interactionist approach

• The diathesis stress model

  • diathesis means vulnerability
  • stress refers to negative experiences that trigger vulnerability
  • the diathesis stress model says both a vulnerability and a trigger are needed to develop schizophrenia - it is the interaction that is key
• meehls model - diathesis is genetic

  • in the original diathesis stress model, diathesis was entirely the result of a single schizogene
  • meehl (1962) argued that someone without this gene 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 e.g schizophrenogenic mother
  • the schizogene is necessary but not sufficient for the development of schizophrenia
• modern understanding of diathesis

  • its now believed that diathesis is not due to a single schizogene
  • instead, its thought that many genes could increase vulnerability
  • diathesis doesnt have to be genetic, it could be early psychological trauma affecting brain development
• modern understanding of stress

  • a modern definition of stress includes anything that risks triggering schizophrenia
  • stress can be psychological e.g. parenting or biological e.g. cannabis use
  • cannabis use can increase the risk of schizophrenia up to 7x depending on the dose - probably because it interferes with the dopamine system
• treatment according to the interactionist model

  • antipsychotic drugs can be taken in combination with CBT. this requires adopting an interactionist model - its not possible to adopt a purely biological approach, tell patients that their condition is purely biological and then treat them with CBT (Turkington 2006)
  • In Britain its 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 appraoch
• one strength is support for the dual role of vulnerability and stress

  Tienari (2004) studied children away from mothers diagnosed with schizophrenia. 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 shows that a combination of genetic vulnerability and family stress leads to increased risk of schizophrenia
• one limitation of the original diathesis stress model is it’s over simplistic 


  multiple genes increase vulnerability, each with a small effect on its own - there is no schizogene. stress comes in many forms, including dysfunctional parenting. researchers now believe stress can also include biological factors. for exmaple, Houston (2008) found childhood sexual trauma was a diathesis and cannabis use was a trigger. this means that there are multiple factors, biological and psychological affecting both diathesis and stress
• another strength is real world application of interaction

  Tarrier (2004) randomly allocated 315 participants to 1) medication + CBT group, or 2) medication and supportive counselling group, or 3) control group (medication only). participants in the 2 combination groups showed lower symptom levels than those in the control group - bit no difference in hospital readmission. this means that there is a clear practical advantage to adopting an interactionist approach in the form of superior treatment outcomes.
• another strength is real world application of interaction: counterpoint 


  however, Jarvis and Okami (2019) suggest this argument is the same as claiming that beause alcohol reduces shyness, that shyness is caused by a lack of alcohol, the treatment causation fallacy. therefore, we cannot automatically assume that the ssuccess of combined therapies means interactions t explanations are correct.