Distinct Clinical Characteristics Correlate Network of Suicide Attempters in Adolescent Major Depressive Disorder with Non-suicidal Self-Injury (Preprint)
Authors: Liu Xin-an , Pan Jiyang , Peng Bo , Wang Ruoxi , Zuo Wenlong , Zhang Yingli , Deng Chunshan , Liu Haitao , Liao Jiwu , Zhao Weitan , Li Jinmeng , Dai Lei 
Published: March 2023

BACKGROUND

Major depressive disorder (MDD), the leading cause of disability worldwide, is regarded as the main cause of global burden of disease in youth. MDD is a common multifactorial, recurrent, and chronic psychological illness and one of the major risk factors for suicide attempts (SA) and non-suicidal self-injury (NSSI). NSSI refers to behaviors causing deliberate destruction or damage to one’s body without a conscious suicidal intention, it has a high incidence in both adults and adolescents and is associated with many psychiatric disorders.
Suicide is one of the most serious consequences of mental illness and the fourth leading cause of death among adolescence. According to the WHO (2021), more than 700,000 people die by suicide every year globally (Suicide worldwide in 2019: global health estimates). Previous studies have reported that more than 90 percent of suicides occur in the context of depression, such as MDD. The severity of depression was not only positively correlated with the probability of NSSI, but also laid a mediating effect on stressful life events and NSSI. Therefore, MDD with NSSI are considered as potential suicidal population. Notably, NSSI is highly prevalent and frequently co-occur with suicidal attempt in both clinical and non-clinical populations of adolescents, and has been regarded to predict future suicide attempts.
Since suicidal behavior usually begins with self-injury, which is common among young patients with depression, it is critical to investigate risk factors for suicide in MDD with self-injury behaviors. Behavioral abnormalities have been studied, such as executive dysfunction in the depressed adolescents with NSSI and patients of bipolar disorder with suicidal ideation, impaired decision making in patients with SA; based on the assessments of various behavioral symptoms, a number of statistical or actuarial scales have emerged to aid clinicians predict and manage suicide risk. Studies of biomarkers and neural markers of suicide risk have been reported including neural connectivity as a predictor of response in NSSI after psychotherapy or biologically-informed approaches; the low level of cholesterol in sera as a potential biomarker of suicide in patients with MDD and suicidal behavior. Blunted HPA axis activity and dysfunctional adaptive immune response are also associated with increased suicide attempts. Elevated inflammation as presented as increased CRP level in sera was found in patients with SA. Evidence also supported the association between dyslipidemia and suicide risk.

Massive studies have been conducted regarding the differences of psychological characteristics, immunity, and metabolic properties between patients with NSSI and suicidal ideation, and the correlation between the immune function and psychological properties was found in patients with SA. Previous studies mainly focused on the investigation of clinical differences between suicide and non-suicide patients, however the results were often inconsistent due to the limited reliability of univariate analysis for the sample heterogeneity in clinic.

OBJECTIVE

In this study, we aim to investigate the differences and correlation network of multiple psychological and biochemical indicators of suicidal and non-suicidal MDD with NSSI in adolescents. The distinct correlation profile may offer cues for prediction of suicide risk in adolescent MDD with NSSI.

METHODS

This study was approved by the Ethical Committee of Shenzhen Kangning Hospital (Approved No. 2020-K033-01). One hundred and thirty patients with major depression associated with NSSI were recruited from the Department of Depressive Disorders, Shenzhen Kangning Hospital between March 2020 and January 2021. Participants were young adults aged between 12–35 years old with a history of self- injury for at least 1 year. We collected relevant data from the included subjects: i) Ottawa Self-injury Inventory (OSI) ; Beck Depression Inventory-Ⅱ (BDI-Ⅱ) ; State Trait Anxiety Inventory (STAI); Barrat impulsiveness scale (BIS-11); Difficulties in Emotion Regulation Scale (DERS); State-Trait Anger Expression Inventory (STAXI-2); Borderline Symptom List (BSL-23); Childhood Trauma Questionnaire (CTQ); Ethics Position Questionnaire (EPQ); The Defense Style Questionnaire (DSQ) and Copying Style Questionnaire (CSQ); ii) peripheral blood samples for biochemical assessment. Informed written consent was obtained from all the included participants with their knowledge of this study procedures. The detailed information of the included subjects is displayed in Tables 1-3.

