diathesis stress model for schizophrenia

diathesis-stress model

originally proposed by meehl in 1962, this model proposes that both a vulnerability to schizophrenia and a stress-trigger are necessary to develop the condition.

old model

- vulnerability is genetic, the result of a singular 'schizogene'

- causes a sensitive personality

- chronic environmental stress, such as having a schizophrenogenic mother, results in the onset of schizophrenia

- individuals without the 'schizogene' cannot develop schizophrenia, no matter how stressful their upbringing

diathesis factors

- genetic factors

- exposure to flu virus during gestation can altar development of nervous system

- birth complications can altar CNS

stress factors

- trauma, e.g. abuse/eglect

- parenting style

- exposure to particular chemicals, e.g. cannabis

modern model

- many genes increase genetic vulnerability

- range of factors beyond genetic, including psychological trauma - trauma becomes the diathesis, rather than stressor

- read (2001) proposed neurodevelopmental model in which traumas during early development alters the developing brain

- broader definition of stress has been adopted and refers to anything that risks triggering schizophrenia

evaluation

- one strength of this model is that there is research support. tierani (2004) investigated combinations of genetic vulnerability and parenting styles. children adopted from 19 000 Finnish mothers with schizophrenia between 1960-1979. adoptive parents were assessed for child-rearing styles and the rates of schizophrenia in the children were compared to those in a control group of adoptees without any genetic risk. they found that a child-rearing style of high levels of criticism and conflict and low levels of empathy were implicated in the development of schizophrenia, but only for children in the high genetic risk group. this suggests that both genetic vulnerability and family stress are important in the development of schizophrenia.

- one limitation of this model, however, is that it is not precise. it proposes that schizophrenia is caused by a combination of biology and environment. however, it is not known precisely how these risk factors - i.e. how biological, environmental, psychological and social factors - contribute to the diathesis-stress interaction, as the causes may differ between individual schizophrenic patients. this weakens this model as the mechanisms by which the illness develops and how both vulnerability and stress produce it.

- another limitation is that critics have argued that the original diathesis-stress model is over simplistic. for example, the idea that a single gene combined with a certain parenting style causes the schizophrenia is too simplistic. multiple genes have been found to increase the risk of developing the illness indicating that there is no single 'schizogene'. also, stress is not limited to just parenting style and family dynamics. more recent research by houston et al. (2008) found that vulnerability is not limited to biology by finding that childhood sexual trauma increased