Interactionist Approach - Diathesis-Stress Model

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The Diathesis-Stress Model

The diathesis-stress model is a major component of the interactionist approach. It was originally developed by Meehl in 1962.

The interactionist (or biosocial) approach acknowledges that there are biological, psychological, and societal factors in the development of schizophrenia.
Biological factors include genetic vulnerability, and neurochemical and neurological abnormality.
Psychological factors include stress, potentially resulting from life events and daily hassles, including poor quality interactions in the family.

A major part of the interactionist approach is the diathesis-stress model, originally developed by Meehl (1962). The theory has since been revised to take into account advances in genetics.
Diathesis means vulnerability, and in the case of schizophrenia applies to negative psychological experiences.
According to the diathesis-stress model, vulnerability to schizophrenia and a stress-trigger are necessary for the condition to develop.

In Meehl’s original model, diathesis was entirely genetic. Diathesis was the result of a single ‘schizogene’, which led to the development of a biologically based schizotypal personality.
One characteristic of this was a sensitivity to distress.
According to Meehl, people without the schizogene will not develop schizophrenia, regardless of levels of stress.
But the presence of a schizophrenogenic mother could result in the development of the condition if the schizogene was present.

Modern interpretations of diathesis-stress take into account the current understanding that many genes are involved in the development of schizophrenia and there is no single schizogene.
Instead, the current version of the model acknowledges a range of factors beyond genetics (such as psychological trauma) which lead to the trauma becoming the diathesis rather than the stressor.

Vulnerability and stress do not have one single source, as the original diathesis-stress model suggested.

Studies like Tienari et al (2004) have helped psychologists see how the original diathesis-stress model is too simple, especially regarding the idea of a single schizogene and schizophrenic parenting style.

It is now understood that multiple genes increase vulnerability to schizophrenia, each having a small effect on its own.
Stress is no longer believed to be limited to dysfunctional parenting.
Instead, it is now accepted that vulnerability can be the result of early trauma as well as genetic make-up, and that stress can come in many forms including biological.

In a recent study by Houston et al. (2008), childhood sexual trauma emerged as a vulnerability factor while cannabis use was a trigger.
This shows that the old idea of diathesis as biological and stress as psychological is overly simple.
This is a problem with the older form of the diathesis-stress model, but not the new version.