Abnormality is caused by physical factors
The biological model assumes all mental health disorders are related to change in the body like a physical disorders.
These changes may be caused by:
- Viral infection
Abnormalities in the brain anatomy or chemistry can be the result of genetic inheritance.
This can be studied by using identical twins to see whether if one of them has a disorder the other has it as well providing us with a concordance rate, the extent to which 2 individuals are similar to each other.
Genes responsible for abnormal behaviour are a product of evolutionary adaptations in our ancestors.
Certain genes lead to abnormal biochemistry and/or
Genes tell the body how to function controlling neurotransmitters and hormones and neuroanatomy.
High levels of serotonin a neurotransmitter are associated with anxiety whereas low levels have been found in depressed individuals.
Schizophrenics are thought to have spaces in their brains indicating shrinkage of brain tissue.
Schizophrenia may be related to exposure to certain viruses in the womb.
Torrey: mothers of many people with schizophrenia had contracted a particular strain of influenza during pregnancy. The virus may have entered the unborn child's brain where it remains dormant until puberty when other hormones may activate it, producing the symptoms of schizophrenia.
Humane or inhumane?
The emergence of medical model led to more humane treatment for mental patients as previously it was blamed on demons r evil in the individual.
The medical model offered a different blame the illness was potentially treatable. However the medical model is criticised for being inhumane, mental illness did not have a physical basis therefore shouldn't be thought of in the same way.
Cause and effect?
The available evidence doesn't support a simple cause and effect link between mental illness such as schizophrenia and altered brain chemistry.
Schizophrenia is commonly associated with brain neurotransmitter dopamine although some studies have shown schizophrenics with low levels of dopamine in some brain tissues meaning there may be simultaneous excesses and deficiencies in different parts of the brain.
There is no evidence that mental disorders are purely caused by genetic inheritance- concordance rates are never 100%.
Gottesman and Shields reviewed the results of 5 studies of twins looking for concordance rates for schizophrenia. They found that in genetically identical twins there was a concordance of 50%. If schizophrenia was entirely produced by genetic inheritance we might expect the figure to be 100%.
Certain disorders, what individuals inherit is a susceptibility for the disorder but the disorder itself only develops if the individual is exposed to stressful life conditions (diathesis-stress model).
Methods of Investigating the biological approach
Experiments: if patients fare better with drugs which alter the brain chemistry this outcome is taken to show the importance of biochemical changes in that disorder.
Correlational studies: because it is impractical to carry out experiments to test for genetic inheritance, psychologists rely on correlations to investigate the relationship between heredity and the development of mental disorders. Correlational studies provide a comparison of the frequencies of mental disorders in various populations but do not demonstrate cause and effect.