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4) The Biological Model

The biological model is based upon the assumption that abnormality is due to biological imperfections in the body. There are 4 main biological differences that can cause an abnormality, genetic inheritance, chemical imbalance, brain injury and viral infections.

Genetic inheritance

This is the genes we inherited at birth. They can sometimes be faulty, causing abnormalities.

We have used twins in studies to find out if an abnormality is caused by genetic inheritance. Monozygotic (identical twins) will have the same genes, so if one twin has an abnormality, but the other doesn’t it can’t be due to abnormality. However, if both have the same abnormality it is likely to be caused by genetic inheritance.

Gottesman’s meta-analysis of 40 “twin-studies” into Schizophrenia and found that the concordance rate of Schizophrenia for MZ twins was 48%. This means that almost half of the abnormalities these twins had were almost definitely caused by genetic inheritance. He also found dizygotic twins had a concordance of only 17%, proving again that genetic inheritance can cause abnormality.

Chemical Imbalance

If an individual has incorrect levels of a certain chemical, the person may suffer from an abnormality. For example low levels of Serotonin have been proven to cause depression, and high levels of dopamine are thought to cause Schizophrenia.

A chemical imbalance could be caused by a change in environment, or through genetic inheritance. For example, you could inherit a problem which causes low levels of a certain chemical.

Viral Infection

Some research has suggested that viral infections can cause biological differences in the brain resulting in abnormality. For example research says Schizophrenia can be related to certain viruses, i.e. influenza, in the womb.

Similarly an infection in later life could cause abnormality. For instance, Syphilis has been shown to cause some brain disorders.

Brain Injury

Abnormal behaviour may occur if the structure of the brain in changed. Phineas Gage had a large part of his brain damaged in an accident, whilst he survived he was considerably changed mentally, this could be seen as an abnormality.


+ Doesn’t blame patient – The Biological Model, in its early life, led to a more humane treatment of the patients. Whereas previously abnormality was thought to be caused by demons and evil, there was now a medical reason. This means that the patients were no longer treated as evil or demonic.

+ Brain scans as proof – The use of brain scanning, such as PET, has allowed us to see a biological difference between mentally ill people and mentally healthy people

+ Improvements in treatment – The Biological Model provides us with information from which we can develop treatments. So as a result of the model drug treatments have become much more effective.

+ Research into genetics – Research has shown that many people with abnormalities do have a difference in genetic material.


– Cause and effect isn’t always clear – Research often contradicts the key ideas of the Biological Model. For example, the model states that Schizophrenia is often caused by an excess of Dopamine, however some research shows patients with Schizophrenia can have lower levels of Dopamine than normal

– Treatments cause ethical concerns – The biological model means more widespread use of drugs as a form of treatment, however there are ethical concerns surroundings drugs. For example, patients could become addicted to the drug.

– Reductionist – This model focus’ only on biological problems as a cause of abnormality. However, psychologists argue you need to consider both biological and environmental to explain abnormality

– No conclusive evidence – There is no evidence which states that abnormality is definitely caused by biological differences. For example Gottesman’s research had a 48% concordance rate, although that is quite high, it would have to be 100% to say that biological differences are the cause of abnormality. For this reason it can’t just be the biological model which explains abnormality.


About Sam Cook

A blog set up to help A Level students revise Sociology


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