Biological Explanations of schiz- Gottesman and Shields genetics Flashcards
What is the genetic hypothesis:
Controlled genetic studies have shown that the risk for a particular individual is proportional to the amount of genes they share.
Schizophrenia appears to run in families.
What is the assumption underlying this research?
It’s the monozygotic twins will show greater concordance rates than dizygotic twins.
This is because MZ twins are genetically identical whereas, DZ twins only share about 50% of the same genes.
Gottesman and Shields study:
What is the aim of the study?
The aim of the study was to see to what extent schizophrenia was caused by genetics or environmental factors, seeing if there would be a higher concordance rate between MZ twins compared to DZ twins (where both twins would suffer with schizophrenia).
Gottesman and Shields study:
Participants
Selected 57 pairs of twins from a potential 392, where at least one of each pair suffered from schizophrenia.
They eliminated people from the sample that were from different cultures and those that tests didn’t clearly identify if they were MZ or DZ twins.
Gottesman and Shields study:
Procedure: looking at records
Researchers looked at patient records from a short-stay psychiatric hospital with a large outpatients department.
The records covered a 16 year history from 1948 to 1964
Gottesman and Shields study:
Procedure:
What did they do to determine whether they were MZ or DZ twins and whether they suffered from schizophrenia or another mental illness?
- they used finger prints, blood tests and saw whether they look alike to determine if they were MZ or DZ.
- then used hospital notes, case histories, recorder semi-structured interviews of their verbal behaviour and personality tests to determine if they suffered from schizophrenia or another form of mental illness.
Gottesman and Shield study:
Procedure: what were they looking for?
Researchers wanted to look at concordance rates.
If the one twin had been diagnosed with schizophrenia, they wanted to know how often their counterpart twin would also be diagnosed with schizophrenia.
Gottesman and Shields study:
What is the patient who had been admitted to the psychiatric hospital first called?
Proband
The data was analysed between each proband and their twin.
Gottesman and Shields study:
Results:
Concordance rate where both twins clearly suffered from schizophrenia was 42% for MZ twins, and 9% for DZ twins.
Gottesman and Shields study:
Conclusion:
The findings suggested that the closer the genetic relationship between two people, the greater the likelihood that if one of them is diagnosed with schizophrenia, the co-twin is also going to develop schizophrenia.
The study also showed that this relationship was more prevalent among females than males.
Gottesman and Shields study:
Strengths: sample
-study ensured sample was tightly controlled. It didn’t include twins from different cultures as they could have been wrongly diagnosed suffering with schizophrenia (good internal validity).
Gottesman and Shields study:
Strength: reliability
Several studies have looked at twins and concordance rates of schizophrenia, all showing similar findings to Gottesman and Shields - suggests the results of this study are reliable.
Gottesman and Shields study:
Strength: collecting data from various sources
This gives greater reliability to the study
Gottesman and Shields study:
Weakness: problems with the twin studies research method
In twin studies, MZ twins tend to be treated more alike than DZ twins and this could be the reason for the difference in results rather than the genetic link suggested by G and S.
Gottesman and Shields study:
Weakness: sample
Sample taken from USA and any twins from other ethnic backgrounds removed meaning the study was ETHNOCENTRIC and can only be generalised to white Americans only.
