Interactionist Approach

• Diathesis-stress model

  vulnerability and stress-trigger can develop schizophrenia
• Meehl's 1962 original model

  • diathesis was genetic due to a single schizogene which led to a biological schizotypic personality
  • no stress would lead to schizophrenia if person doesn't have schizogene
  • chronic stress in carriers of the gene through childhood could lead to schizophrenia
• diathesis

  vulnerability
• stress

  negative psychological experience
• schizotypic personality

  one characteristic of which is sensitivity to stress
• modern understanding of diathesis - many genes increase genetic vulnerability

  • Ripke 2014 - no single 'schizogene'
  • Ingram & Luxton 2005 = psychological trauma - trauma is the diathesis not stressor
  • Read 2001 = neurodevelopment model
• Read 2001 - neurodevelopment model

  early trauma alters brain development - HPA system can become over-active which makes person more vulnerable to later stress

  eg child abuse
• HPA system

  hypothalamic-pituitary-adrenal
• modern understanding of stress

  Houston 2008 = anything that risks triggering schizophrenia

  • cannabis - a stressor as it increases risk up to 7x because it interferes with dopamine system
• interactionist

  biological and psychological factors develop schizophrenia
• early version of diathesis-stress model

  vulnerability = genetic

  triggers = psychological
• modern version of model

  genes & trauma = diatheses

  stress = psychological or biological
• treatment

  combining psychological therapies - CBT - and antipsychotic medication

  unusual to treat solely with psychological therapies - CBT, family therapy and token economies used on patients taking antipsychotics
• interactionist treatments


  Brits use CBT & antipsychotic drugs whereas USA's conflict between both delayed adoption of interactionist approach therefore medication without psychological treatment is more common in USA.
• Support - evidence of vulnerability and triggers

  • Tienari 2004 = high levels of criticism, hostility and low levels of empathy in adoptive parents of 19,000 Finnish adoptees with schizophrenic mother
  • high genetic risk comes from schizophrenic biological mother; compared with low genetic risk group (adoptees with none); adoptive parents' child rearing style was the trigger for developing schizophrenia
  • therefore combination of genetic vulnerability and dysfunctional parenting/trigger increases risk of schizophrenia
• Limitation - over-simplicity of OG model

  • Meehl 1962 = diathesis from single schizogene; stress is psychological form schizophrenogenic parenting - too simplistic
  • Houston 2008 = childhood sexual abuse can create vulnerability, cannabis as the trigger
  • multiple factors affect diathesis and stress
  • therefore supports the modern model
• Support - application to treatments

  • Tarrier 2004 = combination of CBT/counselling and medication lowers symptoms better than only medication; no difference in hospital admission
  • enhanced effectiveness when combining biological and psychological
  • therefore practical advantage of interactionist approach for treatments
• CA to application/Logical error

  treatment-causation fallacy

  • Jarvis & Okami 2019 = alcohol reduces shyness therefore a lack of it causes shyness
  • incorrect to assume success of combined treatments makes interactionist explanations right
• Tarrier 2004


  randomly allocated 315 participants

  1. medication + CBT
  2. medication + counselling
  3. medication

  lower symptoms in 2 combination groups; no difference in hospital admission