Genetic explanation


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  • I was disappointed to see that someone (susannahwebb) has taken a powerpoint that I took a lot of time to produce, edited the first few slides a little, then put it on Slideshare as her own. This was put on Psychexchange for sharing with colleagues, not to have it taken by someone else and presented as their own. Forgive my bruised ego here, but this is definitely out of order!
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Genetic explanation

  1. 1. Genetic explanation Family, twin and adoption Biological studies explanations of Depression
  2. 2. Mood Disorders – Genetic• Depression tends to run in families• The closer the relationship with a sufferer, the more likely a person will have a mood disorder• Genetic evidence is strongest for most severe forms of the disorder• Concordance rates also indicate a substantial environmental contribution
  3. 3. Mood Disorders – Genetic• Zubenko et al (2001) – Family history – 50% of FD relatives, 25% of SD relatives also had mood disorder – Relatives had increased risk of suicide & liver disease
  4. 4. Genetics & Depression Qu. How do you ‘prove’ a genetic argument for any behaviour? Twin studies: Allen, 1976 Bertelsen 1977MZ 40% 59% Qu. Problems?DZ 11% 30%
  5. 5. Genetics & Depression Family concordance rates Gershon 1990 Wender 1986Gen Pop 15% 15%Family 40-50% 70% if adopted Qu. Problems?
  6. 6. Genetic explanation DEPRESSION RESEARCHERFamily studies “In 1990, I reviewed many family studies … … in each study, depression was assessed in the first degree relatives of patients with depression …Gershon “I showed that depression rates in these first degree relatives was about two to three times the rate in the general population … “My work was supported by Sullivan et al (2000), who showed similar findings in a review of several family studies…
  7. 7. Genetic explanation McGuffin 1996Twin studies “In twin studies, we look at CONCORDANCE RATES for depression in MZ and DZ twins … “If depression isMZ twins have identical genes! caused by a gene,If depression is caused bygenes, then if they have the we would expectgene they should BOTH have that MZ twinsdepression! either BOTH have depression, or “So we would NEITHER have expect to find a depression … DZ twins share 50% of their genes! HIGHER CONCORDANCE So one twin could have the gene for depression, while the for depression in other doesn’t! MZ twins than in DZ twins …
  8. 8. Genetic explanation McGuffinTwin studies “Here are the twin study research findings … “In 1976, Allen reviewed MZ/DZ studies and found aMZ: either both have the genefor depression, or neither mean concordancedoes – so should be concordant rate of 40% for MZ twins, and just 11% for DZ twins … “In 1977, Bertelson et al found a “In 1996, my team DZ: might both have the gene, concordance of 59% and I found 46% both not have the gene, or one for MZ twins, and concordance for could have the gene and one 30% for DZ twins … might not have it! This means depression in MZ we expect a lower concordance twins, and just 20% for depression in DZ twins, in DZ twins … than we do in MZ twins
  9. 9. Genetic explanation McGuffinTwin studies “I’ll summarise the findings for you … TWIN STUDIES … Allen (1976) MZ 40% DZ 11%CONCORDANT FOR DEPRESSION? Bertelson (1977) MZ 59% DZ 30% McGuffin (1996) MZ 46% DZ 20% “Do these data support the idea that “Thinking about what CONCORDANT FOR DEPRESSION? depression is caused you understand by genes? … about genes and MZ/DZ twins, can you criticise these findings? …
  10. 10. Genetic explanation WenderAdoption studies “I looked at adoption studies, because when a child is adopted, it is taken away from its home and family environment … “Family studies like Gershon’s, and twin studies like McGuffin’s, can’t say genes are the only reason for What causes depression depression, because they didn’t separate genes from environment … “Adoption studies are an improvement, because they eliminate the influence of the family environment …
  11. 11. Genetic explanation Wender “I published two Adoption studies sets of findings in 1986 … We found that biological relatives of adopted sufferers of depression were SEVEN TIMES more likely than adoptive relatives to have had depression themselves! “Both sets of findings suggest When we looked at adopted children who that genetics play later developed depression, we found that a big part in their biological parents were EIGHT depression … TIMES more likely than their adoptive parents, to have suffered from depression And we’re happy I’m feeling So am I … … so why is our prickly but I don’t adopted lad today… know why! depressed??? We’re both okay! What a nice day! Parents with Parent withBiological parent adopted child biological child