Background
Non-suicidal self-injury(NSSI) is generally defined as “the direct, deliberate destruction of one’s own body tissue without the intention of suicidal intent” [
1], including cutting or scratching the skin, burning/branding with cigarettes/lighters, scalding, striking oneself or other hard objects, banging limbs/head and hair pulling, et al. [
2]. Based on previous studies, DSM-5 provided a more accurate definition of NSSI, that is, in the last year, an individual has been engaged in a behavior that intentionally causes bleeding, bruising, or pain on the body surface for 5 or more days, but only causes slight or moderate physical injury [
3]. As one of the public health problems recognized globally, NSSI has provoked concern among health professionals, researchers, social workers and welfare workers, teachers, other professionals and affected families [
4].
Estimated prevalence of NSSI vary widely as due to a number of factors including the time since last episode of NSSI, the number of NSSI episodes to be recognized, research tools, as well as different study areas and populations [
5]. Benjet et al. found that the lifetime prevalence of NSSI was 18.56%, and the annual prevalence was 3.19% in a sample of 1071 Mexican residents of young adults [
6]. In Canada, estimated prevalence range from as low as 7% [
7] of student samples to as high as 77% [
8] of clinical samples. As a coping strategy for maladaptive individuals [
9], NSSI are more prone to be seen in clinical populations, especially in patients with depression or bipolar disorder who have poor abilities of emotional regulation and coping [
10]. A recent study observed that about 37 and 52% of patients with depression and bipolar disorder had engaged in NSSI at least once, respectively [
11]. Fang et al. found that 38.6% of Chinese patients with depression had committed NSSI in the past year [
12]. Although there have been a few relevant studies in China, the evidence on the prevalence of NSSI is still sparse and heterogeneous due to the differences in sample sources and definitions of NSSI [
13,
14]. It is necessary to carefully design studies to help better understand the epidemiology of NSSI in Chinese patients with depression or bipolar disorder.
NSSI leads to a variety of serious consequences, including physical injury [
15], negative emotional experiences and a decline in learning ability, work efficiency [
16], which prompted researchers to explore the risk factors relate to NSSI. A study proposed that young individuals were more prone to conduct NSSI [
17]. However, the evidence on whether NSSI changes with age is insufficient. Moreover, there is contradictory evidence about whether there have a sex difference in NSSI with some studies reporting a higher prevalence among female [
18] and others finding no sex difference [
19]. Also, NSSI was uniquely associated with marital status, employment status, socio-economic status. Nevertheless, findings should be cited with caution [
20]. Tschan et al. presented that the educational level of parents was relate to NSSI [
21]. Besides, there may also be a link between impulsivity and NSSI [
11], which may be more pronounced in individuals with depression or bipolar disorder than in the general population [
22]. A new study revealed that cannabinoid use was connected with an increased prevalence of NSSI by elevating Δ
9- THC/CBD balance [
23], which makes us to think about the relationship between substance abuse experiences such as alcohol, cannabinoid and NSSI. To date, the existing literature is inconsistent with regard to whether the incidence of NSSI is related to adverse childhood experiences(ACEs). In earlier times, Glassman have failed to find a significant association between NSSI and ACEs [
24]. However, new studies provided new clues. In a meta-analysis that included cross-sectional, longitudinal, and retrospective studies published in the same year, Serafini et al. observed that the increased vulnerability to NSSI seems to be related to ACEs [
25].
Whereas studies from other countries have investigated the prevalence of NSSI and risk factors of NSSI [
20,
25,
26], including the exploration of patients with depression or bipolar disorder [
5,
11]. So far, few studies within the Chinese context have investigated the prevalence of NSSI and the risk factors for NSSI among patients with depression or bipolar disorder. Almost all of the few existing studies on NSSI in China are from the general population or relied on student samples where the characteristics are far from representative of patients with depression or bipolar disorder. The purpose of this study aimd to: 1) examine the prevalence of NSSI in patients with depression or bipolar disorder in China, and 2) determine the risk factors for NSSI.
Discussion
In terms of NSSI, there have been a few clinical studies involving patients with depression or bipolar disorder in Western countries [
5,
38], however no such study was conducted in Chinese populations. This was the first study to investigated the prevalence of NSSI and risk factors for NSSI in patients with depression or bipolar disorder in China. Moreover, our findings indicated that a large number of patients with depression or bipolar disorder had engaged NSSI in this sample, and certain demographics, impulsivity and ACEs was associated with NSSI among patients with depression or bipolar disorder in China.
