Adoption study (Kety)

• Adoption studies are more useful than twin studies when investigating environmental influences on behaviour because adoptees grow up in different families compared to twins who share the same family. Adoption studies are therefore better at separating out the effects of biology and environment on behaviour. They are also more ethically acceptable than twin studies since adoptees are separated from their birth parents at birth rather than being separated later in life.
• The main limitation of adoption studies is that they rely on retrospective self reports, which may not always be accurate. For example, adopted children may remember things incorrectly or lie about their experiences growing up. Additionally, some adoptive parents may not want to participate in research studies, leading to selection bias.
• Aim of kety et al?

  To establish if there is a genetic basis for schizophrenia
• Sample for kety et al

  • 34 schizophrenic patients were taken from the danish adoption register
  • Aged 20-43 and split into 3 groups chronic sufferer, short term sufferer or had a borderline diagnosis
  • 33 healthy controls matched on gender, age when they were adopted and social class of adoptive family
• Procedure for kety ET al

  • Split into 3 groups chronic sufferer, short term sufferer or borderline diagnosis
  • Mental health register used to assess mental status
  • Diagnosed by psychiatrists who didn’t know family members (blind test )
  • Were diagnosed as either:
  • B - just like adoptive child
  • D - uncertain level of schizophrenia
  • C - inadequate personality
• Key et al results

  Found more signs of schizophrenic disorders in biological family than their adoptive families. Of 150 biological relatives 8.7% had diagnosis of schizophrenia compared to 1.9% of control sample
• Kety et al conclusion

  Schizophrenia seems to have a genetic component as adoptees were more likely to have schizophrenia in their biological family than their adoptive family.