title: A population-based Swedish Twin and Sibling Study of cannabis, stimulant and sedative abuse in men.
abstract: BACKGROUND
  Prior studies, utilizing interview-based assessments, suggest that most of the genetic risk factors for drug abuse (DA) are non-specific with a minority acting specifically on risk for abuse of particular psychoactive substance classes. We seek to replicate these findings using objective national registry data.
  
  
  METHODS
  We examined abuse of cannabis, stimulants (including cocaine) and sedatives ascertained from national Swedish registers in male-male monozygotic (1720 pairs) and dizygotic twins (1219 pairs) combined with near-age full siblings (76,457 pairs) to provide sufficient power. Modeling was performed using Mx.
  
  
  RESULTS
  A common pathway model fitted better than an independent pathway model. The latent liability to DA was highly heritable but also influenced by shared environment. Cannabis, stimulant and sedative abuse all loaded strongly on the common factor. Estimates for the total heritability for the three forms of substance abuse ranged from 64 to 70%. Between 75 and 90% of that genetic risk was non-specific, coming from the common factor with the remainder deriving from substance specific genetic risk factors. By contrast, all of the shared environmental effects, which accounted for 18-20% of the variance in liability, were non-specific.
  
  
  CONCLUSIONS
  In accord with prior studies based on personal interviews, the large preponderance of genetic risk factors for abuse of specific classes of psychoactive substance are non-specific. These results suggest that genetic variation in the primary sites of action of the psychoactive drugs, which differ widely across most drug classes, play a minor role in human individual differences in risk for DA.
authors: Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, VA, USA; Department of Psychiatry, Virginia Commonwealth University, Richmond, VA, USA; Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, VA, USA. Electronic address: kendler@vcu.edu.
authors: Kenneth S
authors: KS
authors: Kendler
authors: Center for Primary Health Care Research, Lund University, Malmö, Sweden.
authors: Henrik
authors: H
authors: Ohlsson
authors: Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, VA, USA; Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, VA, USA; Massey Cancer Center, Virginia Commonwealth University, Richmond, VA, USA.
authors: Hermine H
authors: HH
authors: Maes
authors: Center for Primary Health Care Research, Lund University, Malmö, Sweden; Stanford Prevention Research Center, Stanford University School of Medicine, Stanford, CA, USA.
authors: Kristina
authors: K
authors: Sundquist
authors: Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Stockholm, Sweden.
authors: Paul
authors: P
authors: Lichtenstein
authors: Center for Primary Health Care Research, Lund University, Malmö, Sweden; Stanford Prevention Research Center, Stanford University School of Medicine, Stanford, CA, USA.
authors: Jan
authors: J
authors: Sundquist
mesh_terms: D000328:Adult; D000697:Central Nervous System Stimulants; D003042:Cocaine; D020022:Genetic Predisposition to Disease; D006801:Humans; D006993:Hypnotics and Sedatives; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology / Q000235:genetics* / Q000523:psychology; D015233:Models, Statistical; D012042:Registries; D012307:Risk Factors; D035781:Siblings; D019966:Substance-Related Disorders / Q000453:epidemiology / Q000235:genetics* / Q000523:psychology; D013548:Sweden / Q000453:epidemiology; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic
chemical_list: D000697:Central Nervous System Stimulants; D006993:Hypnotics and Sedatives; D003042:Cocaine
keywords: Cannabis; Drug abuse; Genetics; Sedatives; Stimulants; Twins