The biological approach (or the medical model) is based on the view that psychological disorders can be explained in the same way as physical disorders, i.e. they are manifestations of an underlying biochemical or physiological dysfunction, which may or may not have a known cause. The biological approach is also called the medical model because it is based on the idea of diagnosing physical symptoms and providing appropriate treatments, as is done with physical illness.
- Genetic transmission – Mental illness is the result of an inherited gene or group of genes. Evidence comes from twin or family studies. For example, Gottesman and Shields (1972) found that concordance rates for schizophrenia in non-identical twins is about 9%, whereas it rises to 42% in identical twins, indicating some environmental influence, but a larger genetic component for the disorder. A ‘concordance rate’ is the extent to which two things are related, in this case how frequently both twins have the same disorder. Other studies have used gene-mapping to demonstrate the location of the actual gene(s) that cause the disorder. For example, Meyer et al. (2001) found that a mutation in the gene WKL1 showed up in seven family members with a particular form of schizophrenia, but not in six others who had no symptoms of the disorder.
- Biochemical abnormalities – Many studies have found abnormal levels of certain neurotransmitters and/or hormones. For example, depression has been linked to low levels of noradrenaline and serotonin, and schizophrenia has been linked to high levels of dopamine. Some forms of depression are related to disordered hormone levels, such as post-partum depression and pre-menstrual syndrome. Abnormal brain chemistry may be the result of faulty genes – Meyer et al. propose that the unusual form of WKL1 found in some schizophrenics may cause abnormal protein production. Or, abnormal brain chemistry could be the effect of mental illness. Either way, the use of drugs to return neurotransmitters or hormones to normal levels has been shown to be effective. The medical approach involves the diagnosis of syndromes (or diseases) by identifying symptoms and then deciding on appropriate treatment. The medical model involves the use of classification systems, such as DSM (Diagnostic and Statistical Manual of Mental Disorders) in which each mental disorder is given a list of typical symptoms to help diagnose mental illness. DSM is used in America, whereas ICD (International Classification of Diseases) is used in the UK and Europe.
- Neuroanatomy – The structure of the brain has sometimes been found to be different in people with certain mental disorders. For example, Chua and McKenna (1995) reported that the brains of schizophrenic patients were smaller and had larger ventricles than the brains of normal individuals.
- Infection – Mental disorders may be caused by a virus or bacteria. For example, general paresis was regarded since the 16th Century as a mental illness, but has since been found to be caused by the syphilis bacterium. Crow (1984) proposed that schizophrenia is caused by a retrovirus, which becomes incorporated into DNA.
Strengths:
- The medical treatment of insanity was a move in the direction of humaneness. The illness, rather than the patient, was blamed. On the other hand, control is taken away from the patient, who relies on expert guidance. The medical model is the
dominant model for explaining and treating mental illness. It tends to be favoured by psychiatrists, whereas clinical psychologists favour psychological models.
- At least some disorders have a biological basis. However, an exclusive emphasis on biological bases may mean that other factors are overlooked.
Weaknesses:
- In many cases, it is not clear whether the physical factor is actually an effect rather than a cause.
- The medical model may be appropriate for physical illness, but not for mental illness where symptoms are less objective. It overlooks the fact that mental disturbance is often defined in terms of social difficulties. In fact, Clare (1980) pointed out that many physical illnesses also have a social-psychological component and, therefore, the medical model may be insufficient on its own even for physical illnesses.
- The medical approach may prevent us understanding the true causes of mental disorders. Szasz (1960) argued in his book The Myth of Mental Illness that the medical model is ‘worthless and misleading’ and ‘scientifically crippling’. He claimed that it is a modern day version of demonology and serves the same political purposes, namely social control, by those invested with undisputed authority – the medical profession.
- The medical approach purports to be value-free and scientific, but is just as subject to prevailing attitudes as other models.
A combined approach: The diathesis–stress model
It may be more realistic to combine the biological and psychological models. Mental illness arises when both factors combine:
- Diathesis: a genetic vulnerability or predisposition.
- Stress: some environmental event that triggers the predisposition.
The diathesis–stress model explains why, when one identical twin develops a disorder, their twin does not always develop the disorder –
because they do not both experience the same environmental triggers. It also explains why people who share certain traumatic experiences do not all develop, for example, depression – because some people are more vulnerable to develop depression.
PROGRESS CHECK
- Identify one key feature of the biological approach.
- Would you expect identical or non-identical twins to have a higher concordance rate for schizophrenia?
- Identify one similarity between mental and physical illnesses.
- What is the diathesis–stress model?
