Genes

• Family studies

  Gottesman's study found that someone with an aunt with SZ has a 2% chance of developing it, 9% for a sibling and 48% for an identical twin.

  -> suggests that there's a strong relationship between the degree of genetic similarity and shared risk of schizophrenia.
• Candidate genes

  Schizophrenia is polygenic = it's influenced by multiple genes working together rather than just one.

  Ripke et al. combined all the data from genome studies and found 108 separate genes that are associated with an increased risk of developing schizophrenia.
• Mutation

  Schizophrenia can be caused by a mutation in parental DNA.

  Evidence shows that there is an association between paternal age (increased risk of sperm mutation) and a risk of schizophrenia.
• AO3 - Family studies

  Strength) Strong evidence base

  Family studies show risk of SZ increases with genetic similarity. Twin study found 33% concordance rate for MZ and 7% for DZ. Also, adoption studies found that biological children of parents with SZ are at greater risk of developing it, even if they grow up in an adopted family.

  -> shows that people are more vulnerable to SZ because of their genes.
• AO3 - Environmental risk factors

  Limitation) Biological risk factors include birth complications and smoking THC-rich cannabis in teenage years. Psychological risk factors include childhood trauma.

  -> This means genes alone don't provide a complete explanation for SZ.