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

In early versions of the model, diathesis was genetic and stressors were psychological.

Genes and trauma are seen as diatheses and stress can be biological or psychological in nature

Meehl’s model

In the original DS 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 a person doesn’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 sufficient for the development of schizophrenia.

Modern understanding of diathesis

It is now clear that 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

In the original DS model stress was seen as psychological in nature.

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

Recent research into factors which might start an episode of schizophrenia has concerned cánnabis use. Cánnabis is a stressor as it increases the risk of schizophrenia 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 interactionist model acknowledges both biological and psychological factors in schizophrenia and is compatible with these treatments. The model combines antipsychotics with psychological therapies like CBT.

Pointed out that it is possible to believe in biological causes and practise CBT. This requires adopting an interactionist model and it is not possible to adopt a purely 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 who assessed family functioning 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.

It is hard to know how much of the 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 there are many factors that 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