27 terms

Gottesman and Shields

A study looking at the links between genetics and Schizophrenia.
STUDY
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What is the date of the Gottesman and Shields study?
1966
Aims
Is there a genetic link with schizophrenia?
They wanted to replicate earlier studies that found a link.
What type of data did they use?
Secondary
Where did they get their data?
A hospital in the USA
Who did they look at to get their data?
Twins where at least one twin had schizophrenia
When did the original study take place?
1948
How long did the original study last?
16 years
How many patients did they look at?
392 in total
How many twins did they include in the study?
62 (31 males and 31 females)
How many twins in the study sample both had schizophrenia?
5 twins were both diagnosed with schizophrenia
How did the researchers test if the twins were MZ or DZ?
Blood tests and visual tests
How was the data gathered?
Data was gathered from hospital notes (secondary data), from interviews (primary data), personality tests (primary data) and tests for thought disorders (primary data).
What did the researchers look for in addition to schizophrenia?
Other related psychoses and mental health issues
What is a concordance rate?
This is how often, in the case of this study, if one twin is diagnosed with schizophrenia or a related psychosis, the other twin also has it.
How did Gottesman and Shields handle the gathered data?
They divided the results according to whether the twins were MZ or DZ to see if the concordance rate was higher for MZ twins.
What results did Gottesman and Shields expect to find?
They expected to find that the concordance rate for schizophrenia would be higher in MZ twins.
How many MZ twins had schizophrenia when their twin also had it?
10 pairs - 42% of cases
How many DZ twins had schizophrenia when their twin also had it?
3 pairs - 9%
How many MZ twins had schizophrenia when their twin also had it or had an associated psychosis?
13 pairs - 54%
How many DZ twins had schizophrenia when their twin also had it or had an associated psychosis?
6 pairs - 18%
In the most severe cases of schizophrenia, how many MZ twins had schizophrenia when their twin also had it or had an associated psychosis?
between 75% and 91%
What was the conclusion of the Gottesman and Shields study?
There was evidence that MZ twins are more likely to both have a diagnosis of schizophrenia and related disorders than DZ twins. This is evidence that there is a genetic link.
Why can we not say that genetics are solely responsible for schizophrenia?
If genetics were solely responsible for schizophrenia, the concordance rate for MZ twins would be 100%.
What could play a part in the onset of schizophrenia aside from genetics?
Environmental factors
What is the diathesis-stress explanation for schizophrenia?
This says that a person can have a genetic predisposition, but that environmental factors act as a trigger for the illness.
Some genes may lower a persons' threshold for dealing with stress and predispose them to schizophrenia.
What are the strengths of the Gottesman and Shields study?
The findings of the study were backed up by other studies (Inouye (1961) - Japan). This suggests that the results are RELIABLE.
MZ and DZ twins were carefully identified and a lot of data was gathered to confirm diagnosis.
What were the weaknesses of the Gottesman and Shields study?
The term 'related psychosis' is vague and the severity of the schizophrenia was used in the categorisation of the results, but there is subjectivity here.
They suggested that there are types of schizophrenia and some may come from life experiences. In their results, the different types weren't identified.