Adoption Stydies

Question 1

Adoption studies and schizophrenia

Plomin 1997

Answer 1

Several of the adopted away children with schizophrenic mothers suffered from schizophrenia themselves. While those with non schizophrenic parents did not show any signs.

This supports the theory that schizophrenia is a biological rather than environmental specific.

Question 2

Antisocial personality disorder

Roth and Finley 1998

Answer 2

Antisocial personality disorder is more likely to present its self in adoptees that already have a biological risk (at least one parent has a history of antisocial or criminal behaviour)

Results ~ the adoptees that are born with no risk of developing the disorder do usually develop it while living in an adaptive environment.

Question 3

Adoption studies Limitations & Benefits

Answer 3

The number of adoptees (less frequent as contraception and abortion increase, unmarried mothers keep their babies).

Representativeness ~ not representative of others

Prenatal environment ~resemblance between birth mothers prenatal environment, may reflect prenatal environmental influences.
…… However, prenatal effects can be tested independently from post natal environments by comparing correlation from birth mothers and fathers.

Difficult to study birth fathers
…. Compare biological half siblings related to the mother and the father. For paternal half siblings, show the same risks for schizophrenia as maternal half siblings do, suggesting that prenatal factors may be of great importance.

Selective placement could cloud the separation of nature and nurture by placing adopted apart relatives into correlated environments.

Question 4

Family Studies

Bipolar and Schizophrenia

Berrettini 2000

Answer 4

First degree relatives of people suffered from both bipolar and schizophrenia experienced higher risk of schizoaffective and recurrent unipolar disorders.

This indicates an overlap in family risk for bipolar disorder and schizophrenia.

However, large scale study needs to be examined for this to be determined.

Question 5

Family studies.

Suicide

Brent 1996

Answer 5

First degree relatives of suicide victims also called suicide pro bands had a greater likelihood of suicide attempts, but it also has to be taken into consideration that they also had an increased risk of other psychiatric disorders.

The suicide probands who had high rates of aggression also had high rates for attempts at suicide.

Question 6

Family studies

Benefits and limitations

Answer 6

+ sample ascertainment
Samples of blended families = easier to obtain than twin and adoption samples

+ Testing hypothesis = if genetically determined we would expect the greatest of correlations for MZ’s than DZ’s and full siblings.

• differences of genetic relatedness accompanied by environmental differences
  … Therefore agree to distinguish genetic and environmental influences.