In the present study, our results of prevalence of NSSI was 62.2%, which was slightly lower than the prevalence of NSSI(77%) in a Canadian study among clinical populations [
8]. Equally, Weintraub et al. [
11] found that about 37% of patients with depression and 52% of patients with bipolar disorder had at least one NSSI, which was also higher than the results of this study(34.3 and 27.9%, respectively). The discrepancies in estimates of the prevalence of NSSI may be relate to different sample sources and numbers, various assessment tools, wording of instructions, time frame for raising questions and data collection procedures. As mentioned above, the incidence of NSSI is higher in patients with depression than in patients with bipolar disorder(34.3% vs 27.9%). Depression is a group of prominent and persistent low mood as the main features of the clinical syndrome [
39]. Affected by the low mood, depressed patients often feel extremely sad, self abasement, decadent and pessimistic, and then the germ of an idea of NSSI took root in patient’s mind. In regard to the method of NSSI, patients of different sex tried NSSI in different ways. Barrocas [
40] found ‘hitting against hard objects’ to be the most common way that male injury themselves, while Brunner [
41] found ‘cutting’ to be the most common way that female injury themselves. These findings of ways of NSSI are generally consistent with this present study. Explainations for sex differences are yet to be examined and may be due to personality differences and cultural differences [
42].
It has been suggested that demographic characteristics and clinical features(age, sex, marital status and diagnosis, etc) should be considered when interpreting results of any NSSI research [
4]. Contrary to expectation, there was no statistical significance between patient’s sex, education, residence and the incidence of NSSI in patients with depression and bipolar disorder(
P>0.05), which are contrary to Tang’s study [
37]. On the one hand, this study included patients with depression and bipolar disorder. Compared with the general populations, their ability of emotion regulation and coping with life events is limited [
43]. Whether male or female patients, the impact of negative life events and the failure of emotion regulation will stimulate the patients’ desire to conduct adopting stress reduction behaviors (e.g., NSSI), so as to escape from feelings and thoughts associated with stressful life events [
44]. This may be the reason why there was no difference in the occurrence of NSSI between male and female patients in this study. On the other hand, this present study recruited patients from two psychiatric hospitals in Beijing, most of whom came from Beijing or the affluent urban families from other cities. Most included patients had better educational opportunities and higher level of education. The patients included in this study only reflect the situation of a small part of China, so the generalization of this finding is limited. Caution should be kept in quoting this findings.
To our surprise, statistical significance between substance abuse experience and the incidence of NSSI in patients with depression and bipolar disorder was not found(
P>0.05), which was partially inconsistent with Escelsior’s findings [
23]. This divergence is related to the fact that the substance abuse included in this study is not confined to cannabis, but also extended to various types of substance abuse. The number of patients with each type of substance abuse is limited, and the types of substance abuse are not concentrated, so we can not analyze all kinds of substance abuse experience separately, which may affect the results of this study. Notably, cannabis, inhalants, etc. for personal use are not allowed in Chinese laws [
45], so the unwillingness of reporting such experiences hinders our further exploration. Different from other studies [
46,
47], there is no significant difference in the left-behind experience between three groups, which may be related to the fact that most of the samples are from Beijing rather than remote and poor areas As the capital of China, Beijing has the ability to solve the employment problem without local people going out to look for employment opportunities [
48], which was also reflected by the high educational level of patients and high monthly family income in this study.
By multivariate regression analysis, we proved that young, unemployment, single, a higher monthly family income, long duration of illness, impulsivity and ACEs were risk factors leading to NSSI of patients with depression and bipolar disorders. First of all, this study showed that younger participants(18 ~ 30 years old) had a higher risk of NSSI, which is consistent with Preyde’s findings that NSSI is more prevalent in young patients with psychiatric disorders due to their difficulty in emotional regulation, adaptive ability and interpersonal relationships [
8,
49]. Next, the unemployed patients with depression were more likely to conduct NSSI. Compared with the employed patients, the unemployed patients can not have a relatively fixed incomes and stable personal relationships for a long time, which implied that it is inadequate for patients to get financial support and emotional support [
50], increasing the risk of NSSI [
51]. Moreover, we found increased risks of NSSI in depressed patients related to have a higher monthly family income. A higher monthly family income reflects that the family members who have limited spare time invested so much time and effort in work, which resulted in the limited time to get along with the patients, and then neglected the patients [
52]. Due to the untimely response to the emotional needs of patients, the corresponding emotional support is insufficient, and patients are more likely to seek psychological comfort through NSSI. These findings highlight the importance of positive parenting style to NSSI onset, with implications for prevention of NSSI onset among depressed patients [
53].
