title: Attention-deficit/hyperactivity disorder and risk for drug use disorder: a population-based follow-up and co-relative study.
abstract: BACKGROUND
  Although the association between attention-deficit/hyperactivity disorder (ADHD) and drug use disorder (DUD) is well documented, it is unclear whether it is causal or results from familial confounding.
  
  
  METHODS
  In this study we included all 551 164 individuals born in Sweden between 1991 and 1995 and used linked data from multiple nationwide registries to identify those with ADHD prior to age 15 years (1.71%). We used Cox proportional hazards models to investigate the future risk for DUD as a function of an ADHD registration and then compared the results from the entire population with the results from a co-relative design. Using the Swedish Multi-Generation Register, we identified all full-sibling, half-sibling and first-cousin pairs discordant for ADHD.
  
  
  RESULTS
  In the population sample, ADHD had a substantially increased risk for future DUD with a hazard ratio (HR) of 3.34 after accounting for gender and parental education. Examining discordant cousin pairs, discordant half-siblings and discordant siblings, those with ADHD had HRs for DUD of 3.09, 2.10 and 2.38 respectively. Controlling for the number of ADHD registrations, ADHD patients with and without stimulant treatment were similarly associated with later DUD risk.
  
  
  CONCLUSIONS
  ADHD diagnosed before 15 years of age was strongly related to future risk for DUD. The magnitude of this association was modestly reduced in relative pairs discordant for ADHD, suggesting that the ADHD-DUD association is partly causal and partly a result of familial confounding. We found no evidence to suggest that this association resulted from stimulant treatment.
authors.affiliation: Center for Primary Health Care Research,Lund University,Malmö,Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Sundquist
authors.affiliation: Center for Primary Health Care Research,Lund University,Malmö,Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Ohlsson
authors.affiliation: Center for Primary Health Care Research,Lund University,Malmö,Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Sundquist
authors.affiliation: Virginia Institute for Psychiatric and Behavioral Genetics,Virginia Commonwealth University,Richmond, VA,USA.
authors.forename: K S
authors.initials: KS
authors.lastname: Kendler
mesh_terms: D000293:Adolescent; D000328:Adult; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology* / Q000235:genetics; D015984:Causality; D015331:Cohort Studies; D005190:Family; D005260:Female; D006801:Humans; D008297:Male; D016016:Proportional Hazards Models; D012042:Registries; D012307:Risk Factors; D035781:Siblings; D019966:Substance-Related Disorders / Q000453:epidemiology* / Q000235:genetics; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult
keywords: Swedish national cohort