title: Time trends in symptoms of mental illness in children and adolescents in Canada.
abstract: BACKGROUND
  Existing research and media reports convey conflicting impressions of trends in the prevalence of mental illness. We sought to investigate trends in the prevalence of symptoms of mental illness in a large population-based cohort of Canadian children and adolescents.
  
  
  METHODS
  We obtained population-based data from the National Longitudinal Survey of Children and Youth. Every 2 years, participants completed self-reported measures of mental illness indicators, including conduct disorder, hyperactivity, indirect aggression, suicidal behaviour, and depression and anxiety. We analyzed trends in mean scores over time using linear regression.
  
  
  RESULTS
  We evaluated 11 725 participants aged 10-11 years from cycles 1 (1994/95) through 6 (2004/05), 10 574 aged 12-13 years from cycles 2 (1996/97) through 7 (2006/07), and 9835 aged 14-15 years from cycles 3 (1998/99) through 8 (2008/09). The distribution of scores on depression and anxiety, conduct and indirect aggression scales remained stable or showed small decreases over time for participants of all ages. The mean hyperactivity score increased over time in participants aged 10-11 years (change per 2-year cycle: 0.16, 95% CI 0.02 to 0.12) and those aged 12-13 years (0.13, 95% CI 0.09 to 0.18). Over time, fewer participants aged 12-13 years (0.40% per cycle, 95% CI -0.78 to -0.07) and aged 14-15 years (0.56% per cycle, 95% CI -0.91 to -0.23) reported attempting suicide in the previous 12 months.
  
  
  CONCLUSIONS
  With the exception of hyperactivity, the prevalence of symptoms of mental illness in Canadian children and adolescents has remained relatively stable from 1994/95 to 2008/09. Conflicting reports of escalating rates of mental illness in Canada may be explained by differing methodologies between studies, an increase in treatment-seeking behaviour, or changes in diagnostic criteria or practices.
authors.affiliation: Department of Epidemiology and Community Medicine, University of Ottawa, Ottawa, Ont.
authors.forename: Seanna E
authors.initials: SE
authors.lastname: McMartin
authors.affiliation: Department of Epidemiology and Community Medicine, University of Ottawa, Ottawa, Ont.
authors.forename: Mila
authors.initials: M
authors.lastname: Kingsbury
authors.affiliation: Department of Epidemiology and Community Medicine, University of Ottawa, Ottawa, Ont.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Dykxhoorn
authors.affiliation: Department of Epidemiology and Community Medicine, University of Ottawa, Ottawa, Ont. icolman@uottawa.ca.
authors.forename: Ian
authors.initials: I
authors.lastname: Colman
mesh_terms: D000293:Adolescent; D002170:Canada / Q000453:epidemiology; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000175:diagnosis* / Q000453:epidemiology*; D011446:Prospective Studies; D063189:Symptom Assessment; D013997:Time Factors