In this present study, marital status is one of the important factors affecting NSSI of patients with bipolar disorder, that is, single patients are more likely to engaged in NSSI, which has been repeatedly emphasized in previous studies [
54‐
56]. It is widely known that family support obtained by stable marriage status was most salient in onset, maintenance and cessation of NSSI [
55]. Stable marriage status provides social, economic and emotional support to patients and reduces their sense of isolation by providing them with opportunities to interact with society, and spouses of married patients play an important role in monitoring their partners’ health-related behaviors for a long time, encouraging them to develop healthy lifestyle [
54]. Besides, long duration of illness(more than 10 years) was the risk factor for NSSI in patients with bipolar disorder. It is a long-term process to develop from unipolar depression to bipolar disorder [
57]. During this period, the patient experienced repeated fluctuations of the disease. Affected by the symptoms or discontented treatment outcome, the patient felt hopeless and desperate, and then increased the possibility of NSSI. In addition, we proposed that impulsivity remained a significant influence on NSSI in patients with bipolar disorder, and this finding was supported by Lin et al. [
58]. Individuals with strong impulsivity tend to act impulsively in the face of negative emotions, because the short-term gain of emotional regulation is the most important goal at present [
59]. Since NSSI has been proved to be an effective method for individuals to regulate negtive emotions, individuals with strong impulsivity are more willing to participate in NSSI to obtain the direct benefits of NSSI(i.e. emotional regulation) [
60]. At the same time, it is suggested that NSSI is a rapid, effective, and easily implemented method of regulating one’s negative emotion [
58]. Consequently, impulsivity may be strongly related to NSSI.
In recent years, several studies found that individuals reporting ACEs were tied up with NSSI [
61,
62], which were consistent with this study. What’s more, ACEs can be strongly associated to NSSI among patients with depression and bipolar disorder [
5]. Although heritability is often emphasized, NSSI is associated with environmental factors [
63]. As a series of negative life events, ACEs will affect the individual’s psychological development and emotional regulation [
64]. And the patients with depression or bipolar disorder already have weak ability of emotional regulation [
65]. Therefore, patients with ACEs can relieve their negative emotions by adopting NSSI. This also explains why ACEs has a subtle effect on the occurrence of NSSI in patients with depression and bipolar disorder. Serafini’s study also highlighted the specific role of sexual abuse in the development of NSSI [
25], so exploring specific associations between various types of ACEs and NSSI would be the next step. So far, some existing studies have investigated the mediators or moderators in relationship between ACEs and NSSI [
66]. It is necessary to explore the specific connections between ACEs and NSSI, especially in the Chinese backdround.
Implications
This study investigated the prevalence of NSSI and its risk factors among patients with depression and bipolar disorder in China. Primarily, we have obtained the not encouraging prevalence to arouse the attention of domestic medical staff, relevant scholars and the public. That is to say, the coping strategies for NSSI should not be confined to hospitals but extended to the communities and families. Then, by comparing the demographic data, impulsivity and ACEs between groups, the relevant influencing factors were found, which can provide support for the exploration of prevention, treatment and etiology of this group. Eventually, the risk factors for NSSI was identified by multivariate regression analysis. Except for the assessment of general demographic data, assessment procedures of mental health may need to include an assessment of impulsivity and ACEs to more fully evaluate NSSI. A combination of the risk factors mentioned above and diagnosis of depression or bipolar disorder among patients who conduct NSSI can also alert medical staff to develop targeted interventions aimed at helping these patients and their families with emotion regulation skills so as to cope with past negative experiences and consequently improve their mental health and well-being. From an academic point of view, this study further confirmed the correlations between NSSI and some factors in patients with depression and bipolar disorder, further supported the conclusions of some scholars. This study also offered new thought for scholars of various contries to guide them to carry out more scientific and targeted research. Notably, future studies should focus on the origin of NSSI as opposed to its characteristics, in order for professionals to be able to prevent the issue.
Limitations
Several limitations of the current study need to be acknowledged. Initially, the participants included were patients in two hospitals in Beijing. As the capital of China, Beijing will attract patients from all over the country, the samples are mainly Beijing native. Considering that China is a vast country with diversified social economy, the source of sample would limits the generalizability of these findings to other cities and rural areas of China. Second, we employed retrospective self-report questionnaires, and there is no independent confirmation, which might mean our data were not sufficiently objective. Participants may forget, suppress or even identify with their experiences as they grow older and more experienced. Therefore, these data may be affected by bias to some extent. Third, an exploration of testing the directionality of the relationships is not allowed in the present study because of the design of cross-sectional. There may be a great deal of analyses and the possibility that some of the correlations were obtained by chance. Taking into account these limitations, additional studies are needed to investigate the NSSI and tease apart the association between NSSI and some factors in order to determine how generalizable the results of this study would be to other psychiatric hospitals from diffirent regions in China. Such studies should employ a large sample, multicenter, longitudinal design, and adopt tools other than self-report questionnaire(e.g., expert opinions or other objective evidence). And we should remain cautious in drawing causal inferences regarding the relationship between NSSI and some factors.
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