and standard deviation calculation and computation of frequencies. Correlation analyses were then performed (Pearson’s r) followed by hierarchical multiple linear regressions used to test our mediation hypothesis.

To explore the relationships between suicidal ideation, NSSI, and emotion dysregulation, partial correlations, controlling for age and gender, have been performed and are displayed in Table 1. Overall, it resulted that DSHI scores were highly correlated both with BSI scores (r=0.43; p<0.001) and with difficulties to regulate positive and negative emotional status with coefficients ranging from 0.30 (DERS total scores) to 0.11 (goals).

Concerning suicide ideation, we obtained similar results: it significantly and positively correlated with both DERS and DERS-P total scores and subscales, with coefficients ranging from 0.33 (DERS total scores) to 0.14 (awareness).

With the aim of exploring which dimensions would predict NSSI, we ran a hierarchical multiple linear regression entering age and gender in the first step, total index of BSI in the second one, total index of DERS in the third model, and DERS-P in the final one. As displayed in Table 2, we found that both BSI and DERS predicted DSHI scores, whereas DERS-P was a non-significant predictor of NSSI.

In order to explain the trajectory by which suicide ideation leads to NSSI behavior, we tested the mediating role of emotion dysregulation. As showed in Table 3, we first ensured that suicide ideation predicted NSSI (Phase 1), that suicide ideation predicted difficulties in emotion regulation (Phase 2), that emotion dysregulation was a meaningful predictor of NSSI beyond the role of suicide ideation (Phase 3). Finally, in the fourth step, we examined the hypothesis that the link between suicide ideation and NSSI would have been mediated by emotion dysregulation. Results indicated that the pathways by which suicide ideation leads to NSSI is partially mediated by levels of emotion dysregulation (Figure 1).

Although rigorously conducted, this work is not without its limitations. In fact, our study was conducted on a sample composed of individuals from the general population, although rather large this does not provide an opportunity to generalize the results to clinical samples that might show different and peculiar characteristics that should be further investigated with subsequent studies. Also, the descriptive analyses dwelt on the study of gender and age. Later studies could also analyze other sample characteristics such as socioeconomic status and educational level. Moreover, another limitation concerns the lack of measurement of potential confounding variables, such as depressive and anxiety symptomatology. In fact, our study aimed to specifically assess the trajectory from suicidal ideations to non-suicidal acts of self-harm, attending to the mediating role of emotional dysregulation. Further studies could explore this pathway in populations with significant levels of anxiety or depression.

In addition, self-injurious behaviors were measured with a dichotomous instrument, not allowing in-depth investigation related to the motivations behind NSSI.

Future research could explore the motivational aspect related to NSSI to better understand the relationship with both dysregulation of negative and positive emotion. Finally, in order to test such a large sample, self-report instruments were used in this research, which, as is widely known in the literature, may exhibit bias related to social desirability.

In conclusion, although NSSI is traditionally distinguished from suicidal intent because of the absence of the aspect related to the desire to die, it might be interesting to explore the intentional aspect in patients who present with persistent and severe self-injurious behaviors. In addition, it might be useful to replicate our results by also studying other mechanisms related to the construct of emotional dysregulation (e.g., alexithymia, dissociation) that can influence the link of suicidal ideation and NSSI.