Genetic

• What did Gottesman’s 1991 Family study find in terms of risk of developing schizophrenia

  • there is a strong genetic component
  • As genetic similarity increases, so does the probability of having schizophrenia
  • Identical twins have 100% shared genes by only 48% risk so we know there is something else at play- genetic risk factor not cause
• What do Twin studies show for inheritance or risk of developing schizophrenia

  Joseph (2004) calculated that pooled data for all schizophrenia twin studies carried out prior to 2001 showed a concordance rate for MZ twins of 40.4% and 7.4% for DZ twins
• What do adoption studies show for inheritance or risk of developing schizophrenia

  Tienari et al (2000)

  Of the 164 adoptees whose biological mothers had been diagnosed with schizophrenia, 11 (6.7%) also received a diagnosis of schizophrenia

  Compared to just 4 (2%) of the 197 control adoptees, who were born to non-schizophrenic mothers

  = strong genetic link to schizophrenia
• What do genome studies show for inheritance or risk of developing schizophrenia

  Ripke et al (2014)

  Combined all data from previous genome-wide studies of schizophrenia

  The genetic makeup of 37,000 people with a diagnosis of schizophrenia was compared to 113,000 controls

  108 separate genetic variations were associated with slightly increased risk of schizophrenia
• How can there be a genetic link without family history of schizophrenia

  Can be caused by a mutation in parental DNA which can be caused by radiation, poison or viral infection, as well as occurring spontaneously

  Brown et al (2002): positive correlation between paternal age (associated with increased risk of sperm mutation) and risk of schizophrenia, increasing around 0.7% with fathers under 25 to over 2% in fathers over 50
• AO3: Other influential factors- Environmental

  Morgan et al - Birth complications

  Di Forti et al - Cannabis
• How do Birth Complications increasing the risk of schizophrenia challenge genetic explanations- Morgan et al

  Suggests that early-life environmental factors can have a profound influence on its development, indicating it is not solely determined by inherited genetic predispositions
• How does Cannabis increase the risk of developing schizophrenia

  Di Forti et al

  Found that high potency cannabis use, especially in teenage years (3x more likely) impacts brain development, significantly increasing the risk of psychosis
• How does Cannabis increasing the risk of schizophrenia contradict genetic explanations

  Shows external factors, such as substance use, can independently contribute to the onset, challenging the idea of it being solely genetically predetermined
• How do psychological risks of developing schizophrenia challenge genetic explanations

  Mørkved et al (2017) found that exposure to childhood trauma such as abuse or neglect, was strongly associated with an increased risk of developing schizophrenia.

  This challenges genetic explanations by demonstrating that adverse environmental experiences in early life can play a critical role in its development
• Real world application supporting genetic explanations

  Genetic Counselling

  • Can help parents understand the hereditary risks of schizophrenia by providing information about the likelihood of passing on genetic predispositions.
  • Offering guidance on preventative measures or early interventions.
  • Can reduce anxiety & support informed decision making, and help parents create environments that minimise potential risk factors for their children