title: IQ in early adulthood and later risk of death by homicide: cohort study of 1 million men.
abstract: BACKGROUND
  Risk factors for homicide are emerging; however, the predictive value of IQ, for which there is a strong prima facie case, has yet to be examined.
  
  
  OBJECTIVE
  To examine the association between IQ and risk of death by homicide.
  
  
  METHODS
  A cohort of 968 846 men, aged 18-19 years, were administered an IQ test battery at military conscription and then followed for mortality experience over two decades.
  
  
  RESULTS
  There were 191 deaths due to homicide during follow-up. In age-adjusted analyses, a high total IQ test score was associated with a reduced rate of homicide (hazard ratio (HR) per standard deviation increase in IQ score=0.49, 95% CI 0.42-0.57). A step-wise gradient was apparent across the three IQ groups (P-value for trend <0.001). After adjustment for indicators of socio-economic position and illness at conscription, this gradient was marginally attenuated (HR=0.57, 95% CI 0.49-0.67).
  
  
  CONCLUSIONS
  High IQ test scores in early adulthood were associated with a reduced risk of death by homicide.
authors.affiliation: MRC Social & Public Health Sciences Unit, University of Glasgow, Glasgow, UK.
authors.forename: G David
authors.initials: GD
authors.lastname: Batty
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Deary
authors.forename: Anders
authors.initials: A
authors.lastname: Tengstrom
authors.forename: Finn
authors.initials: F
authors.lastname: Rasmussen
mesh_terms: D000293:Adolescent; D016021:Epidemiologic Studies; D006306:Health Surveys; D006708:Homicide / Q000523:psychology / Q000706:statistics & numerical data*; D006801:Humans; D007360:Intelligence; D007361:Intelligence Tests; D008297:Male; D008889:Military Personnel / Q000523:psychology*; D013548:Sweden; D055815:Young Adult