Interactionist approach

• Interactionist approach

  • Also known as biosocial approach
  • Approach that acknowledges that there are biological, psychological and social factors in the development of SZ.
• What biological factors are included?

  • Genetic vulnerability
  • Neurochemical imbalances
  • Neurological abnormalities
• What psychological factors are included?

  • Stress resulting from life events and daily hassles
• Diathesis stress model


  Proposes both a vulnerability to SZ and a stress-trigger are necessary to develop the disorder.

  One or more underlying factors make a person particularly vulnerable to developing SZ but the onset of the condition is triggered by stress.
• Who created the original diathesis-stress model?

  Meehl
• Original diathesis-stress model

  • Believed diathesis was entirely genetic, the result of a single schizogene.
  • The gene led to the development of a schizotypic personality (sensitive to stress)
  • If a person does not have the schizogene then no amount of stress would lead to SZ
  • In carriers of the gene, chronic stress through childhood and adolescence, in particular the presence of schizophrenogenic mother could result in the development of the condition.
• Modern diathesis-stress model

  • Ripke, many genes increase genetic vulnerability, there is no single schizogene.
  • Ingram and Luxton, trauma becomes the diathesis rather than the stressor.
  • Read et al, early and severe trauma alters the developing brain.
  • Hypothalamic-pituitary-adrenal system can become over-active making the person much more vulnerable to later stress.
• Modern understanding of stress

  • A modern definition of stress includes anything that risks triggering SZ.
  • Houston et al, Cannabis
• How does cannabis increase the risk of SZ?

  • Increases the risk by x7 as it interferes with the dopamine system.
  • However, most people do not develop SZ after smoking cannabis so it seems there must also be one or more vulnerability factors.
• Treatment according to interactionist model

  • Turkington et al, possible to believe in biological causes of SZ and still practise CBT to relive psychological symptoms.
  • Involves adopting an interactionist approach, as it is not possible to adopt a purely biological approach with no psychological significance and use CBT to treat them.
  • Patients tend to be given antipsychotics alongside CBT.
• Treatment in the UK

  • Increasingly standard practise to treat patients with a combination of antipsychotic drugs and CBT.
• Treatment in USA

  • Conflict between psychological and biological models of SZ, which have led to a slower adoption of an interactionist approach.
  • Medication without an accompanying psychological treatment is more common.
• Evidence for the role of vulnerability and triggers

  • Tiernari investigated the impact of both genetic vulnerability and a psychological trigger (dysfunctional parenting).
  • Followed 19,000 Finnish children whose biological mothers had been diagnosed with SZ. In adulthood high genetic risk group were compared to a control group of adoptees without a family history of SZ. Adoptive parents were assessed for child-rearing style, high levels of criticism, hostility were associated with the development of SZ but only in high genetic risk group.
  • Genetic vulnerability+stress= SZ
• How is the original diathesis stress model over-simplistic?

  • Original model portrayed diathesis as a single schizogene and portrayed stress as schizophrenogenic parenting which is too simplistic. Multiple genes in multiple combinations influence diathesis. Stress can come in many forms.
  • Houston et al, found childhood sexual abuse emerged as the major influence on underlying vulnerability to SZ and cannabis as the major trigger.
  • Biological and psychological factors affecting both diathesis and stress.
• Real world application of the interactionist approach

  • Studies shows that combining treatments enhances their effectiveness. Tarrier et al randomly allocated 315 participants to medication and CBT, medication and counselling, medication only.
  • Participants in the 2 combination groups showed lower symptoms following the trial than medication only group, though there was no difference in hospital readmission.
  • Practical advantages to adopting an interactionist approach in terms of treatment outcomes.
• Weak evidence for the role of urbanisation in the interactionist approach

  • SZ is more commonly diagnosed in urban than rural areas. This statistic has sometimes been used to justify the interactionist position. It assumes that urban living is more stressful than rural areas and that the city acts as a big trigger.
  • However it may simply be that SZ is more likely to be diagnosed in cities or people with a diathesis for SZ tend to migrate to cities. Additionally greater population density in Christie’s means that more people tend to witness early symptoms and refer to a doctor.