Interactionist Approach in Explaining and Treating SZ

• What does the diathesis-stress model propose about schizophrenia (SZ)?

  It results from psychological and biological influences
• How do symptoms of SZ relate to stressors and biological vulnerability?

  Symptoms worsen with stressors and biological vulnerability
• Why do not all genetically predisposed individuals develop SZ?

  Because environmental factors also play a role
• What is the genetic component of diathesis in SZ?

  It refers to genetic vulnerability to the disorder
• What did Tienari et al find regarding identical twins and SZ?

  Identical twins have a higher risk than siblings
• What does the disconcordance among identical twins suggest?

  Environmental factors influence the development of SZ
• What modern factors are included in the understanding of diathesis?

  Factors beyond genetics, including trauma
• What does Read's neurodevelopmental model propose?

  Early trauma alters brain development, increasing vulnerability
• What types of stressful life events can trigger SZ?

  Childhood trauma and urban living stresses
• What did Varese et al find about children and trauma?

  Children with severe trauma are three times more likely to develop SZ
• How does the level of trauma relate to the risk of developing SZ?

  Higher trauma levels increase the risk of SZ
• What is a modern understanding of stress in relation to SZ?

  Anything that triggers symptoms of SZ
• What recent research has focused on as a trigger for SZ?

  Cannabis use
• Why is cannabis considered a stressor for SZ?

  It increases SZ risk by up to seven times
• How does cannabis interfere with the risk of SZ?

  It interferes with the dopamine system
• How do diathesis and stress interact to lead to SZ?

  • Minor stressors can trigger SZ in highly vulnerable individuals
  • Major stressors can trigger SZ in those with low vulnerability
  • This suggests an additive relationship between diathesis and stress
• What does the additive nature of diathesis and stress imply?

  They combine to produce the disorder
• Diathesis-Stress Model AO3 - Real world application


  • Tarrier et al - patients allocated to one of three conditions, where the last control group received no treatment and the first two groups received a combination of psychological and biological treatments
  • After an 18 month follow-up, "there were significant advantages for CBT and supportive counseling over TAU alone on symptom measures, no group difference was seen for relapse or re-hospitalisation”
  • Adjunctive psychological treatments can have a beneficial long-term effect on symptom reduction
• Diathesis-Stress Model AO3 - Over-simplistic


  • Most diathesis-stress models emphasise ‘vulnerability’ in terms of genetic influences alone
  • Ex. Ripke et al - over 108 candidate genes, each slightly increasing the risk of SZ, and so there is no single 'schizogene'
  • Stress can come in many forms apart from the schizophrenogenic mother or dysfunctional parenting - high levels of expressed emotion, childhood trauma (Read et al) and the excessive use of cannabis (Houston et al)
  • Therefore, the diathesis is not exclusively biological, nor is the stressor exclusively psychological.
• Diathesis-Stress Model AO3 - Support for vulnerability 


  • Tienari et al - used research from mothers and adoptees who suffered from SZ and compared these findings to a neurotypical group adopted across the same period
  • Adoptive parents - high levels of critics, hostility and low levels of empathy were strongly associated with the development of SZ but only in the genetic risk group
  • Therefore, this provides strong support for the diathesis-stress model because the findings demonstrate that a single diathesis is not enough to trigger the development of SZ