Entrapment Predicts First-Onset Suicidal Ideation: A Longitudinal Study in Medical Students

Background The prevalence of suicidal ideation among medical students is high. Evidences indicate that entrapment is a predicting factor of suicidal ideation. This study aimed to (1) investigate the prevalence rates of rst-onset suicidal ideation among Chinese medical students, (2) explore the predictive effects of alteration of entrapment on rst-onset suicidal ideation. Methods This longitudinal study was conducted between 2018 and 2019, included 211 new-enrolled medical students in Shanghai. Socio-demographic (gender, major, parents’ income and academic performance), psychological (entrapment, depression, loneliness, defeat, social support and interpersonal needs) variables and suicidal ideation were collected by anonymous questionnaire. Samples were divided into 4 subgroups according to their exposure to entrapment (control, new-onset, reduced and persistent group). The primary outcome, rst-onset suicidal ideation, was de�ned as absent suicidal ideation at baseline but present at follow-up.

what reported.Consequently, exploration of the generation and features of suicidal ideation among medical students to reveal future intervention targets is imperative [6].
Entrapment is a strong motive to escape, with the feeling of being blocked [16] and consists of two components: external entrapment (the feeling of being blocked by external factors such as the living environment, others' opinions, obligations) and internal entrapment (one's internal feelings and thoughts) [15,17,18].According to the integrated motivational-volitional model (IMV model), defeat and humiliation transit to entrapment with certain moderators including poor coping and poor problem solving [19], and then entrapment translates to suicidal ideation with the enhancement or reduction role of motivational moderator [20].Recent years have witnessed burgeoning interest in entrapment as well as its potential mechanism leading to suicidal ideation.For example, in a cross-section study in Chinese adolescents, entrapment was proved to be signi cantly related with suicidal ideation and factors like thwarted belongingness and perceived burdensomeness could reinforce the relationship [21].Furthermore, it has been repetitiously proved that entrapment mediated the relationship between defeat and suicidal ideation, with resilience as a possible alleviating factor [22,23].Nevertheless, though many previous studies have dug into the entrapment-suicidal ideation relationship, few of them focus on medical students, the group of population at higher risk of suicide [24].In addition, most of them are cross-sectional studies [2,20]that only focus on correlation of entrapment and suicidal ideation rather than longitudinal studies that are able to explore alteration of entrapment level in suicidal ideation cases.A 4-month follow-up research was conducted to reveal the role of entrapment in predicting suicidal ideation [25], thus giving us inspiration to probe into the relationship within a longer period and divide the participants into different groups based on altered levels of exposure to entrapment.Another remarkable disadvantage with previous studies is that few of them were conducted in Asia or low-and middle-income countries [26], which account for a large portion of global suicide deaths, revealing the need to broaden the scope of longitudinal research on suicidal ideation in terms of countries and regions.To the best of our knowledge, no such prospective study assessing entrapment alteration as a predictor of suicidal ideation among medical students has ever been conducted.Therefore, a 12-month follow-up longitudinal study has been designed, aiming to (1) investigate the prevalence rates of rst-onset suicidal ideation among Chinese medical students, (2) explore the predictive effects of alteration of entrapment on rst-onset suicidal ideation.

Participants and procedures
The setting of present study was one well-known medical school in Shanghai.All eligible freshmen met inclusion criteria below were invited to participate at the rst year of university for baseline survey(N=656).The progress of investigation was mentioned in our previous study [27].The baseline (T0) survey was conducted from March to May 2018.Since the questionnaire was anonymous, the last four and three digits of participants' identity card number and phone numbers would be collected only for matching purposes.And all eligible freshmen met inclusion criteria were invited again to complete the follow-up survey(T1) at the second year of school (from June to July 2019).
Questionnaire with any missing item was regarded as invalid.Casual samples are also excluded during data processing.Any participant reported ever had suicidal ideation at baseline was excluded.Finally, 12month follow-up cohort was established(N=211) (see Fig. 1).

Ethics
The study was approved by the Ethics Committee of Shanghai Jiao Tong University School of Medicine (SJUPN-201813).Participants were guaranteed that the collected data would only be accessed by the researchers.Once signed informed consent, participants were agreed to participate in this investigation.All participants were free to ask any questions and to withdraw if they did not wish to continue and they were also aware of that the last four and three digits of participants' identity card number and phone numbers would be collected only for matching purposes which could not identify any participant.

