Interactionist Approach to Schizophrenia


Original Diathesis-Stress Model & Evaluation

Developed by Meehl

  • Diathesis (vulnerability) was completely genetic - only one schizogene triggered by 'schizophregenic mother' 
  • Led to development of 'schizotypic personality' which was vulnerable to stress
  • Without the schizogene no amount of stress could lead to Sz


  • Oversimplistic - Sz is polygenic, so multiple genes increase vulnerability
  • Stress comes in many forms, not just dysfunctional parenting
  • Sz patients who suffer trauma, e.g. childhood abuse, can lead their brain to develop abnormally, meaning that stress becomes diathesis
  • One study - Houston - found that childhood sexual trauma was a vulnerability whilst cannabis was a trigger
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Modern Understanding of Diathesis & Stress


  • There is no single schizogene - Sz is polygenic
  • Include a range of factors beyond genetic, e.g. psychological trauma, so trauma becomes diathesis rather than stress
  • Early childhood trauma affects development of brain - hypothalamic pituitary gland (HPA) system can become overactive, making it more vulnerable to stress


  • Modern definition of stress in relation to diathesis-stress model is anything that increases the risk of developing Sz, not just dysfunctional parenting
  • Research into factors causing Sz is largely concerned with cannabis
  • Cannabis is a stressor - increases risk of Sz by up to 7 times as it interferes with dopamine
  • However most people do not develop Sz after smoking cannabis so there must be other factors
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Evidence for the Role of Vulnerability & Triggers


  • Children adopted from 19,000 Finnish mothers with Sz were followed up
  • Adoptive parents assessed for parenting style  
  • Rates of children with Sz compared to control group with no genetic vulnerability to Sz
  • Parenting style with high levels of criticism and conflict, and low levels of empathy was implicated in development of Sz for those with high genetic risk, but not those in the control group
  • Suggests that both genetic vulnerability and family-related stress are important in the development of Sz
  • Genetically vulnerable children are more sensitive to parenting style
  • Strong support for adopting an interactionist approach to Sz
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Treatment According to Interactionist Approach & E

  • Both biological and psychological factors are acknowledge so both biological and psychological treatments apply
  • Combination of antipsychotics (biological) and CBT (psychological)
  • Turkington - it is possible to believe biological causes of Sz and use CBT to relieve symptoms but this still requires the interactionist model
  • Increasingly common in Britain to be treated with a combination of biological and psychological methods
  • Unlikely to be treated for Sz by just psychological therapies


  • Reseach support for combination therapies rather than just medication
  • Tarrier - Ps randomly allocated (increases internal validity) to either medication+CBT, medication+supportive counselling or control group (medication only)
  • Ps in combination groups showed lower symptom levels than control group but no difference in hospital readmission
  • Superior treatment outcomes shows clear practical advantage to using interactionist therapies, therefore highlights importance of interactionist approach
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