With education for at least 6 years, participants were assessed by a trained psychiatrist in the Mini-International Neuropsychological Interview (M.I.N.I.) to meet the DSM-5 diagnosis of MDD. All included patients had a history of self- injury for at least 1 year. Eighty of the 130 participants had suicide attempt in the last year, were included in the group of suicide attempters (‘NSSI+SA’). Fifty people were classified in the non-suicidal self-injury group (‘NSSI’). All included participants had no major physical illness (including acute or chronic infectious diseases and heart, liver, kidney, endocrine, and immune system diseases) or other psychological disorder; they did not have significant factors affecting their immune function and hormone secretion (such as taking immunosuppressant and glucocorticoid). None of the patients were using lipid-lowering medication or sugar-lowering medication. Participants were excluded if they had a major physical illness or other psychological disorder or if they had significant factors affecting their immune function and hormone secretion. Written consent was obtained from participants or their family before the start of the study.

Determination of biochemical and immunological indicators
Blood samples of patients were collected between 7:00 and 8:00 am. After a 12‑hour fasting. 5 mL of venous blood was extracted and centrifuged at 2500 r/min for 10min. The supernatant was obtained as the serum for further analysis. For the serum lipid, cortisol and blood glucose concentration enzyme linked immunosorbent assay (ELISA) methods were used; the levels of CRP and ACTH were measured by immunoturbidimetry.

Behavioral Assessment
OSI
OSI is a scale used to assess non-suicidal NSSI behavior. The scale consists of a series of independent subscales to assess intention and frequency of NSSI behavior, motivation for initial and ongoing NSSI behavior, and addiction and other NSSI behavioral characteristics [28]. In this study, we utilized the first item in the OSI scale to evaluate the frequency of NSSI in the past one year and one month, and the second item to evaluate whether the patient had suicidal behavior.

BDI-Ⅱ
BDI-II is a commonly-used, well-validated self-report measure of depressive symptoms. The analyses based on scores that rank depression levels. Its Chinese version has been widely used to assess the symptoms and severity of depression in patients with mental illness and the general population [29].

STAI
STAI consists of two subscales, one measuring state anxiety (STAI-S) and the other measuring trait anxiety (STAI-T). The total score on each subscale ranged from 20 to 80, with higher scores indicating more anxiety symptoms. STAI has good applicability in Chinese population [30].

BIS-11
BIS-11 is a scale used to measure impulsivity in an individual's behavior. It consists of three subscales (motor, attentional, non-planning) with a total score of 30-120, with higher scores indicating higher levels of impulsivity. BIS-11 showed good psychometrics in Chinese population samples [31].

DERS
DERS is an effective instrument to measure the difficulty of emotion regulation - the difficulty of emotion regulation scale. Among them, there are 6 factors: difficulty in emotional response acceptance, difficulty in goal orientation, difficulty in impulse control, difficulty in emotional awareness, difficulty in the use of regulatory strategies and difficulty in emotional understanding. The higher the score, the more serious the difficulty of emotional regulation, the lower the level of emotional regulation ability. Studies have confirmed its applicability in the Chinese population samples [32].

STAXI-2
STAXI-2 is currently the preferred tool for evaluating the experience and expression of anger, which provides a simple and objective scoring method for the experience, expression and control of anger. The scale can measure state anger, trait anger, and anger expression and control respectively.

BSL-23
BSL-23 [33] is a self-rating scale for assessing marginal symptoms. The total score is in a range of 0-92. The higher the score, the more severe the marginal symptoms. BSL-23 has good psychometrics in Chinese population samples [34].

CTQ
CTQ was developed by Bernstein et al., which is currently recognized as one of the most effective tools for measuring childhood abuse [35]. The scale includes both abuse and neglect. Among them, abuse includes emotional abuse, physical abuse and sexual abuse. Neglect also includes emotional neglect and physical neglect. The Chinese version of CTQ has been shown to have adequate psychometric properties [36].

EPQ
The EPQ questionnaire was compiled by the British psychologist Professor Eysenck and others. The children's version and the adult version are applicable to subjects aged 7-15 and over 16 years, respectively. Both versions of the questionnaire included four subscales: internal and external orientation, mental quality, spiritual quality, and concealment. In this study, the children version and the adult version of the questionnaire were respectively used to test the subjects in the corresponding age range. The questionnaire has high reliability and validity in Chinese population.

DSQ
Because this scale is suitable for people with different cultural backgrounds and has good reliability and validity, DSQ is one of the most widely used scales for evaluation of defense mechanisms at home and abroad. The scale includes four subscales: immature defense style, mature defense style, intermediate defense style and cover up.

