2.1 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 first 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, 12-month follow-up cohort was established(N=211) (see Fig.1).
Inclusion criteria:(1) undergraduates enrolled in 2017 for the first time, (2) proficiency in Chinese.
2.2 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.
2.3 Measures
2.3.1 Socio-demographic variables
Socio-demographic variables included gender (‘male’ and ‘female’), major (‘Clinical medicine’ and ‘non-clinical medicine’), parents’ income (‘High’, ‘Average’ vs ‘Low’), and academic performance (‘good (the first third in class)’, ‘average’ or ‘Poor (the last third in class)’) were measured at the baseline survey.
2.3.2 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 defined 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’s alpha=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 defined 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 defined 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 defined 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 cut-off point. Participants with INQ-15 scores higher than 37 were defined 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).
2.3.3 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 first 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, first-onset suicidal ideation was defined as absent suicidal ideation at T0 but present at T1.
2.5 Statistical analysis
In order to estimate the association between entrapment and first-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 significance was claimed for p<0.05.