Psychological variables
Entrapment.Entrapment was assessed with the Entrapment Scale [28], a 16-item Likert-type questionnaire.The questionnaire was focused on the subjective feeling of entrapment, with every item ranging from 0 (not at all like me) to 4 (extremely like me).Question 1-10 were focused on external entrapment, while question 11-16 concentrate on internal entrapment.A higher sum scored indicated a higher level of entrapment, and the cut-off point was set at 16, the upper quartile of entrapment scores at T0. Participants with entrapment scores higher than 16 were de ned as perceived entrapment status at the time of investigation.The Chinese vision of Entrapment Scale was proved valid and reliable in Chinese medical students [29] (Cronbach's alpha=0.951;range 0-64).
Depression.The level of depression was measured using 9-item Patient Health Questionnaire (PHQ-9) [30], a Likert questionnaire composed of 9 items.Participants were asked about the frequency of depressive symptoms in the past 2 weeks.Every item ranged from 1 (not at all) to 4 (almost every day).
The higher the sum score, the severer the participant's depression degree.With reference to advanced research [30], scoring above 13 was considered as existed depression.The Chinese version of PHQ-9 questionnaire had a good reliability and validity among college students [31] .(Cronbach'salpha=0.871;range 9-36) Loneliness.The 8-item UCLA loneliness Scale was used to evaluate loneliness among participants [32].
There are 8 items in the Likert questionnaire, ranging from 1 (not at all) to 4 (almost every day).The items were concentrated on participants' subjective feeling of loneliness.A higher total score corresponded to higher level of loneliness.Since no standard cut-off point was available, the upper quartile (T0), 17, was set as the cut-off point.Participants with ULS-8 scores higher than 17 were de ned as relatively high level of perceived loneliness at the time of investigation.(Cronbach's alpha=0.829;range 8-29) Defeat.Defeat Scale was used to assess participants' feeling of being defeated [28], which is a questionnaire of 16 items, with every item ranging from 0 (never) to 4 (always).The Chinese vision of Defeat Scale was proved valid and reliable in Chinese medical students [33].A higher total score indicated a severer feeling of defeat of the participant.The upper quartile (T0) 18 was used as the cut-off point.Participants with defeat scores higher than 18 were de ned as relatively high level of perceived defeat at the time of investigation.(Cronbach's alpha=0.907;range 0-52) Social support.Multiple Scales of Perceived Social Support was used for measurement of participants' social support.MSPSS is composed of 12 questions about participants' subjective feelings of support from family, friends and others.The MSPSS has been widely used in multiple countries, which showed good reliability and validity [34,35].The higher total score meant more social support, hence the lower quartile (T0), 67, was picked as the cut-off point.Participants with MSPSS scores lower than 67 were de ned as relatively low level of perceived social support at the time of investigation.(Cronbach's alpha=0.960;range 33-84) Interpersonal needs.The 15-item Interpersonal Needs Questionnaire scale included six questions to measure perceived burdensomeness and nine questions to assess thwarted belongingness[36], ranging from 1 (strongly disagree) to 7 (strongly agree).With 6 of the items were reverse-scored, a higher sum score meant higher status of TB and PB of the participant.The upper quartile (T0), 37, was set as the cutoff point.Participants with INQ-15 scores higher than 37 were de ned as relatively high level of unmet interpersonal needs at the time of investigation.The Chinese version of the questionnaire had good reliability and validity among Chinese college students [37].(Cronbach's alpha=0.895;range 15-78).

Outcome
First-onset suicidal ideation.Suicidal ideation was measured by asking students: "Have you ever had thoughts of taking your own life?" (T0) and "During the past 12 months have you had thoughts of taking your own life?" (T1) [38].A "yes" for the rst question was valued as existed lifetime suicidal ideation.And a "yes" for the latter question was regarded as having suicidal ideation during 12 months.Thus, rstonset suicidal ideation was de ned as absent suicidal ideation at T0 but present at T1.

Statistical analysis
In order to estimate the association between entrapment and rst-onset suicidal ideation, all 211 samples were divided into 4 subgroups according to their exposure to entrapment.All the covariates except for entrapment were collected at the same time when the outcome was measured (T0).Statistical Package for Social Sciences (version 26.0 for Windows; IBM SPSS Statistics, Armonk, NY, USA) was used for descriptive analysis and logistic regression.Several logistic regression models were conducted afterwards to examine difference between the subgroups.Statistical signi cance was claimed for p<0.05.
6.16% of the participants (16/211) reported occurring suicidal ideation in the past year.Among all variables measured at baseline, only depression and loneliness showed signi cant relationship with rstonset suicidal ideation (OR=4.431,5.943).

