biological: the genetic basis of schizophrenia

the heritability of schizophrenia & candidate genes

• Gottesman (1991) conducted research into the heritability of schizophrenia and found a concordance rate of 48% between MZ twins

• There is no single gene that has been identified as causing schizophrenia; rather, it is thought that the condition is polygenic

• Salleh (2004) conducted research into molecular genetics, identifying some candidate genes of schizophrenia

  • Neuregulin 1, dysbindin and proline dehydrogenase

  • These candidate genes are all implicated in the production and regulation of key mood-related neurotransmitters dopamine, serotonin and glutamate

research which investigates the genetic basis of schizophrenia

• McCarroll et al. (2016) analysed the genomes of 65,000 people and 700 postmortem brains

  • Found that the strongest known genetic risk of schizophrenia comes from the gene C4

• Haraldsson (2011) conducted a meta-analysis

  • Found strong evidence for the heritability of schizophrenia

  • Found that some candidate genes, in combination with each other, result in a person having an increased vulnerability to schizophrenia compared to other combinations of candidate genes

strengths of genetic basis of schizophrenia

• 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 that they have good reliability and validity

• There is now a huge and compelling body of research evidence which points to genetics playing a key role in the development of schizophrenia

weaknesses of genetic basis of schizophrenia

• Genetics is only one explanation of schizophrenia

  • If schizophrenia was purely biological, then concordance rates for MZ twins would be 100%, which no research has ever found

• The symptoms of schizophrenia are varied and will not present in the same way per person - the absence of a biomarker means that from a genetic perspective, it is very difficult to know definitively if a patient actually has schizophrenia or if they have another disorder altogether

link of genetic explanation for schizophrenia to issues & debates

• The genetic explanation exemplifies the nature side of the nature-nurture debate, suggesting schizophrenia is largely inherited through candidate genes

  • The fact that MZ twins only show a 48% concordance rate (Gottesman, 1991) suggests that environmental factors must also play a key role

  • The most valid explanation is likely to be interactionist, combining genetic vulnerability with environmental triggers (diathesis-stress model)

• Focusing on candidate genes as an explanation for schizophrenia is biologically reductionist

  • This is because it simplifies a complex disorder to genetic and neurochemical factors alone

  • This ignores psychological, social, and environmental influences, such as trauma, family, dynamics, or life stress, which can also contribute to the disorder