Gottesman and Shields (1972)

Aims

To review previous research on genetic transmission of schizophrenia.

Procedures

A review article of adoption and twin studies between 1967 and 1976 – 3 adoptions and 5 twin studies.

711 participants in adoption studies. 210 monozygotic and 319 dizygotic in twin studies.

The concordance rate of schizophrenia in adopted children and monozygotic twins was extrapolated.

Findings

• All adoption studies – increased concordance rate in adopted children with schizophrenic biological parent.
• Kety (1968) found that biological siblings of children with schizophrenia showed a higher percentage of the mental disorder.
• All twin studies – higher concordance rate for schizophrenia in monozygotic twins.
• In Gottesman and Shields (1966) the rate was 58% for MZ and 12% for DZ.

Conclusions

The closer the genetic relationships between two people, the higher the chance that if one of them is diagnosed with schizophrenia, the higher the chance that the other will too.

However, the concordance rates were not 100%, which leads researchers to assume that the environment plays a part in triggering the disorder.

Strengths:

• Large sample – high level of reliability and generalisability.
• Validity – quantitative elements allows results to be easily compared and analysed.
• Cross referencing – 8 studies are used in the research, which makes it more reliable and applicable to the wider population.

Weaknesses:

• Secondary research – the use of other research does not eliminate researcher bias or other issues, which may make the results less valid, reliable and ethical.
• Reductionist – the study assumes that no other factors outside of genetics can cause schizophrenia.