Genetic explanation

• Schizophrenia is a real illness, just like any physical illness
• Schizophrenia has a physical cause- microorganisms, genes, biochemistry or neuroanatomy
• Diagnosis leads to appropriate physical treatments
• There is more than 1 gene responsible for schizophrenia
• If a person had multiple genes responsible for schizophrenia, their overall vulnerability increases
• Research methods: twin studies and adoption studies to assess concordance rates
• Gottesman (1991)

  • General population have a 1% chance of developing schizophrenia
  • If one monozygotic twin has schizophrenia, the other has a 48% chance of developing it
• As the percentage of genes shared increases, the percentage likelihood of developing schizophrenia increases
• Parmas (1993)

  • 16% of children whose mothers has schizophrenia developed it
  • 2% of children whose mothers did not have schizophrenia developed it
• Kety and Ingraham (1992)

  • Prevalence rates of schizophrenia were 10x higher among genetic than adoptive relatives of schizophrenia
• A schizophrenia working group analysed the DNA of 36,989 schizophrenics and 11,300 non-schizophrenics- found 128 independent genetic variations
• Gottesman and Shields (1991)

  • Reviewed 5 twin studies
  • Concordance rate of up to 91% for MZ twins with severe schizophrenia
• Candidate genes: people are 1.4x more likely to develop schizophrenia if they have an abnormality in the DISC1 gene (Kim et al, 2012)
• The DISC1 gene contributes to the processing of GABA, one of the main inhibitory neurotransmitters in the brain which is integral in regulating dopamine, left unregulated this can lead to positive symptoms
• Genetic explanations don't just relate to inheritance

  • DiGeorge Syndrome is caused by the deletion of 30-40 genes on chromosome 22
  • 25% of people with DiGeorge Syndrome go on to be developed with schizophrenia
  • DiGeorge Syndrome is rarely inherited