Key Research

• Gottesman aimed to investigate the genetic transmission of psychological disorders if both parents had the same disorder, as well as the consequences for offspring if parents had two different disorders. This study aimed to add to previous research, but with a much larger sample in order to obtain more conclusive findings.
• Gottesman used the Danish Central Psychiatric Register used to identify people; this was in the public domain and anonymised so no ethical consent needed. A sample of 2.6 million people from Denmark who were born from 1968-1997, with a link to their mother and father. From the population three groups were identified:

  • Both parents had been diagnosed with schizophrenia or bipolar disorder and had been admitted to a psychiatric facility.
  • One parent had been diagnosed with schizophrenia or bipolar disorder and had been admitted to a psychiatric facility.
  • Neither parent admitted with a diagnosis
• Gottesman found that the risk of developing schizophrenia if both parents had the disorder was 27%.

  If one parent had schizophrenia the child’s risk was 7 %,

  While in the neither parent group it was 0.86%.

  There is a super high risk of developing any disorder (68 %) if both parents have schizophrenia.
• Gottesman concluded that children of 2 parents with psychosis have a "super high risk" of psychosis. The risk of offspring being admitted to hospital with a diagnosis of schizophrenia is higher if both parents have been admitted with this disorder vs those with one/neither parent admitted with the diagnosis. These conclusions are also true for bipolar disorder. These findings provide strong evidence to support the genetic explanation of mental illness. These risks may be useful and informative for genetic counselling to inform personal decisions in relation to marriage and family planning.