Interactionist approach

• The interactionist approach is an approach that acknowledges that there are biological, psychological and social factors in the development of schizophrenia. Biological factors include genetic vulnerability and neurochemical and neurological abnormality. Psychological factors include stress, e.g. from life events and daily hassles, including social factors such as poor quality interactions in the family.
• The diathesis-stress model is an interactionist approach for explaining behaviour. For example schizophrenia is explained as the result of an underlying vulnerability (diathesis) and a trigger (stressor), both of which are necessary for the onset of schizophrenia.
• In the original diathesis-stress model (Meehl) diathesis (vulnerability) was entirely genetic, the result of a single ‘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 does not have the schizogene then no amount of stress would lead to schizophrenia. However, in carriers of the gene, chronic stress through childhood and adolescence, in particular the presence of a schizophrenogenic mother, could result in the development of the disorder.
• One way in which our understanding of distress has changed is that it is now clear that many genes each appear to increase genetic vulnerability only slightly, there is no single ‘schizogene’ (Ripke et al.).
• Modern views of diathesis also include a range of factors beyond the genetic, including psychological trauma-so trauma becomes the diathesis rather than the stressor.
• Read et al. 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 much more vulnerable to later stress.
• In the original diathesis-stress model of schizophrenia, stress was seen as psychological in nature, in particular related to parenting. Although psychological stress, including that resulting from parenting may still be considered important, a modern definition of stress includes anything that risks triggering schizophrenia (Houston et al.).
• Much of the recent research into factors triggering an episode of schizophrenia has concerned cannabis use. In terms of the diathesis-stress model cannabis is a stressor because it increases risk of schizophrenia by up to seven times according to dose, this may be because it interferes with the dopamine system. However, most people don’t develop schizophrenia after smoking cannabis presumably because they lack the requisite vulnerability factors.
• The interactionist model of schizophrenia acknowledges both biological and psychological factors in schizophrenia and is therefore compatible with both biological and psychological treatments. In particular, the model is associated with combining antipsychotic medication and psychological therapies, most commonly CBT.
• Turkington et al. point out that it is perfectly possible to believe in biological causes of schizophrenia and still practice CBT to relieve psychological symptoms. However, this requires adopting an interactionist model- it is not possible to adopt a purely biological approach and tell people diagnosed with schizophrenia that their condition is purely biological and that there is no psychological significance to symptoms, and then to simultaneously treat them with CBT.
• In Britain it is increasingly standard practice to treat people diagnosed with schizophrenia with a combination of antipsychotic drugs and CBT. In the US there is more of a history of conflict between psychological and biological models of schizophrenia and this may have led to slower adoption of an interactionist approach. Thus medication without an accompanying psychological treatment is more common in the US than in the UK.
• A strength of the interactionist approach is evidence supporting the role of both vulnerability and triggers. Tienari et al. investigated the impact of both genetic vulnerability and a psychological trigger (dysfunctional parenting). The study followed 19,000 Finnish children whose biological mothers had been diagnosed schizophrenic(low genetic risk). Adoptive parents had been assessed for child-rearing style and it was found that high levels of criticism, hostility and low levels of empathy were strongly associated with the development of schizophrenia but only in the high genetic risk group.
• Limitation of the diathesis-stress model is oversimplicity. It is clear that the original model that portrayed diathesis as a single schizogene and stress as schizophrenogenic parenting is too simplistic. Multiple genes in multiple combinations influence diathesis. Stress also comes in many forms. In fact diathesis can be influenced by psychological factors and stress can be biological as well as psychological. This is shown in Houston et al.'s study in which childhood sexual abuse emerged as the major influence on underlying vulnerability to schizophrenia and cannabis use as the major trigger
• A further strength of the interactionist approach is the combination of biological and psychological treatments. A practical application of this is the combination of drug treatment and psychological therapies. Studies show combining treatments enhances effectiveness. Tarrier et al. randomly allocated 315 participants to 1) medication + CBT, 2) medication + counselling, or 3) control group (medication only). Participants in the two combination groups showed lower symptoms than the medication-only group, though there was no difference in hospital readmission.