Lesson 6 - Diathesis-Stress model

Question 1

What is the interactionist approach?

Answer 1

AKA the biosocial approach

• Acknowledges the biological, psychological and societal factors in the development of SZ.
• eg. genetic factors, dopamine, stress, grief, daily hassles and insecurities or poor family life

Question 2

The diathesis-stress model

Answer 2

Diathesis = vulnerability

Vulnerability + stress trigger = SZ

Meehl (1962) –Originally thought to be due to one gene (the schizogene) leading to a schizotypic personality, and if you did not have this, no amount of stress could trigger it. However if you did, then chronic stress triggers like the schizophrenogenic mother would trigger SZ.

More modern approaches now understand that SZ is polygenic. Also takes into account genes but also traumas as the original vulnerability factor, so trauma can mean more vulnerable to stress and then as a result = SZ. (Read et al, 2001)

Question 3

Read et al (2001)

Answer 3

Proposed a neurodevelopment mode, in which traumas that can originate in childhood such as child abuse can cause overactivity in some areas of the brain like the hypothalamic pituitary adrenal system (HPA) which can cause vulnerability to stress.

Question 4

Treatment according to the interactionist/biosocial model

Answer 4

As this approach accounts for both the biological and psychological factors in developing SZ, it is increasingly standard practice in the UK to treat Sz with both drugs and CBT. It is unusual to treat SZ with psychological therapies alone because it is such a complex disorder. Drugs are administered to control the symptoms and FT or CBT will be administered too

Question 5

Strengths of the interactionist approach

Answer 5

• Evidence for the role of vulnerability and triggers –there is research support for the role of genetic vulnerability to SZ and stress triggers. Tienari et al (2004) (1994 study also used in the evaluation for family dysfunction, basically same study) found that adoptees with SZ biological parents who were adopted by families judges to be critical and conflicting were implicated in the development of SZ but only for children with high genetic risk. Supports the idea of both psychological theories, like family dysfunction but also genetics
• Supports the effectiveness of the combination of treatments –another strength is the usefulness of the interactionist approach in the treatment of SZ. Tarrier et al (2004) randomly allocated 315 patients to:

1. medication + CBT
2. medication and support counselling group
3. control group (med only)

Patients in the combo groups (1 and 2) showed lower symptom levels than those who only took meds.

Question 6

Weaknesses of the interactionist model

Answer 6

• The original model of diathesis-stress is too simplistic –multiple genes increase vulnerability, each holding its own small effect, so unlike what Meehl (1962) stated, there is no ‘schizogene’. Also, recent research has found that biological factors can be triggers, not just vulnerabilities. Houston et al (2008) found that childhood sexual trauma (diathesis) was triggered by cannabis. This shows that the old idea of diathesis = biological and trigger = psychological is reductionist
• We do not understand the mechanisms by which symptoms appear and how both vulnerability and stress directly interact to produce them. While this does not undermine the myriad of evidence suggesting a link, but it means that more research needs to be done to figure out what exactly happens when the two factors interact.
• Treatment-Causation Fallacy – Turkington et al (2006) argued that the fact that interactionist treatments are more effective does not mean that the interactionist approach is correct, so just because of the effectiveness of drug therapies does not necessarily mean we can deduce that SZ is biological in nature. Both the cause and treatment of SZ should be taken with caution and we should not assume that effectiveness = cause