Interactionist approach to Sz

• Interactionist approach


  also known as the biosocial approach, is a way of explaining behaviour in terms of a range of factors, including both biological and psychological ones. It looks at how they combine in a way that can't be predicted by each one separately as they interact.
• The diathesis-stress model


  The diathesis-stress model says that both a vulnerability to schizophrenia and a stress trigger are necessary to develop the condition. One or more underlying factors make a person particularly vulnerable to developing Sz but the onset is triggered by stress.
• Meehl's Model


  The original (1962) diathesis-stress model was entirely genetic, resulting from a 'schizogene'. This led to the idea of a biologically based schizotypic personality, one characteristic of which is sensitivity to stress. According to Meehl, if a person doesn't have the gene, then no amount of stress can cause them to develop Sz. However, if a person carries the gene, chronic stress through childhood and adolescence, in particular the presence of a schizophrenogenic mother, could develop the condition.
• Modern understanding of diathesis (vulnerability)


  It is now clear it is polygenic, many genes each appear to increase vulnerability only slightly. Modern views include psychological trauma. Read et al. (2001) proposed a neurodevelopmental model in which early trauma alters the developing brain. Early and severe enough trauma, such as child abuse, can seriously affect many aspects of brain development. For example, the hypothalamic-pituitary-adrenal (HPA) system can become overactive, making a person later more vulnerable to stress.
• Modern understanding of stress


  The modern definition of stress (concerning the diathesis-stress model) includes anything that risks triggering Sz. Recent research has been concerned with cannabis use, it is considered a stressor as in increases the risk of Sz by up to seven times according to dose. This may be because it interferes with the dopamine system. However, most people do not develop Sz after smoking cannabis, presumably because they don't have the vulnerability factors.
• Interactionist Approach treatment in the UK

  In Britain, it is increasingly standard practice to treat patients with a combination of antipsychotics and CBT. In the US there is more of a history of conflict between psychological and biological models of SZ which may have led to the slower adoption of an interactionist approach. This medication without an accompanying psychological treatment is more common in US than UK.
• Treatment according to the interactionist model


  The model is associated with combining antipsychotic medication with psychological therapies, most commonly CBT.

  • Douglas Turkington et al. (2006) pointed out it is perfectly possible to believe in biological causes of Sz and still practice CBT to relieve psychological symptoms. However, this required adopting the interactionist model- it is not possible to adopt the purely biological approach and tell patients to get treated with CBT while telling them there is no psychological significance to symptoms.
• Limitation of the original diathesis-stress model


  Oversimplified. Multiple genes and combinations of genes effect diathesis. Stress comes in many forms. Diathesis can be influenced by psychological factors and stress can be influenced by biological factors. Houston et al. (2008) found childhood sexual abuse emerged as a major underlying vulnerability to Sz and cannabis as the major trigger. This means there is multiple factors, psychological and biological, affecting both diathesis and stress, supporting modern understandings
• Strength of the interactionist approach


  Evidence supporting the role of vulnerability and triggers. For example, Tienari et al. (2004) in a large-scale study of 19,000 Finnish children with mothers with Sz compared to a control group of adoptees. He found being brought up with high levels of criticism, hostility and lack of empathy was strongly associated with Sz, only in the genetically vulnerable. This shows a combination of genetic vulnerability and family stress increases the risk of Sz.
• Strength of the interactionist approach application


  Studies show combining psychological and drug treatments enhances effectiveness. Tarrier et al. (2004) randomly allocated 315 participants to 3 conditions, meds + CBT, meds+ counselling, control (meds only). Participants in the combination groups showed lower symptoms after the trial, though hospital readmissions were the same. This means there is a clear practical advantage to the interactional approach in terms of treatment outcome.
• Counterpoint to interactionalist applicability


  Jarvis and Okami (2019) pointed out saying a successful treatment of a mental disorder justifies an explanation is illogical. This logical error is called treatment-causation fallacy. For example, when using one treatment such as drugs, if symptoms are reduced, it is assumed that the cause is biological. Therefore we cannot automatically assume that the success of combined therapies means the interactionist approach is correct.
• Urbanisation to evaluate the interactionist approach


  Sz is more commonly diagnosed in urban than rural areas. The statistic is sometimes used to justify the interactionist position, as it assumes that urban living is more stressful than rural and therefore city living acts more as a trigger.

      However, it may simply be that Sz is more likely to be diagnosed in cities, or people with a diathesis for schizophrenia tend to migrate to cities.