title: Risk factors and study designs used in research of youths' suicide behaviour-an epidemiological discussion with focus on level of evidence.
abstract: Abstract Introduction: Many different epidemiology study designs have been used to analyse risk factors for suicide behaviour. The purpose of this study was to obtain an insight into the current study design used in research on youths' risk factors for suicide behaviour and to rank the studies according to level of evidence (LoE).
  
  
  METHODS
  We searched PubMed and psycINFO in order to identify relevant individual studies.
  
  
  RESULTS
  We included 36 studies of children and youth on suicidal behaviour and ideation-many rank low on LoE. For suicide, cohort design was often used, and mental illness (depression, substance abuse and severity of mental illness) was the most common risk factor. Cohort studies are ranked 2b, which is high according to LoE. For suicide attempts, survey was often used, and psychopathology, substance abuse and being exposed to suicidal behaviour were the most common risk factors. For suicidal ideation, survey was the only design used, and substance abuse and psychopathology the most common risk factors. Surveys are ranked 4, which are low according to LoE. Many risk factors were broad and unspecific, and standard definitions of outcome and exposure were rarely used.
  
  
  CONCLUSIONS
  A good study of risk factors for suicidal behaviour would need a high LoE, as a high-powered longitudinal epidemiological study (cohort or case-control) of very specific risk factors. The factors would have high prevention potential, compared with more broad and unspecific risk factors, to which many people are exposed. We would recommend a cohort design (in high-risk populations) or a case-control design to identify risk factors, using clinical and/or register data instead of self-reported information, reporting adjusted estimates and using standard definition of suicidal outcome and risk factors.
authors.affiliation: Erik Christiansen, M.Sc., Child and Adolescent Psychiatric Department and Institute of Regional Health Services Research, University of Southern Denmark , Odense , Denmark.
authors.forename: Erik
authors.initials: E
authors.lastname: Christiansen
authors.forename: Kim Juul
authors.initials: KJ
authors.lastname: Larsen
authors.forename: Esben
authors.initials: E
authors.lastname: Agerbo
authors.forename: Niels
authors.initials: N
authors.lastname: Bilenberg
authors.forename: Elsebeth
authors.initials: E
authors.lastname: Stenager
mesh_terms: D000293:Adolescent; D002648:Child; D006801:Humans; D012107:Research Design / Q000706:statistics & numerical data*; D012307:Risk Factors; D013405:Suicide / Q000706:statistics & numerical data*
keywords: Children and adolescents; Epidemiology; Risk factors; Study design; Suicide behaviour