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Gottesman and shields
Gottesman and Shields (1966) carried out a study into whether schizophrenia might be caused
genetically. They compared MZ and DZ twins to see how often when one twin had been diagnosed
with schizophrenia the other had a similar diagnosis.
Previous twin studies had shown a difference in concordance for schizophrenia between MZ and DZ
twins and had concluded that there is a genetic basis for schizophrenia. However, the methodology
of these studies had been criticised. Gottesman and Shields set about their study with such critisisms
in mind and were careful to detail their sampling to address such criticisms. The research method is a
twin study; both primary and secondary data are gathered.
To study twins, at least one of whom had been diagnosed with schizophrenia, to see
whether schizophrenia had a genetic basis.
To replicate other studies to see how far their findings agreed with each other and with their
The researchers accessed records from 1948 from the Maudsley and Bethlem Royal Joint Hospital.
There were 16 consecutive years in which information about twins had been recorded. By March
1964, there had been 392 patients of the same sex who said they were twins; 47 had been
diagnosed with schizophrenia. Other twins were diagnosed in such a way that suggested they may
have schizophrenia. Most twins were followed up who were known to have been diagnosed with
schizophrenia after they had left the hospital. 21 more pairs were found. Altogether 68 patients
were one of pairs of twins and had a diagnosis of schizophrenia or a related psychosis.
Three tests were used to measure zygocity:
-resemblance between the twins
There were 24 MZ pairs, 33 DZ pairs.
Data were collected by, using hospital notes, case histories for the twins, tape recordings,
personality testing, a test to examine thought disorders.
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Category 1 both twins had been diagnosed with schizophrenia
Category 2 One twin had schizophrenia, the other twin had been given another diagnosis related
Category 3 the co-twin had some psychiatric abnormality, but nothing related to schizophrenia
Category 4 Pairs with normal limits
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 or…read more