Kaij's Twin Study

• Aim

  To see if addiction is due to hereditary factors, using twins
• Method

  Male twins with at least one twin registered to the temperance board for alcohol problems were interviewed, along with their family members
• Results


  61% of identical (MZ) twins and 39% of non-identical (DZ) twins were both alcoholic
• Conclusion 


  Addiction is related to genetic vulnerability

  The data supports this as if genetics had no part to play we would expect the data for identical (MZ) and non-identical (DZ) twins to be the same, but it also isn't 100% genetic as if it was all identical (MZ) twins would be alcoholics
• Weakness


  The temperance board only includes drinkers who made a public display of their drinking - so doesn't include all alcoholics
• Strength


  Supporting research from later studies shows that identical (MZ) twins were more likely to both be alcoholics than non-identical (DZ) twins