Genetic Explanations

• Heritability of Schizophrenia and Candidate Genes - Gottesman 


  • Gottesman conducted research into the heritability of schizophrenia and found a concordance rate of 48% for schizophrenia between monozygotic twins
  • The closer the genetic link between you and someone with schizophrenia, the higher the chance of also developing the disease.
• Candidate genes 


  • There is no single gene that has been identified as causing schizophrenia rather it is thought to be an effect of several genes combined.
  • These genes may increase a person's risk of developing schizophrenia known as candidate genes and are referred to as polygenic.
• Evaluation - Clinical and Objetive

  Methods used to measure a genetic explanation for schizophrenia are clinical, objective and not affected by sources of bias such as individual differences which means they have good reliability and validity.
• Weakness - Isn't full genetic

  Genetic is an explanation of schizophrenia but not the only one as if schizophrenia was purely biological then concordance rated for MZ twins would be 100% which no research has ever found.
• Weakness - Varied symptoms 


  The symptoms of schizophrenia are varied and will not present the same way in every person - the absence of a biomarker means that a genetic perspective is very difficult to know definitively of a patient actually has schizophrenia or if they have another disorder.
• Why are adoption studies useful when trying to understand if a trait has a genetic basis?

  Environmental factors (upbringing) and genetic factors (biological parents) can be separated.

  If a trait is genetic, you would expect high concordance between the child and genetic parent.
• Adoption studies - Research

  Tienari et al (2004): Biological children of parents with schizophrenia are at a heightened risk even if they grow up in an adoptive family.
• Candidate Genes - Research

  
  

  Ripke et al (2014): compared the genetic makeup of 37,000 patients with 113,000 controls and found 108 genetic variations associated with an increased risk of getting the disorder.

  Supports the idea that schizophrenia is aetiologically heterogenous – different combinations of factors can lead to the condition.
• Strength - Genetic Explanations

  Family studies such as Gottesman show that risk increases with genetic similarity to a family member with schizophrenia. Adoption studies, such as Tienari et al (2004) show a heightened risk of schizophrenia if the biological parents had schizophrenia.

  This suggests that multiple studies with differing research methods have come to the same conclusion, that people are more vulnerable to schizophrenia as a result of their genetic make-up.
• Mrokved et al (2017) - environmental factors 


  Found that 67% of people with schizophrenia reported to least one childhood trauma compared to 38% of a matched group of non-psychotic individuals with mental health problems.

  Which suggests that genetic factors alno can't provide a complete explanation.