Kaji’s alcohol study

• Kaij's twin study of alcohol abuse

  1960 Swedish study looking for concordance in alcohol abuse
• Concordance rate


  The likelihood of two people sharing a characteristic
• The higher the concordance rate in identical twins than fraternal twins


  The more likely that characteristic is to be genetic in nature
• Kaij's study


  • Used a large sample size
  • Showed a large effect
• Kaij's study provides strong statistical evidence for the existence of a genetic vulnerability to alcohol addiction
• Practical application


  Understanding that addiction may be in part inherited can lead doctors to offer help to other family members who may be suffering
• Kaij's study only investigated alcohol addiction, it may be there is only a genetic vulnerability to alcohol addiction so these results may not be generalisable to other substance addictions
• Kaij's study showed a strong concordance rate, however 46% of identical twins were not concordant, 100% would be expected for a fully genetic characteristic
• There is evidence for both genetic and environmental effects influencing alcohol addiction


  This supports a diathesis stress explanation, genes cause a vulnerability but need to be triggered by environmental factors