There are 4 kinds of medical explanation that can be used to explain the cause of abnormality:

Infection:

Genes or micro organisms such as bacteria or viruses are known to produce disease. Some mental illnesses are caused this way (i.e. general paresis). Micro-organisms have also been suggested as a cause of schizophrenia – Barret et Al (1990) found that there was an increased incidence of schizophrenia in children whose mothers had the flu during pregnancy.

Genetic Factors:

Individuals may inherit predispositions to certain illnesses, which are carried through genes. One way of looking at the inheritance of mental illnesses is by studying identical twins. Kendler, Masterson and Davis (1985) found that relatives of schizophrenics were 18 times more likely to be diagnosed with schizophrenia. Gene – mapping studies have found that specific genes may be associated with particular illnesses. Gottesman (1991): Carried out a meta – analysis of approx. 40 twin studies. It was found that having an identical twin with schizophrenia gave you a 48% chance of developing the condition. This reduced to 17% in non identical twins – it was concluded that schizophrenia has a strong genetic basis.

Biochemistry:

Suggests that a raised amount of biochemical levels may cause mental illness although it is not clear whether this raise in biochemical levels is the cause or the effect of mental illness.

Neuroanatomy:

This means that something in the structure of the immune system is linked to mental illness. For example amnesia occurs because part of the brain (where long term memory is stored) has been damaged.

Implications of the Biological model for treatment:

If mental illnesses are basically illness of the body, the treatment should involve direct manipulation of bodily process. For example, if a mental disorder involves biochemical abnormalities, then drugs may be prescribed to correct this. Other examples of treatment are psychosurgery (removing part of the brain to save the mind) and electro – convulsive therapy (passing a small electric current though the brain resulting in electro convulsion)

Psychosurgery:

It is fully effective in approx. 1/3 of cases, some what effective in another third of cases, and not at all effective in a third of cases. Psychosurgery has major ethical issues because the damage to the brain is irreversible and the outcome is unpredictable. Anybody having psychosurgery must be able to 1st prove to an ethics committee that they are of sound mind.

Electro – convulsive therapy (ECT):

This is occasionally used in the treatment of severe depression. It is unclear why this method works, but one suggestion is that it effects the activity of neurotransmitters in the brain. Where drugs have not worked, ECT has been found to be effective in 50% of cases. This also has ethical concerns as ECT can lead to memory impairment.

Drugs:

Excessive levels of dopamine have been linked to schizophrenia, chlorpromazine and clozapine are anti-psychotic drugs which lower the levels of dopamine. Drugs work in 50-60% of cases of schizophrenia, however they do not cure the disorder and symptoms return in 80% of cases when patients have come off drugs.

There are 2 main groups of drugs for depression: Monoamine-oxidase inhibitors (MAOI’s) and Selective serotonin reuptake inhibitors (SSRI’s). Anti-depressants are effective in 60-70% of cases, however 30% respond to placebos. They target the biological component of depression but do nothing to change the life circumstances that may have caused depression.