Kendler (2006)

Question 1

Aim

Answer 1

To investigate whether there significant gender differences in the heritability of major depression

To investigate whether there evidence that genetic and environmental factors in major depression differ over time

Question 2

Participants

Answer 2

15,493 complete twin pairs listed in the national Swedish Twin Registry

Question 3

Method

Answer 3

• Telephone interviews conducted to assess participants for lifetime major depression by using modified DSM-IV criteria. 8056 twins met the criteria for a diagnosis of major depression at some point in their life - and 322 twins voluntarily discussed a history of antidepressant treatment
• Interviewers also asked questions about the twins “shared environment” and “individual specific environment”

Question 4

Results

Answer 4

• Concordance rates for major depression were significantly higher in women than men
• Correlations were significantly higher in monozygotic than in dizygotic twins
• No correlation between the number of years that the twins had lived together and lifetime major depression

Question 5

Conclusion

Answer 5

• Both that the heritability of major depression is higher in women than in men and that some genetic risk factors for major depression are sex-specific
• Confirms the level of heritability of major depression found in other studies