adoption study - Heston

• The participants in the study were born to schizophrenic mothers in American psychiatric hospital. Children were selected if their mothers had put them up for adoption from birth – the researchers ensured the mother had a diagnosis of schizophrenia and no diseases.
• 58 participants were chosen and matched with a control group on sex, type of eventual placement, and length of time in care.
• Data was collected from several sources including hospital, school, and police records as well as friend interviews.
• Two psychiatrists evaluated the information on each participant blindly and independently. A third evaluation was made by Heston himself. A diagnosis of schizophrenia was given only when all three raters agreed.

  The rate of schizophrenia in those born to schizophrenic individuals was 10.6% compared with 0% in those not born to schizophrenic individuals.
• + having a matched design e.g., controlling gender, and length of time in care minimised participant variables that could have affected internal validity of the results, therefore we can be confident that it is the biological inheritance which caused the difference not environmental factors such as time in care.
• However, not all factors were able to be controlled. For example, the psychiatric status of the father was not checked, so we can’t be sure if this contributed to the participant’s results.

  • Secondary data such as hospital records was collected which could be interpreted subjectively. This might mean they could think a patient is schizophrenic even if their notes didn’t say this.
• + Heston established inter-rater reliability when analysing patient records by using multiple data sources and 3 different raters. Therefore, this provides a reliable interpretation of notes as they were only determined to have schizophrenia if they all agreed.