Discuss research into the contribution of genetic and neurological factors to depression.

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Discuss research into the contribution of genetic and neurological factors to depression

There is not much evidence for genetic factors in unipolar depression, but there is quite strong evidence in bipolar.  

Family history studies indicate that first-degree biological relatives (parents, siblings and children) of those with severe psychotic depression have a morbidity risk of between 4-24%, whereas the risk in the general population is 1-2%.  However the problem with family studies is that they share the same environment and the nature-nurture debate comes into play.

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Twin studies provide more convincing evidence.  Price looked at seven twin studies and found much higher concordance rates for manic-depressives in MZ twins than DZ ones.  The most revealing factor was that the concordance rate for MZ twins raised together and raised the apart was almost the same.

Adoption studies have also provided genetic evidence.  In a study by Cadoret 126 adopted children, 8 of which had a manic-depressive biological parent, but health adopted parents were observed.  Three out of the eight later developed a major affective disorder, compared to only eight of the remaining 118 ...

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