The interactionist approach to schizophrenia

Interactionist approach

A way to explain the development of behaviour in terms of a range of factors, including biological and psychological ones.

Factors don’t add together but combine in a way that can’t be predicted by each one separately

Diathesis-stress model (DS)

An interactionist approach to explaining behaviour.

Schizophrenia is the result of an underlying vulnerability (diathesis) and a precipitating factor (stressor), which are both necessary for the onset of schizophrenia.

In earlier versions, diathesis was genetic and stressors were psychological. Now both can be seen as biological or psychological.

Meehl’s model

In the original model diathesis was genetic, the result of a ‘schizogene’. Led to the idea of a biologically-based schizotypic personality - 1 characteristic which is sensitivity to stress.

If you don’t have the schizogene then no amount of stress would lead to schizophrenia.

In carriers of the gene, chronic stress through childhood can result in the development of the condition. The schizogene is necessary but not enough for the development of schizophrenia.

Modern understanding of diathesis

Many genes increase genetic vulnerability. The diathesis part can also be the stressor.

Read proposed a neurodevelopmental model where early trauma affects the developing brain.

Early and severe enough trauma can seriously affect many aspects of brain development. The HPA system can become overactive and makes someone more vulnerable to later stress.

Modern understanding of stress

Stress was seen as psychological in nature.

Although stress including that resulting from parenting may be important, a modern definition of stress includes anything that risks starting schizophrenia.

Recent research into factors which might start an episode of schizophrenia concerned cánnabis use. It is a stressor as it increases the risk up to x7 according to dose as it affects the dopamine system.

Most people do not develop schizophrenia after using cánnabis as they lack vulnerability factors.

Treatment according to the interactionist model

Turkington

The model acknowledges biological and psychological factors in schizophrenia and is compatible with these treatments. Combines antipsychotics with psychological therapies like CBT.

Pointed out that you can believe in biological causes and practice CBT. Requires adopting an interactionist model so it is not possible to have a fully biological approach.

S Tienari

Evidence to support the role of diathesis and stressors.

Investigated genetic diathesis and psychological stressors in 19,000 Finnish children whose biological mothers had schizophrenia.

High-risk genetic group compared to a control group of adoptees with no family history of schizophrenia.

Adoptive parents were assessed for child-rearing style. High criticism, hostility and low empathy were associated with the development of schizophrenia only in the high risk group.

Supports the view that a combination of genetic vulnerability and family stress can lead to increased risk of schizophrenia.

W Methodological criticism of Tienari

The psychiatrists used a rating scale at 1 point. Measured aspects like lack of empathy and parent-child conflict. This may not give an accurate representation of the developmental changes over time.

Hard to know how much stress was caused by the adoptee or family. So the child may be instigating the stress rather than the family creating a stressful environment.

The conclusion that adoptive-family stress is a predictor of schizophrenia is invalid.

W Oversimplicity of diathesis-stress model

Original model saw diathesis as a single schizogene and stress as schizophrenogenic parenting. Multiple genes in combinations influence diathesis. Stress can also come in many forms.

Diathesis can be influenced by psychological factors and stress can be both biological and psychological

Houston showed that childhood séxual abuse was seen as the major influence on diathesis to schizophrenia and cánnabis use as the major stressor.

Suggests that many factors affect both diathesis and stress and supports the modern understanding of both.

S Tarrier

Practical application of the combination of biological and psychological treatments.

Randomly allocated 315 participants to medication + CBT, medication + counselling or medication only.

Participants in the combination groups showed better outcomes after the trial compared to the medication only group. There was no difference in hospital readmission.

There is a clear practical advantage to adopting an interactionist approach to treating schizophrenia