To find out if there is a genetic
basis for schizophrenia
DESIGN
independent groups design because it
looks at the difference between
biological drelatives and adoptive
relatives of schizophrenia-sufferers
As adoption and
schizophrenia are
naturally-occurring
variables, this is a natural
experiment.
DV
The researcher's measured the
prevalence of
schizophrenia-related mental
illness among family members.
SAMPLE
34 schizophrenic patients taken from the
Danish Adoption Register for Copenhagen
33 mentally-healthy
Controls were selected
from the Danish Adoption
Registry.
PROCEDURE
Kety used the Danish family
records to locate adoptive and
biological relatives of all the
participants.
e tracked down 463 relatives
and used the mental health
register to assess their mental
status.
A panel of 4 Danish psychiatrists
used the medical records to
diagnose the family members.
Once the diagnoses had been made, the
identities were revealed and they were
assigned to adoptive family groups (IA and
CA) or to the biological family groups (IB or
CB).
RESULTS
The research found more signs of schizophrenic
spectrum disorders in the index participants' biological
family than their adoptive family
They found more spectrum disorders in the
index participants' biological families than in the
Controls' biological families.
CONCLUSION
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
EVALUATION
GENERALISABILITY
This study has a fairly
large sample and covers a
range of ages
RELIABILITY
Very reliable procedure and they replicated it in 1975, 1978 and 1994
APPLICATION
For families with a
history of
schizophrenia and
people looking to
adopt a child.
VALIDITY
Kety's American-Danish Adoption
Studies tie in with earlier research
like Gottesman & Shields (1966)
ETHICS
The participants in this
study were not directly
approached: only their
data was analysed by the
researchers
This could be done under Danish laws without needing consent from the participants.