CSQ
The questionnaire was compiled by Chinese psychologists, based on the content of the questionnaire used by domestic and foreign experts to study coping and defensive behaviors, as well as the theory of ‘coping’. The questionnaire consists of 62 items, including six subscales including retreats, illusion, self-blame, help seeking, rationalization, and problem solving. Each item had two optional answers, and the higher the score, the more likely it was to respond in one way or another. The questionnaire was confirmed to have good reliability and validity and widely used in Chinese population [37].

Statistical analyses
Preliminary analyses examined data for outliers and determined if data met assumptions of normality and linearity as appropriate. Pearson correlations and independent samples t-tests were performed to determine interrelationships between various indicators by Matlab. Multivariate regression analysis was performed including all the variables which were significantly associated with SA in Univariate analysis (P < 0.1) using Backward LR method (P < 0.05). T-test and regression analyses were performed by SPSS version 26.0. The statistical significance was set at two-tailed P < 0.05.

RESULTS

Sample characteristics
The demographic characteristics of 130 participants diagnosed with MDD with NSSI are summarized in Table 1. Among all the 130 participants, 80 individuals (61.54%) had SA, that were included as the ‘NSSI+SA’ group; 50 subjects (38.46%) had only experienced self-injury but no suicide attempts, who were classified into the ‘NSSI’ group. Strikingly we noticed that, among the 130 MDD with NSSI, the proportion of patients who had suicide attempts was higher than those who had only self-harmed, suggesting that the patients with NSSI may be at high risk for suicidal behaviors. The mean age of patients in the group of ‘NSSI+SA’ was 20.2 years, 2.12 years younger than those in the ‘NSSI’ group. It is worth noting that, there was a higher proportion of females versus males in patients of both ‘NSSI+SA’ and ‘NSSI’ groups.

Clinical differences between participants of suicidal and non-suicidal adolescent MDD with NSSI
Table 2 shows the scores of multiple behavioral assessments as psychological indicators in both the ‘NSSI+SA’ group and the ‘NSSI’ group and the differences between these two groups. To comprehensively assess the psychological indicators of MDD patients with NSSI, 44 psychological indicators were derived from 11 clinical scales. In contrast, seek help (P = 0.022), BIS-11 total scores (P = 0.043), attentional impulsiveness (P = 0.049), non-planning impulsiveness (P = 0.039) and clarity (P = 0.037) were significantly different between the groups of ‘NSSI+SA’ and ‘NSSI’. In addition to clarity, the other four psychological indicators were related to impulsiveness, which is consistent with the previous work showing the link between impulsivity and self-harm behaviors [38]. Here in our data, patients in the ‘NSSI+SA’ group were shown more impulsive compared to subjects who only had ‘NSSI’.

Lower serum levels of CRP and cortisol in suicidal compared to non-suicidal participants of adolescent MDD with NSSI
The values of biochemistry indicators in blood samples are shown in Table 3. The mean of glucose was 4.82 ± 0.42 and 4.79 ± 0.56 in suicidal attempt and non-suicidal patients respectively (P = 0.666), the mean of TG was 1.24 ± 0.60 and 1.20 ± 0.81 in ‘NSSI+SA’ group and in the ‘NSSI’ group, respectively (P = 0.786), with statistically insignificant difference. In addition, there were also no statistical differences in TC, HDL, LDL and ACTH between the two groups. In contrast, cortisol (P = 0.024) and CRP (P = 0.005) were significantly different between the ‘NSSI+SA’ and ‘NSSI’ groups and shown lower levels in the group of ‘NSSI+SA’.

Association network profiles of psychological and biochemical indicators in non-suicidal and suicidal patients in adolescent MDD with NSSI
We performed regression analysis and found that the frequency of self-injury in the past month was a predictor for suicidal behavior (OR: 1.588, 95% CI: 1.006-2.508, P = 0.047); and CRP was also found among biochemical indicators as a predictor for suicidal behavior in MDD with NSSI (OR: 0.392, 95% CI: 0.200-0.767, P = 0.006). Further, the correlation analyses were performed among the 63 indicators in both the ‘NSSI+SA’ group and the ‘NSSI’ group including basic information, biochemical indicators and psychological indicators (Fig. 1A). A total of 628 correlations were detected in the ‘NSSI+SA’ group, and only 382 correlations were detected in the ‘NSSI’ group (Fig. 1B). According to our Spearman heatmap correlation analysis, the linear correlations between specific indicators and unique correlation heatmaps were observed between the ‘NSSI+SA’ group and the ‘NSSI’ group (Fig. 1 C and D).

