Diathesis-Stress interactionist approach Flashcards
What is the diathesis-stress model?
- Sees schizophrenia as the result of an interaction between biological (diathesis) and environmental (stress) influences.
- Whether or not a person develops the condition is partly determined by genetic vulnerability, and amount of stresses they experience over their lifetime.
What is the diathesis (biological) element?
- States schizophrenia has a genetic component
- Genetic role is supported by twin studies - an identical twin of a person with schizophrenia is at greater risk than sibling or fraternal twin.
- Adoptive relatives do not share the increased risk of biological relatives - concordance rate isn’t 100% which suggests other factors must also be at play.
What is the stress (environmental) element?
States stressful events can trigger the condition, can take a variety of forms such as:
Childhood trauma:
- Varese found children who experienced severe trauma before 16 were 3x likely to develop condition compared to general
- There was a relationship between level of trauma and likelihood of developing with those severely traumatised as children more at risk.
Cannabis:
- Lot of research concerning use of cannabis into triggering an episode
- Cannabis = stressor as increases risk x7 depending on dose and usage.
- Most do not develop after smoking cannabis so seems there must be more factors
What is the diathesis-stress combined?
Several ways a combination can lead to onset of disorder e.g:
- relatively minor stressors for an individual highly vulnerable
- major stressful event for a person low in vulnerability.
Whatever the combination, this idea pre-supposes additivity, i.e. diathesis and stress add together in some way to produce schizophrenia.
What are 2 strengths of the diathesis-stress model?
Supported by Tienari’s 2004 study:
- Tested hypothesis that genetic factors coupled with poor family environment can increase likelihood
- Hospital records of nearly 20,000 women at Finnish psychiatric hospitals 1960-79, identifying those diagnosed at least once with schizophrenia or paranoid psychoses
- Found some whose offspring was taken away
- Resulting sample of 145 adopted-away offspring (high-risk) matched with sample of 158 adoptees without genetic risk (low-risk)
- Both groups assessed after 12 and 21 years
- Tienari et al found of 303 adoptees, 14 developed schizophrenia
- 11 of these were the high risk group - suggests a strong genetic link
- Being reared in a healthy adoptive family appeared to have protective effect even for those high risk.
- High risk adoptees in families with good functioning were significantly less likely to develop condition than high genetic risk in family with poor functioning.
These findings support model by suggesting certain individuals are predisposed to condition through genes, and the suffering from the condition is increased or decreased by the environment they grow up in.
Has practical applications:
- Acknowledges both biological + psychological factors - lends itself to a combined approach
- Associated with combining antipsychotics with psychological therapies, mainly CBT
- In Britain its increasingly standard practice to treat with a combination
- In USA there is more conflict between treatments, led to slower adoption of this approach
- Therefore, its unusual in the UK to treat schizophrenia with only one treatment.
- CBT, family therapy + token economies usually carried out with antipsychotics
This combined approach would seem to suggest that schizophrenia can be explained by a combination of both biological and psychological factors thus supporting the model
What is a limitation of the diathesis-stress model?
Original diathesis-stress model is over-simplified:
- Assumed a single gene and a single environmental trigger combined to explain schizophrenia.
- However there isn’t one single schizophrenic gene or single environmental trigger - stress can come in many forms
- It is also believed that the diathesis element does not have to be biological
- James Houston’s study showed that childhood sexual trauma emerged as a vulnerability factor whilst cannabis acted as a trigger.
This shows that the old diathesis as biological or stress as psychological has turned out to be overly simple, which is a problem for the old model, but not for more recent models.