Suicidal Ideation Of Subgroups
Table 2 displayed that 6.16% of the total participants (13/211) reported suicidal ideation in past one year.
There were signi cant differences of suicidal ideation prevalence among 4 subgroups (χ 2 = 16.269,p=0.001) that those who newly onset perceived entrapment at T1 had the highest prevalence (18.92%, 7/37).There was no signi cant difference of socio-demographic characteristics among 4 subgroups except for gender.

Discussion
prevalence of rst-onset suicidal ideation among medical students in their second year of school were reported at the rate of 6.16% in our study, lower than that of the crude summary prevalence of 11.1% among medical students during medical school [39].
The enlightening part of our study is the robust predictor of rst-onset suicidal ideation, new-onset entrapment.In line with our result, multiple studies and models agreed to demonstrate the leading signi cance of entrapment in the formation of suicidal ideation [22,40], but were divided by diversi ed study designs in regard to subjects, psychological variables and so on [20,25,41,42].Most of the previous studies are cross-sectional studies, while there are several longitudinal researches attempting to achieve real-time observation of subjects' the variability of certain psychological factors by assessing them multiple times per day [25,43,44].While limited long-term longitudinal researches on this topic has been done before, our study is the rst one with a follow-up period as long as one year.With comparison to existing researches, the most innovative point of this longitudinal survey is to divide the level of exposure to entrapment into 4 classi cations so as to explore the relevance between different stages of entrapment and suicidal ideation conversion.Our research demonstrates the close relation between entrapment, especially new-onset entrapment with rst-onset suicidal ideation, which supports the IMV model, corroborating that entrapment is an essential predictor of rst-onset suicidal ideation.
New-onset entrapment is mostly related to suicidal ideation, possibly because the participants who perceived new-onset entrapment had been in a situation of external or internal pressure shortly and may encounter a stronger subjective feeling of no way to ee and desperation, while participants who were positive in persistent entrapment are more inclined to get used to the dilemma they met, which may lower the chance to think about extreme solutions such as suicide.In accord with IMV model, the protective motivational moderators may have not taken shape in comparison to the perception persistent entrapment, which may have developed tolerance to entrapment.There is no valid basis of this assumption yet, thus further studies are needed to verify the relevance of new-onset entrapment and persistent entrapment with suicidal ideation conversion.
There are several limitations in our current research that should be taken into account.Firstly, as a longitudinal study with a follow-up period of 12 months, loss of follow-up appears to be a problem.Only 32.16% (211/656) of the eligible freshmen completed the follow-up survey.Secondly, the sample is restricted to the freshmen of one medical school, subsequently leading to a relatively small sample size, which may contribute to sampling error.However, the relatively small sample size guaranteed a more reliable follow-up.Thirdly, the evaluation tool for suicidal ideation used in this study is a set of simpli ed questions which was originated from previous studies.If we could use scale evaluating not only suicidal ideation but also suicide behaviors, there may be more deep-going ndings.Ultimately, according to the study, entrapment possibly work as a mediator in the whole course of development of suicidal ideation, therefore, further research targeting the pathway is required in order to explore the generating process of suicidal ideation and intervention.

Conclusions
Since entrapment has been corroborated to be uctuating, regular follow-up of the level of entrapment could be an effective measure of screening and preventing suicidal ideation conversion given its signi cance in suicidal ideation conversion.With reference to IMV model, whoever is found to have a perception of entrapment, especially new-onset entrapment, should be more concerned and guarded against motivational moderators such as thwarted belongingness, burdensomeness, lack of future thoughts, lack of social support, negative attitudes.To sum up, more attention should be attached to newonset entrapment when it comes to suicidal ideation intervention. Abbreviations

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Table 1
Socio-demographic and psychological variables associated with suicidal ideation.

Table 2
Subgroup division and suicidal ideation within 4 subgroups.

Table 3
Different models of entrapment exposure with risk of suicidal ideation conversion.ORm: multivariate odds ratio of Model 3 included entrapment and all other variables measured at T0(gender, age, parents' income, academic performance, defeat, loneliness, depression, interpersonal needs and social support). c