Interactionist approach to schizophrenia

• Diathesis-stress model= vulnerability + trigger (negative psychological experiences)= schizophrenia
• The diathesis-stress model says both a vulnerability and a stress trigger are needed to develop schizophrenia
• Meehl's model: gene + stress = schizophrenia
• In the original diathesis-stress model, diathesis was entirely the result of a single 'schizogene'
• Meehl argued that someone without this single 'schizogene' should never develop schizophrenia, no matter how much stress they were exposed to. But a person who does have the gene is vulnerable to the effects of chronic stress. The schizogene is necessary but not sufficient for the development of schizophrenia
• Modern understanding of diathesis:

  It is now believe that diathesis is not due to a single 'schizogene'. Instead it is thought that many genes increase vulnerability

  Also, diathesis doesn't have to be genetic. It could be early psychological trauma affecting brain development

  For example, cild abuse affects the hypothalamic-pituitary adrenal (HPA) system, making a child vulnerable to stress
• Modern understanding of stress:

  A modern definition of stress (in relation to diathesis-stress) includes anything that risks triggering schizophrenia (including psychological stress)

  For example, cannabis use can increase the risk of schizophrenia up to 7 times depending on dose- probably because it interferes with the dopamine system
• Treatment according to interactionist approach:

  Turkington et al. suggest it is possible to believe in biological causes of schizophrenia and still practice CBT to relieve psychological symptoms. But this requires adopting an interactionist model- it is not possible to adopt a purely biological approach, tell patients that their condition is purely biological (no psychological significance to their symtpoms) and then treat them with CBT
• The UK adopts a more interactionist approach compared to the US
• In Britain it is increasingly standard practice to treat patients with a combination of drugs and CBT
• In the US there is more of a conflict between psychological and biological models of schizophrenia and this may have led to slower adoption of the interactionist approach
• Strength:

  Tienari et al. studied children adopted away from schizophrenic mothers. The adoptive parents' parenting styles were assessed and compared with a control group of adoptees with no genetic risk. A child-rearing style with high levels of criticism and conflict and low levels of empathy was implicated in the development of schizophrenia but only for children with a high genetic risk. This is very strong direct support for the interactionist approach- genetic vulnerability and family-related stress combine in the development of schizophrenia
• Limitation: original diathesis-stress model is too simplistic

  Multiple genes increase vulnerability, each with a small effect on its own- there is o schizogene. Stress comes in many forms, including dysfunctional parenting. Researchers now believe stress can also include biological factors. For example, Houston et al. found childhood sexual trauma was a diathesis and cannabis was a trigger. This shows that the old idea of diathesis as illogical and stress as psychological has turned out to be overly simplistic
• Strength: usefulness in treatment

  Tarrier et al. randomly allocated 315 patients to a medication & CBT group, or a medication & supportive counselling group or a control group. Patients in the two combination groups showed lower symptom levels than those in the control group (medication only)- but no difference in hospital readmission. Studies like this show that there is a clear practical advantage to adopting an interactionist approach in the from of superior treatment outcomes
• Limitation: we don't know exactly how diathesis and stress work

  There is strong evidence to suggest that some sort of underlying vulnerability coupled with stress can lead to schizophrenia. But we do not understand the mechanisms by which symptoms of schizophrenia appear and how both vulnerability and stress produce them. This does not undermine support for the approach, but it does mean we have an incomplete understanding of the actual mechanism