We then further explored the linear correlations of the biochemical and psychological indicators and specific correlation heatmaps were observed between the two groups (Fig. 2A and B). When compared the two types of indicators, CRP was negatively correlated with mature defense (R = -0.29, P = 0.0091) in the group of ‘NSSI+SA’, while there was no correlation between them in the ‘NSSI’ group (P = 0.106, Fig. 3A). And there was a significant positive correlation between CRP with emotional neglect (R = 0.287, P = 0.0099) in the group of ‘NSSI+SA’, however, there was no correlation between them in the ‘NSSI’ group (P = 0.0508, Fig. 3B). The positive correlation was also observed between CRP and anger control-out in the ‘NSSI’ group (R = 0.438, P = 0.0015) while it did not exist in the group of ‘NSSI+SA’ (P = 0.318, Fig. 3C). In addition, the levels of glucose and physical neglect were positively correlated (R = 0.306, P = 0.0058) in the group of ‘NSSI+SA’ (Fig. 3D), in contrast, there was no correlation between them in the ‘NSSI’ group (P = 0.483). LDL and anger temperament were negatively correlated in the ‘NSSI’ group instead of the group of ‘NSSI+SA’ (R = -0.383, P = 0.00603, Fig. 3E). The level of ACTH was observed positively associated with anger expression-out in the group of ‘NSSI+SA’ (R = 0.223, P = 0.0469), while negatively correlated with anger expression-out in the ‘NSSI’ group (R = -0.358, P = 0.0107, Fig. 3F).

To further reveal the discriminative association network features between participants in the ‘NSSI+SA’ group and ‘NSSI’ group among adolescent MDD participants with NSSI, we performed the analysis on the common (Fig. 4A and B) and unique features of association networks of them (Fig. 4C and D). More complex correlations were observed among psychological indicators related to expression of anger, impulsivity and immature defense in the ‘NSSI+SA’ group compared with the ‘NSSI’ group. Further analysis on the differences in the association networks of the two groups was carried out and it is worth noting that, participants who had suicide attempt could have stronger correlations between the psychological indicators related to impulsivity and the expression of emotion or anger, as shown in Fig. 5. These correlation networks suggested key roles of impulsivity and anger related behavioral correlates in SA among adolescent MDD with NSSI.

CONCLUSIONS

We analyzed the correlation profile between psychological and biochemical indicators in the two groups among MDD with NSSI. Strikingly we found that the correlation profile is unique to suicide attempters when compared with non-suicidal self-injurers. We observed a statistically significant difference in CRP between suicidal and non-suicidal patients and found correlations between CRP and psychological indicators. It is worth noting that, CRP in sera was negatively correlated with mature defense and positively correlated with emotional neglect in suicide attempters; while it was positively correlated with anger control-out in non-suicidal self-injurers. These results suggest that the level of CRP in sera and the scores of psychological indicators may have differential interplay in MDD with NSSI based on experiences of SA. Our findings suggested that the CRP level in sera may be a key monitor for suicidal ideation in MDD with NSSI.

In addition, we have found in our study that glucose was positively correlated with physical neglect in suicide attempters, and LDL was negatively correlated with anger temperament in non-suicidal self-injurers. Patients with MDD were reported metabolic dysfunction including altered levels of glucose, insulin, and glucagon in the blood. MDD with suicide attempts were reported to have higher glucose levels compared with that in MDD without suicide attempt. It was also reported that the level of LDL in sera is associated with the severity of depression. Suicide attempters older than 40 years were found to have significantly higher level of LDL compared to non-suicidal cases based on a study by Lee and Kim. Therefore the level of LDL in the blood may have the potential as a predictor for suicide attempt in MDD with NSSI which needs to be closely monitored, routinely screened and regularly followed up in these patients.

Furthermore, we aimed to investigate predictors for SA in MDD with NSSI by studying the profile of correlations among blood biochemical and psychological indicators in these patients, considering the surveillance on any single factor may not be sufficient to predict suicidal behavior in the clinic. Besides we found that the score of impulsiveness, the levels of CRP and cortisol in sera have potentials to be risk factors for suicide attempts in MDD with NSSI, we further explored the suicide attempters in adolescent MDD with NSSI had the unique association network of psycho-behavioral and biochemical indicators, in which the correlation is more complex. Our current data also suggested that psychological indicators related to anger and impulsivity in adolescent MDD with NSSI deserves close attention by the clinicians. The correlation profile of psychological and biochemical indicators may offer cues for distinguishing suicide attempters in adolescent MDD with NSSI in clinic.

In sum, although many work has highlighted the potential roles of biochemical indicators in predicting suicidal behavior, our present work suggested that, the complex association network among psychological and biochemical indicators, especially the behavioral correlates for emotional expression could be critical surveillance for predicting suicidal behavior in adolescent major depressive disorder with non-suicidal self-injury.