In this study, non-suicidal self-injury had the highest incidence among high school students, regardless of sex, with a high incidence among depressive disorder patients with a history of smoking and drinking. NSSI partially mediated the risk of suicide in depressed patients.
Epidemiological studies have shown that non-suicidal self-injury is a serious problem in adolescence, with a lifetime prevalence of 17–60%, with a peak in mid-adolescence (age 15–16) and a gradual decline in late adolescence (age 18 years). Adolescence is the most prevalent stage of NSSI, and the age distribution of NSSI shows an inverted V-shaped trend, with the highest reported rate of NSSI in the 15–16 age group[23, 24]. One study investigated 1283 junior high school students in Wuhan City and found that the average age of first self-injury in students with NSSI was 12.35 ± 3.12 years, 57% of them were aged 12–15 years old. The incidence of NSSI gradually decreased with the increase of age. It was also believed that NSSI behavior would naturally ease with age in mature patients, and only adolescents with obvious emotional problems would require treatment. In this study, the incidence of NSSI was highest in high school or secondary school adolescent students (15–18 years old) and gradually decreased during the college years (after 19 years old). This problem is influenced by various factors, including social predisposition, interpersonal relationships, coping with stressful events, neurobiological characteristics, disorders of responsive regulation in childhood, and adverse experiences. Although there is a significant decline or cessation of non-suicidal self-injury behavior between late adolescence and early adulthood, adolescents who repeatedly engage in non-suicidal self-injury behavior are at an increased risk of long-term mental health problems, suicide, and risky behaviors. In terms of psychosocial factors, adolescence, a period of continuous brain development, is associated with increased impulse control and emotional overreactions. They are more likely to be influenced and instigated by their surroundings. Foreign research shows that the searches for non-suicidal self-injury behaviors on websites exceeded 40 million times in one year. Videos and photos of this behavior were viewed over one million times, which is significantly correlated with the annual increase in non-suicidal suicidal behaviors. If an individual’s relatives, classmates, or friends have carried out NSSI, the risk of the occurrence of the same behavior will greatly increase for such an individual, which may also be related to subcultural factors[25].
At present, it is difficult to determine whether sex differences influence the detection rate of NSSI behaviors at home and abroad. For example, Chinese researchers have found that the incidence of NSSI in males is higher than that in females. Huang et al. showed that the detection rates of NSSI in males and females were 23.5% and 19.6%, respectively[26]. Furthermore, a meta-analysis with a larger sample in China showed that male students were more likely to experience NSSI than female students. In contrast, other studies have found that the detection rate of NSSI is higher in females than in males[27]. Moreover, the results of other studies showed no statistically significant difference between men and women[9, 28]. This finding is consistent with the results of the present study. Currently, there is no consensus on the effect of sex on the occurrence of NSSI. However, the age of the participants surveyed was related to NSSI. The incidence of NSSI was higher among women in middle and high school, whereas it was more common among men in college[9, 29]. According to a survey conducted by Hasking on adolescents aged 12–18 years, there was no difference in gender NSSI behavior. However, when surveyed again 11.7 months later, they found that the detection rate in females was significantly higher than that in males[30].
Smoking and drinking, which are bad habits of adolescents, were more likely to occur in NSSI patients. Domestic and foreign studies have found that adolescents with NSSI have bad habits of smoking or drinking[31]. Drinking and smoking are common among adolescents because of their self-control difficulties[32, 33]. In 2014, the U.S. Health Service reported that more than 600,000 middle school students and 3 million high school students smoked[34]. Moreover, a previous study reported that the proportions of former and current smokers in China were 33.83% and 7.93%, respectively[35]. Similarly, alcohol, a typical substance, is used by teenagers worldwide, and China is no exception. Approximately one-quarter of the teens reported drinking alcohol in the last 30 days of this study[36]. There is an established correlation between risky drinking and the manifestation of NSSI[37].
In China, the incidence of depression among young adults is increasing. This situation has become more severe during the COVID-19 pandemic[38, 39]. Similarly, a survey conducted in the Yellowstone area of America found that the year 2021, the year of the COVID-19 epidemic, saw a marked increase in the incidence of depression among adolescents[40]. Suicide is a fatal outcome for people with depression and depression has worsened adolescent mental health and increased suicide rates globally since the pandemic[41]. A large case-control study in China confirmed that depression, particularly depression severity scores in the two weeks before death, are important predictors of suicide[42]. According to the interpersonal theory of suicide, suicidal intention and capacity are preconditions of suicide[43]. Suicidal intention comes from self-guilt and self-belonging frustration, which are clinical characteristics of patients with depression. Reducing self-guilt and self-belonging frustration in patients with depression can reduce the occurrence of suicidal behaviors[44].
The incidence of NSSI is the highest in adolescents with depression. The estimated incidence of NSSI among those diagnosed with depression was 62.6% (56.2–67.9%)[45–49]. In this study, the incidence of depressive disorder was 34.6%. This is lower than that in previous studies[45–49], considering that some adolescents may be reluctant to report self-injury behavior in face-to-face scale assessments or there may be recall bias. Depressive mood is an important predictor of future NSSI development[45]. According to the theoretical model of NSSI, mood fluctuations are the initiation and recurrence factors of NSSI, particularly negative mood, which is a prerequisite for the occurrence of NSSI. Some self-reported studies have shown that individuals' depressive mood increases before NSSI, while their depressive mood is relieved, and new feelings are obtained after NSSI is concluded[50]. In addition, NSSI may be a predictor of new-onset depression in adolescents[51]. Depressive mood plays an important role in the occurrence and recurrence of NSSI.
In this study, NSSI partially mediated the risk of suicide among patients with depressive disorder. This is consistent with the results of previous studies[52]. NSSI is not only directly related to depression severity scores, but also plays a partial mediating role in the regulation of suicide risk in patients with depressive disorder. Patients with high depression scores have a limited ability to withstand external stimuli or problem-solving coping strategies; therefore, depressed patients desire to quickly release negative emotions through NSSI negative coping strategies[53]. NSSI only satisfies depressed individuals for temporary and urgent self-regulation. According to the reward mechanism (acquired theory), a depressed person repeatedly uses this negative approach to achieve temporary satisfaction[54]. If the desired effect is not achieved, the depressed person will resort to more serious self-injury to achieve the desired effect and even commit suicide[55]. In addition, NSSI may aggravate depressed patients' negative self-perceptions such as low self-esteem and self-blame, which further increase the probability of suicide attempts[56]. This may explain why NSSI is an important predictor of suicide.
LIMITATIONS
Participants were enrolled as first-time patients in the Psychological Outpatient Department of the hospital. A selection bias may have limited the generalizability of the results. The results may have been influenced by the fact that adult psychology outpatient consultations with patients over 14 years of age (including 14 years of age) and patients under 14 years of age are required to attend pediatric outpatient consultations. There was only one association among the three and no causation. First, the sample size was small and limited to adolescents with depression. Possible session bias may have occurred due to self-reporting. Some adolescents may also have been reluctant to report self-harming behaviors.