11. Adoption Study- Kety Flashcards
What was the aim of Kety et al’s (1968) adoption study?
To find out if there is a genetic basis for schizophrenia.
In particular, the researcher compares the adoptive family and the biological family of a schizophrenia sufferer (the index participant) to see if there is a higher rate of schizophrenia related illness among biological relatives than adoptive relatives.
(Nature VS Nurture)
What was Kety’s independent variable?
Independent groups design:
-Whether the adoptee had schizophrenia or not.
(It looks at the difference between biological relatives and adoptive relatives of schizophrenia-sufferers and the difference between the schizophrenia-sufferers and a control group with no history of mental illness).
What was Kety’s dependent variable?
The researcher’s measured the prevalence of schizophrenia related mental illness among family members.
Where did Kety obtain his sample from?
-Denmark keeps a complete record of adoptions in the Danish Adoption Register, which includes children born as far back at 1924.
-It includes details of both the biological and adoptive families, making large scale family research much easier in Denmark than in many other countries.
-Denmark makes this information public along with information from the mental health register, enabling researchers to make links between people on the adoption register to people on the mental health register.
Describe the experimental group.
Opportunity sample:
-34 schizophrenic patients (2 of them MZ twins) taken from the Danish Adoption Register for Copenhagen.
-They were aged 20 to 43 and were taken from a larger sample of 503 adoptees who had been admitted to psychiatric hospitals with general mental illnesses.
-B1 was a group of 16 patients with chronic (long term) schizophrenia.
-B2 was a group of 7 with acute (short term or one off) schizophrenia.
-B3 was a group of 11 with ‘borderline schizophrenia’ or ‘latent schizophrenia’.
Describe the control group.
-33 mentally healthy controls were selected from the Danish Adoption Registry.
-They were matched to schizophrenic patients on age, gender, the age at which they were adopted and the social class of the adoptive family.
How did they locate the family members and what did they use for data?
-Kety used the Danish family records to locate adoptive and biological relatives of all the participants.
-He tracked down 463 relatives and used the mental healthy register to assess their mental status.
What categories were the relatives of the participants classed into?
The psychiatrists diagnosed the family members in these categories, just like the index participants:
-B1: Chronic (long term) schizophrenia.
-B2: Acute (short term or one off) schizophrenia.
-B3: ‘Borderline schizophrenia’ or ‘latent schizophrenia’.
Because the psychiartrists had to work from medical records, they were uncertain about their diagnosis sometimes, hence the D1-D3 categories:
-D1: ‘Uncertain chronic schizophrenia’
-D2: ‘Uncertain acute schizophrenia’
-D3: ‘Uncertain borderline schizophrenia’
C: Schizoid or ‘inadequate personality’
They were unable to decide about 4 of the relatives who were therefore not included in the results.
Who analysed the data?
A panel of 4 Danish psychiatrists used the medical records to diagnose the family members.
How did they diagnose?
-It was a ‘blind test’ because the psychiatrists did not know whether the records were from an adoptive or biological family member.
-Once diagnoses had been made, identities were revealed and they were assigned to adoptive family groups (IA and CA) or biological family groups (IB or CB).
What was the result for the biological family compared to adopted families?
More signs of schizophrenia in biological family than adoptive family.
What was the result for the control group compared to biological?
IB (index biological): 13 with schizophrenic spectrum symptoms, 8.7%
CB (control biological): 3 with schizophrenic spectrum symptoms, 1.9%
What did Kety’s study conclude?
There seems to be a genetic component to schizophrenia because schizophrenic adoptees were more likely to have schizophrenia in their biological family than their adoptive family and their biological families were more likely to have schizophrenia than the families of controls.
