The findings of this study show that suicide ideation in adolescents with a history of NSSI and suicidal attempts are significantly more common than in adolescents with NSSI alone. This finding is consistent with prior studies that compare suicidal attempt indicators in adolescents (
6,
23). Unlike our results, which showed there was no significant difference between groups in terms of hostility-impulsivity and hopelessness, another research on adolescents from a psychiatric inpatient unit in the United States revealed that adolescents with NSSI and suicidal attempt were more hopeless and have higher scores in impulsivity (
24). This can be attributed to the setting of the studies and different scales used for assessing suicide probability indices. With this in mind, it can be concluded that the most reliable indicator of suicide probability is the experience of suicidal ideation. The findings of studies in adults in inpatient settings have revealed that suicidal thoughts remain relatively stable even after patients are released from the hospital (
25), so clinicians who work with adolescents who have a history of suicidal attempts should consider the risk of suicide and apply preventive programs to educate these adolescents in ways of coping with suicide ideation. It should be noted that, based on the results of the present study, adolescents with a history of suicidal attempts had the highest score in all of the suicidal probability subscales, but this difference was not significant. Suicide probability of adolescents with suicidal attempts and NSSI was greater than in the NSSI-only group, but the suicide probability of adolescents with both suicidal attempts and NSSI was less than in the group with past suicidal attempts only. These findings are consistent with previous studies (
26) that have indicated that adolescents with past suicidal attempts are more prone to subsequent suicide behaviors. Additionally, as people’s experience with death cues, such as blood or the pain of self-injury increase, they become more prone to suicide risk (
27).
A regression model indicated that an inadequate self, hated self, difficulty in impulse control and frequency of NSSI predicts a 50% variance of suicide probability. Our results were consistent with a previous finding (
16) that confirmed the role of self-criticism as a main risk factor for engaging in suicide behaviors (
16). Some forms of self-criticism, such as the inadequate self have greater association with suicide probability. According to the evolutionary model of self-criticism (
18), self-criticism triggers threat and defensive emotions and behaviors, which lead to negative emotions that are difficult to regulate; thus, different kinds of psychopathology, like suicide behaviors, occur.
Although a zero-order correlation has revealed a significant association between difficulties in emotion regulation skills and suicide probability (except the difficulty in awareness subscale), in the regression model, only impulse control problems remained a significant predictor of suicide probability. This finding especially supports prior findings that showed impulsive adolescents are more inclined to suicidal attempts without prior planning (
28). Our results did not confirm previous findings about the relationship between difficulties in emotion regulation skills and suicide ideation and behaviors (
14). According to a previous study (
14) of the emotion regulation subscale, only the perceived inability to access emotion regulation strategies predicted suicide ideation. It should be noted that we used a global index of suicide probability that consisted of ideation and inclination to suicidal attempts, rather than merely suicide ideation. So, it could be concluded that adolescents who have difficulty in controlling their impulses were more prone to suicide ideation and attempts.
Another predictor of suicide probability in the present study was the frequency of NSSI. This finding support previous studies, which have reported a significant association between NSSI and the tendency to suicide ideation and behaviors (
6). However, it does not mean that every kind of NSSI leads to an increase in suicide probability. There have been different kinds of adolescents who engage in NSSI. Many of them engage NSSI just a few times, but a minority of adolescents who frequently use NSSI exclusively as a coping mechanism against any kind of life distress were more prone to act on their suicide ideations (
28). Additionally, the association between NSSI and suicide probability can be explained based on Joiner’s interpersonal theory of suicide (
26). According to this theory, burdensome feelings and a loss of social belonging leads to suicide ideation, but the most determining factor for acting on suicide ideation is the beginning of harming oneself and decreasing fear of suicide. The persons who habituate to different kinds of self-harm are more capable of acting on suicide ideations. It can be concluded that increasing frequency of NSSI leads to suicide probability by acquiring the ability to engage fearlessly in lethal self-harm.
In sum, the present study indicates that adolescents with a history of NSSI and suicidal attempts, compared to a NSSI-only group, were more prone to subsequent suicidal attempts, because they have more suicide ideations, even after passing several years without engaging in a suicidal attempt. Additionally, our findings revealed that self-criticism, impulse control difficulties, and the frequency of NSSI can predict suicide probability in adolescents with a history of childhood maltreatment. It should be noted that this study had a number of limitations. First, the design of this study was cross-sectional, and only self-report instruments were used for assessing our variables. Second, these findings were based exclusively on adolescents who had a history of childhood maltreatment, so they cannot be generalized to other adolescents in normal population or inpatient setting. Future studies should consider the role of these predictors of suicide probability while controlling for other known risk factors for suicidal attempts.
Adolescents with a history of childhood maltreatment, even after acute phases of suicide and hospitalization, are more prone to subsequent suicidal thoughts or behaviors. The risk of subsequent suicidal attempts is higher in adolescents with suicidal attempts and NSSI than in adolescents with NSSI only. Negative feelings about the self, like feelings of inadequacy or self-hatred, were a very important risk factor that can predict a great deal of variance in suicide probability. This study also showed that, among six dimensions of difficulties in emotion regulation skills (
11), impulse control problems were a significant and stable predictor of suicidal attempts. So, psychological interventions should address impulse control problems in programs designed to prevent suicidal attempts. Adolescents who used NSSI frequently also are more prone to suicidal attempts. This association may be caused by their habituation to self-harming, which increases the risk of lethal self-harm. Indeed, according to the results of this study, it could be concluded that accepting one’s self, instead of criticizing the self and overcoming impulse control problems, can decrease rates of suicide probability in adolescents with a history of childhood maltreatment.