Interactionist explanation for SZ

What is the interactionist approach?

An explanation of behaviour that combines biological and psychological factors, emphasising that they interact rather than simply add together

What is the diathesis‑stress model?

An interactionist explanation suggesting schizophrenia results from a vulnerability (diathesis) combined with a trigger (stress) - both are needed for SZ to occur

What was the traditional view of diathesis and stress?

Vulnerability was genetic, and stress was psychological

What is the modern view of diathesis and stress?

Both genes and trauma can be diatheses, and stress can be psychological or biological

What did Meehl argue the diathesis (vulnerability) was in his original model?

Entirely genetic — caused by a single “schizogene.” (linked to SZ)

According to Meehl, can someone without the schizogene develop schizophrenia?

No - no amount of stress would trigger schizophrenia without the schizogene

What type of stress did Meehl believe could trigger schizophrenia?

Chronic stress such as childhood or adolescent trauma (e.g., a schizophrenogenic mother) (if you had the gene)

What is the modern view of genetic vulnerability?

Many genes are implicated - vulnerability is polygenic

How can diathesis be psychological?

Psychological trauma can alter brain development (e.g., Read’s neurodevelopmental model)

What counts as a stressor in the modern model?

Anything that increases the risk of triggering schizophrenia

How does cannabis act as a stressor?

It increases the risk of schizophrenia up to sevenfold, likely due to its effects on the dopamine system

What does the interactionist model imply about treatment?

Treatment should combine biological and psychological methods

What treatment combination is typically used?

Antipsychotic medication + CBT or family therapy

What does Turkington et al. (2006) argue?

Someone may have a biological cause of schizophrenia but can still benefit from psychological therapies like CBT

What is standard practice in the UK for treating schizophrenia?

A combined approach using both medication and psychological therapy - biological treatments can allow the patient to reduce their symptoms so they can engage with psychological therapies

How does the US differ in treatment practice?

Medication‑only treatment is more common due to a historical divide between biological and psychological approaches

How is the fact that there is strong research evidence showing that both biological vulnerability and environmental stress are needed for schizophrenia to develop a strength?

because it clearly demonstrates the diathesis–stress model: genetic vulnerability alone is not enough, and environmental stress alone is not enough - schizophrenia emerges when the two interact.

Give an example of this strength

For example, Tienari et al. studied over 19,000 Finnish adoptees and found that children with a biological mother diagnosed with schizophrenia were more likely to develop the disorder - but only if their adoptive families showed high levels of criticism, hostility, or low empathy. Children without the genetic vulnerability did not develop schizophrenia, even in the same adverse environments

Combined treatments are shown to be more effective than biological treatments alone. How is this a strength?

because it demonstrates that addressing both biological and psychological factors leads to better clinical outcomes.

Give an example of this strength

For example, Tarrier et al. randomly allocated 315 patients to three groups: medication + CBT, medication + counselling, or medication only. Both combination groups showed lower symptom severity than the medication‑only group, even though hospital readmission rates were similar

How is the fact that it can be difficult to identify the exact environmental stressors that trigger SZ a limitation of the interactionist explanation?

because it makes it difficult to predict who will develop SZ and when the disorder will occur, reducing the explanatory power of this diathesis-stress model

Give an example of this limitation

for example, individuals with the same genetic vulnerability may experience different life events but not all of them develop SZ

How is the fact that the interactionist approach highlights the importance of early intervention and prevention a further strength?

because it suggests that SZ may not be inevitable for those with the genetic risk and that environmental change or support could help prevent the disorder

Give an example of this strength

for instance, if individuals who have a biological vulnerability are identified early, reducing environmental stressors or providing psychological support may reduce the likelihood of SZ developing