The aim of this study was to investigate the risk factors for suicidal ideation in adolescents by gender and age. This study used 2013 nationwide school-based mental health screening test data from 591,303 seventh grade students and 618,271 tenth grade students in Korea. Suicidal ideation, four psychological problems, and three adverse life events were evaluated using the Adolescents Mental Health and Problem Behavior Screening Questionnaire-II. Of all students, 12.9-14.7% of the boys and 17.1-23.2% of the girls had suicidal ideation. Mood had the greatest impact on the risk for suicidal ideation and other factors also significantly increased the risk of suicidal ideation. Distractibility was positively related to suicidal ideation only in seventh grade students and behavioral problems increased suicidal ideation more in girls than in boys. Violence constituted the most powerful factor for suicidal ideation among the events; however, bullying constituted the most important event that increased suicidal ideation in seventh grade girls. All factors except 'Distractibility' increased the risk of severe suicidal ideation. The risk factors for suicidal ideation in adolescents differed by gender and age. Interventions should be made according to these characteristics to reduce suicidal ideation in adolescents.

BackgroundWe investigated the characteristics of adolescents who committed suicide in South Korea, and how these characteristics differed by gender.MethodData from middle and high school students who committed suicide between 2014 and 2016 were analyzed. We evaluated differences in suicide method and place, personal characteristics, and school life characteristics by gender using the Chi square test and t test.ResultsJumping from a high place was the most common suicide method for both male and female students. A significantly greater proportion of female adolescents had experienced depressive symptoms, previous self-injury, previous suicide attempts, and had problems with school attendance and peers. Additionally, they were more likely to be classified as high risk according to a school-based mental health screening test and to utilize professional mental health treatment services.ConclusionOur results demonstrate that adolescents who committed suicide exhibited gender differences in personal characteristics and school life. These characteristics might aid in the development of adolescent suicide policies and intervention programs.Electronic supplementary materialThe online version of this article (10.1186/s13034-019-0274-3) contains supplementary material, which is available to authorized users.

Abstract. Background: Youth suicides have diverse characteristics according to the young people's developmental stages. Warning signs and communication of suicidal intent can be vague among early adolescents, while mental health problems may be more evidently related to suicidal ideation in older adolescents. Understanding the developmental characteristics of youth suicide is necessary for effective suicide prevention. Aims: We explored the differences between children and adolescents who died by suicide and the characteristics of these young people as observed by their school teachers. Method: We analyzed teachers' mandatory postmortem reports of suicides among 308 Korean students. We compared: suicide-related information including personal, familial, and school factors; stressful life events; and participation in interventions among elementary, middle, and high school students who died by suicide. We also assessed the distribution of student suicides per month. Results: Suicide among elementary school students increased during school vacations, and suicide among middle and high school students increased during the school semester. According to the teachers' reports, elementary school students who died by suicide were more extroverted and had better academic achievements than their high school peers, and had significantly lower levels of substance/tobacco use. Elementary school students who died by suicide showed significantly less academic stress and use of external professional help than did other groups. Limitations: Because this research is based on mandatory teacher reports, the subjective opinions of teachers may have affected the reliability of the data. Suicide by out-of-school youth was not included. Conclusion: School-based suicide prevention should be implemented in accordance with young people's developmental characteristics.

The present findings suggest that adolescents with suicidal ideation can be classified into several distinct subtypes based on mental health problems. These profiles and their associated covariates will aid in the establishment of youth suicide prevention policies.

Lithology is an important control on the efficiency of bedrock incision and thus the pace of landscape evolution. Rock strength is commonly considered the limiting lithologic factor that resists erosion. Yet, rock strength is a dynamic property that oscillates during advection of rock to the channel surface as damaging processes weaken rock and erosion exposes fresh rock. We approach the problem by investigating damage on bedrock surfaces that vary by the frequency they are eroded in channels of different lithologies. Our data set includes measurements of channel slope and width to characterize channel morphology, and Schmidt hammer rebound, P wave velocity, slake durability, and porosity to characterize the mechanical properties of channel surfaces. The average damage accumulation rate of lithologies ranges over 41% of the mean. We find a range of damage patterns among the different lithologies. Local surface damage increases with erosion frequency in channels comprised of coarse‐grained bedrock but decreases with erosion frequency in channels comprised of fine‐grained bedrock. We interpret these patterns to develop from lithological influences on weathering, abrasion, and the threshold of damage to erosion. The cross‐channel damage patterns between channel floors and margins are well correlated with stream power demonstrating links between microstructural rock properties, reach‐scale morphology, and landscape‐scale processes. We conclude that the morphodynamics of bedrock channels are sensitive to the lithological influences on the direction and magnitude of feedback in the coevolution of bedform morphology and the mechanical properties of the surface.