Gottesman and Shields

Question 1

aim ?

Answer 1

to explore the extent to which schizophrenia is a heritable condition, by comparing concordance rate of MZ and DZ twins where one of each pair already has schizophrenia (plus how this also relates to other psychiatric disorders)

Question 2

what was the procedure for collecting the secondary data ?

Answer 2

• looked at 16 years of hospital records from maudsley and bethlem royal joint hospital
• 392 were same sex twins
• 47 of them were diagnosed with schizophrenia

Question 3

what was the final sample ?

Answer 3

57 twin pairs:

• 24 MZ
• 33 DZ
• 31 of each gender
• 6 extra twin pairs were not allowed in the sample (3 of them were form overseas which may have invalidated the diagnosis - cultural differences)

Question 4

what was the procedure for the primary data ?

Answer 4

• researchers conducted semi-structured interviews (verbal behaviour analysed)
• conducted personality test and test for thought disorder

Question 5

what was done to improve the validity (part of the procedure) ?

Answer 5

blood tests, fingerprint analysis, and an assessment of physical resemblance was done to validate the zygocity of the twins

Question 6

what were the findings ?

Answer 6

• concordance of both being schizophrenic: MZ(%)=42 | DZ(%)=9
• the second being schizophrenic or with some other clinical disorder: MZ(%)= 79 | DZ(%)=45

Question 7

what was the finding for the gender differences ?

Answer 7

concordance was higher for females

Question 8

what were the most severe findings ?

Answer 8

concordance rates of 75%-91% for MZ twins and only 22% for DZ twins

Question 9

what’s a weakness of the study ?

Answer 9

its sample size was very small and so this could be a type one error

Question 10

what are the conclusions for the study ?

Answer 10

• genes play an important role in schizophrenia because concordance was higher in MZ than DZ
• however, situational factors must also play a role as otherwise concordance would have been 100% for MZ