Interactionist approach

• Interactionist approach

  A way to explain the development of behaviour in terms of a range of factors, including both biological and psychological ones. Most importantly such factors don't simply add together but combine in a way that can't be predicted by each one separately i.e. they interact
• Diathesis-stress model

  An interactionist approach to explaining behaviour. For example, schizophrenia is explained as a result of both an underlying vulnerability (diathesis) and a trigger (stressor), both of which are necessary for the onset of schizophrenia. In early versions of the diathesis-stress model, vulnerability was genetic and triggers were psychological. Nowadays both genes and trauma are seen as diatheses and stress can be psychological or biological in nature.
• Interactionist approach (biosocial approach)

  • Acknowledges that there are 3 factors in the development of schizophrenia: Biological factors (genetic vulnerability and neurochemical abnormality), Psychological factors (stress e.g., resulting from life events and daily hassles), and Social factors (such as poor quality interactions in the family).
• Stress

  Negative psychological experiences
• Diathesis-stress model

  Vulnerability + trigger = schizophrenia
• Meehl's diathesis-stress model

  • In the original model, diathesis was entirely the result of a single 'schizogene'. This led to the idea of a biologically based schizotypic personality, one characteristic of this is sensitivity to stress. Meehl 1962 argued that without this gene a person should never develop schizophrenia no matter how much stress they were exposed to. But a person who does have this gene is vulnerable to the effects of chronic stress (e.g., a schizophrenogenic mother), could result in the development of the disorder.
• Modern understanding of diathesis

  • Diathesis is not due to a single 'schizogene' (Ripke et al 2014). Instead it's thought that many genes increase vulnerability. Diathesis does not have to be genetic. It could be early psychological trauma affecting brain development (Ingram and Luxton 2005) – trauma becomes the diathesis rather than the stressor. 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. E.g., the hypothalamic-pituitary-adrenal (HPA) system can become overactive – making person more vulnerable to later stress.
• Modern understanding of stress

  • In the original diathesis-stress model of schizophrenia, stress = psychological in nature (particularly related to parenting). Although psychological stress may still be important, a modern definition of stress (in relation to diathesis-stress) includes anything that risks triggering schizophrenia (including psychological stress and biological factors like cannabis use). Cannabis increases risk of SZ by up to 7 times depending on dose as it interferes with the dopamine system
• Treatment according to the Interactionist approach

  • The model is associated with combining antipsychotic medication and psychological therapies, most commonly CBT. Turkington et al 2006 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 and tell patients that their condition is purely biological (no psychological significance to their symptoms) and then treat them with CBT. In Britain it is increasingly standard practice to treat patients with a combination of CBT and antipsychotics, whereas in the US there is more of a conflict between psychological and biological models of schizophrenia and this may have led to a slower adoption of the interactionist approach.
• One +ve is support for the dual role of vulnerability and stress

  Tienari et al 2004 studied children adopted away from schizophrenic mothers. The adoptive parenting styles were assessed + compared with a C group of adoptees with no genetic risk. A child rearing style with high levels of criticism + 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 + family related stress combine in the development of schizophrenia.
• One limitation is that the original diathesis-stress model is too simplistic

  Multiple genes increase vulnerability, each with a small effect on it own – there is no schizogene. Stress comes in many forms, including dysfunctional parenting.

  Researchers now believe stress can also include biological factors. For example, Houston et al 2008, found that childhood sexual trauma was a diathesis and cannabis use was a trigger. This shows that the old idea of diathesis as biological and stress as psychological has turned out to be overly simple.
• Another strength is the usefulness of the interactionist approach in treatment

  Tarrier et al 2004, randomly allocated 315 patients to (1) medication + CBT group, or (2) a medication + supportive counselling group or (3) a control group. Patients in the two combination groups showed lower symptom levels than those in the control group (medication only). However they found there was no difference in hospital readmissions. Studies like this show that there is a clear advantage to adopting an interactionist approach in the form of superior treatment outcomes.#
• One limitation is 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
• A further limitation is the treatment-causation fallacy

  Turkington et al 2006, argue the fact that combined biological and psychological therapies are most effective than either on their own does not necessarily mean the interactionist approach to schizophrenia is correct. Similarly the fact that drugs help does not mean that schizophrenia is biological in origin. This error of logic is called the treatment-causation fallacy. It means that the superior outcomes of combined therapies should not be over-interpreted in terms of evidence in support of the interactionist approach.