Genetic basis

• Schizophrenia


  A mental disorder which runs in a family's genetics
• Family studies on schizophrenia

  • Gottesman (1991) studied the relationship between families and schizophrenia
  • Someone with an aunt with schizophrenia only has a 2% chance of development
  • Someone with a sibling with schizophrenia has a 9% chance of development
  • Someone with an identical twin who has schizophrenia has a 48% chance of development
  • There is a strong relationship between genetic similarity and vulnerability/risk of developing schizophrenia
• Candidate genes


  Early research focused on finding a single faulty gene that would result in schizophrenia, but schizophrenia is now thought to be polygenic - a result of multiple different genes
• Ripke et al (2014) study


  1. Combined all previous genomic research on schizophrenia

  2. Looked at the genetic make-up of 37,000 people with a diagnosis of schizophrenia

  3. Compared them to 113,000 controls

  4. Found 108 separate genetic variations associated with a risk of schizophrenia
• Schizophrenia is thought to be aetiologically heterogeneous - a different combination of genes can lead to schizophrenia
• The role of mutation

  • Brown et al (2002) - 0.7% risk with fathers under 25 and 2% risk with fathers over 50  
  • Increased risk is thought to be because of increase chance of mutations in older ages 
• Research support - 😊  

  • Strong evidence for the genetic basis of schizophrenia  
  • Tienari et al (2004) - shows that biological children of parents with schizophrenia are at a heightened risk of developing schizophrenia even if they grow up with an adoptive family
  • Hilker et al (2018) - showed a concordance rate of 33% for identical twins and 7% for non-identical twins 
  • Evidence from adoption and twin studies, some people are vulnerable to schizophrenia as a result of their genetic make-up
• Environmental factors - 🙁  

  • Clear evidence that environmental factors increase risk
  • Biological risk factors include birth complications - Morgan et a (2017). Smoking THC cannabis in your teenage years - Di Forti et al (2015)  
  • Psychological risk factors include childhood trauma which may leave individuals more susceptible to adult mental illness.  
  • Morkved et al (2017) - 67% of people with schizophrenia and related psychotic disorders have reported at least one childhood traumas  
  • This demonstrates how the development of schizophrenia can-not be due to only genetic factors.