Diathesis Stress Model

• Diathesis means vulnerability. Stress in this context refers to negative experiences that may trigger the vulnerability. The diathesis-stress model says a vulnerability and a trigger are needed together to develop schizophrenia. Individually they may not create schizophrenia.
• In the original diathesis stress model, diathesis was entirely the result of a single ‘schizogene‘. Meehl 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 (especially a schizophrenogenic mother). The schizogene is necessary but not sufficient for the development of schizophrenia.
• It is now believed that diathesis is not due to a single 'schizogene. Instead it is thought that many genes increase vulnerability. Also, diathesis doesn't have to be genetic. It could be early psychological trauma affecting brain development. For example, child abuse affects the hypothalamic-pituitary-adrenal (HPA) system, making a child vulnerable to stress.
• A modern definition of stress (in relation to diathesis-stress) includes anything that risks triggering schizophrenia.

  Can be psychological (e.g. parenting) or biological (e.g. cannabis use). Cannabis use can increase the risk of schizophrenia up to seven times depending on dose - probably because it interferes with the dopamine system.