title: Early onset alcohol use and self-harm: a discordant twin analysis.
abstract: BACKGROUND
  Self-harm has considerable societal and economic costs and has been extensively studied in relation to alcohol involvement. Although early onset alcohol use (EAU) has been causally linked to maladaptive clinical outcomes, its association with self-harm is less well characterized. This study aimed to further examine the link between EAU and both nonsuicidal self-injury (NSSI) and suicide attempt (SA), and elucidate shared familial and causal/individual-specific pathways that explain this co-occurrence.
  
  
  METHODS
  Using data from 6,082 Australian same-sex twin pairs (1,732 monozygotic [MZ] and 1,309 dizygotic [DZ]), ages 23 to 40, we examined prevalence rates of NSSI and SA among twin pairs concordant and discordant for EAU. Conditional logistic regression, controlling for early clinical covariates and the influence of zygosity on EAU, was used to examine the odds ratio (OR) of self-harm within twin pairs discordant for EAU.
  
  
  RESULTS
  Prevalence rates of both NSSI and SA were highest among twin pairs concordant for EAU and for twins who reported EAU within discordant twin pairs. Results from discordant twin analyses revealed nearly 4-fold increased odds of SA for the twin who endorsed EAU, and this OR was equal across MZ and DZ twins. EAU also was associated with elevated odds of NSSI (OR = 7.62), although this was only the case for DZ twins in discordant pairs.
  
  
  CONCLUSIONS
  The equivalent increase in odds of SA for both MZ and DZ twins suggests that causal or individual-specific influences explain the link between EAU and SA. For NSSI, elevated odds for DZ twins and nonsignificant findings for MZ twins implicate correlated genetic factors in the association between EAU and NSSI. Future studies should test mechanisms through which EAU may causally influence SA, as well as examine whether genetic risk for third variables (e.g., negative urgency, stress reactivity) may explain the genetic overlap between EAU and NSSI.
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, Saint Louis, Missouri.
authors.forename: Lauren R
authors.initials: LR
authors.lastname: Few
authors.affiliation: George Warren Brown School of Social Work, Washington University, Saint Louis, Missouri.
authors.forename: Kimberly B
authors.initials: KB
authors.lastname: Werner
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, Saint Louis, Missouri.|Department of Psychiatry, Yale University School of Medicine, West Haven, Connecticut.
authors.forename: Carolyn E
authors.initials: CE
authors.lastname: Sartor
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, Saint Louis, Missouri.
authors.forename: Julia D
authors.initials: JD
authors.lastname: Grant
authors.affiliation: Department of Psychological Sciences, University of Missouri, Columbia, Missouri.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Trull
authors.affiliation: Department of Psychology, Harvard University, Cambridge, Massachusetts.
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Nock
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, Saint Louis, Missouri.
authors.forename: Kathleen K
authors.initials: KK
authors.lastname: Bucholz
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, Saint Louis, Missouri.
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Deitz
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, Saint Louis, Missouri.
authors.forename: Anne L
authors.initials: AL
authors.lastname: Glowinski
authors.affiliation: QIMR Medical Research Institute, Brisbane, Queensland, Australia.
authors.forename: Nicholas G
authors.initials: NG
authors.lastname: Martin
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, Saint Louis, Missouri.
authors.forename: Elliot C
authors.initials: EC
authors.lastname: Nelson
authors.affiliation: School of Social Sciences, University of the Sunshine Coast, Sippy Downs, Queensland, Australia.
authors.forename: Dixie J
authors.initials: DJ
authors.lastname: Statham
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, Saint Louis, Missouri.
authors.forename: Pamela A F
authors.initials: PA
authors.lastname: Madden
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, Saint Louis, Missouri.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Heath
authors.affiliation: Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Lynskey
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, Saint Louis, Missouri.
authors.forename: Arpana
authors.initials: A
authors.lastname: Agrawal
mesh_terms: D000328:Adult; D000367:Age Factors; D000428:Alcohol Drinking / Q000009:adverse effects / Q000453:epidemiology* / Q000235:genetics; D001315:Australia / Q000453:epidemiology; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D012307:Risk Factors; D012309:Risk-Taking; D016728:Self-Injurious Behavior / Q000453:epidemiology* / Q000235:genetics; D014429:Twins, Dizygotic / Q000235:genetics; D014430:Twins, Monozygotic / Q000235:genetics; D055815:Young Adult
keywords: Early Alcohol Use; Self-Harm