Interactionist approach to explaining Sz (Diathesis-Stress Model)

Diathesis-Stress model

* The interactionist approach is an eclectic approach that suggests schizophrenia can be explained and treated by referring to a combination of biological, psychological and social factors.
* The diathesis-stress model explains that schizophrenia results from an interaction between a vulnerability (diathesis) and an external trigger (stress).

Diathesis

* A VULNERABILTY can predispose the development of schizophrenia.
* e.g. Genetics: The polygenetic explanation suggests a combination of candidate genes (e.g. COMT gene) can leave individuals vulnerable to developing schizophrenia.
* Research: ==Joseph== conducted a ==meta-analysis== of all twin study data prior to 2001. This reported a ==concordance rate of 40% for MZ twin==s compared to @@7% for DZ twins.@@ Since MZ twins are genetically identical (same DNA), the concordance rate is significantly higher than DZ twins and the results from the wide-scale study are likely to have high reliability, this strongly supports the role of genes.
* However, if schizophrenia is purely genetic, a concordance ^^rate of 100%^^ would have been expected for MZ twins. ^^The 60% discordance^^ for MZ twins indicates that ^^stress factors^^ must interact with the biological vulnerability (diathesis) for schizophrenia to develop.

Stress

* Negative experiences can TRIGGER the development of schizophrenia.
* Living in a highly urbanised environment: The more adverse living conditions of a densely populated urban environment may act a contributory trigger.
* Research: ==A meta-analysis by Vassos et al.== found that the risk for schizophrenia in the most urban environments was estimated to be over t==wice as likely than in the most rural environments==.
* However, despite many people living in such areas, only a ^^tiny minority develop schizophrenia.^^ Therefore, the development of schizophrenia may be ^^conditional on this stress factor^^ interacting with a pre-existing diathesis factor.

Evaluation of interactionist approach to explaining SZ: ==research support (Tienari)==

* ==Tienari et al== investigated the combination of ==genetic vulnerability (diathesis factor) and parental child-rearing style (stress factor)==.
* They compared the rates of schizophrenia of ==children adopted== between 1960 and 1979 from Fi==nnish mothers with schizophrenic symptoms (high risk)== to a @@matched control group of adoptees with mothers without schizophrenic symptoms (low risk)@@.
* The adoptees were assessed at around ==12 years and 21 years== and adopted family functioning was measured using a ==family rating scale== based on interviews and observations covering aspects such as conflict, empathy and insecurity.
* Adoptive-family ratings predicted schizophrenia, but only in ==adoptees with a high genetic risk== and not in adoptees with low genetic risk.
* This supports the importance of using an interactionist approach to explaining schizophrenia as it suggests that the contribution of ==both a genetic vulnerability (diathesis) and family dysfunction (stress)== are important in the development of schizophrenia.

Evaluation of interactionist approach to explaining Sz: ^^revised understanding of diathesis^^

* The original diathesis-stress model for schizophrenia ^^over-emphasises vulnerability^^ in terms of genetic influences. Other ^^non-genetic diatheses may also predispose an individual^^ to develop schizophrenia.
* For example, a baby may incur ^^brain damage during a problematic childbirth^^ which is an environmental factor can make a child vulnerable to developing schizophrenia.
* ^^Verdoux et al.^^ estimated that the risk of developing schizophrenia later in life for individuals who experienced ^^obstetric complications^^ at birth (e.g. ^^prolonged labour^^ which can cause oxygen deprivation) is ^^four times greater^^ than those who experience no such complications.
* Modern diathesis-stress models support the interactionist explanation of schizophrenia, but suggest ^^internal vulnerabilities^^ ^^may be structural^^ or ^^functional^^ rather than only genetic.

Evaluation of interactionist explanation of Sz: ^^revised understanding of stress^^

* The original model for schizophrenia assumed that stress factors which trigger schizophrenia involve ^^negative psychological experiences,^^ such as living in a highly urbanised environment.
* However, ^^other risk factors linked to biology^^ may also be involved. Many recent studies into risk factors triggering schizophrenia focus on ^^cannabis use^^, as this interferes with the ^^dopamine system,^^ which has been linked to hallucinations experienced in psychosis.
* For example, ^^Andréasson et al^^ reported results of a 1^^5-year longitudinal study of 45,570 male conscripts^^ in Sweden and found the ^^heaviest users of cannabis^^ (more than 50 occasions) had ^^6 times the risk^^ of developing schizophrenia compared with non-users.
* It is important to note, however, that research into risk factors is ^^often correlational so causality cannot be inferred^^ and it is likely that a combination of risk factors is involved.

Evaluation of interactionist explanation of Sz: ==allows for free-will==

* The diathesis-stress model accepts that i==nternal factors such genetic predispositions play a part== in schizophrenia, but explains that this only makes a person vulnerable to developing the disorder.
* This has ==positive implications== for an individual with ==closely-related family members== with schizophrenia because they would recognise that genetic factors alone do not biologically determine that they will develop the disorder.
* Knowledge that their genetic vulnerability requires an external trigger enables the individual to ==make positive life choices==, such as ==avoiding highly urbanised environments and cannabis use==, which can mitigate the development of schizophrenia or going to therapy when first signs of symptoms show