The term ‘schizophrenia' covers a group of serious psychotic disorders characterised by a loss of contact with reality. It comes from two Greek words: schiz meaning ‘split' and phren meaning ‘mind'. DSM IV (1994) estimate that the occurrence rate of schizophrenia ranges from 0.2%-2.0% worldwide. There are two main explanations of schizophrenia: the biological explanations and the psychological explanations. In this essay I will critically consider the biological explanations. These include genetics, neurochemistry, brain structure and evolution. Genetic factors of schizophrenia can be explained using studies on twins and studies on family history. With twin studies researchers want to establish the degree of concordance. This is …show more content…

Phenothiazines are neuroleptics drugs that block dopamine at the synapse. These typically reduce many of the symptoms of schizophrenia (Davison and Neale, 1996). However they have more effect on positive symptoms such as hallucinations and delusions than on negative symptoms such as apathy and withdrawal.
More support for dopamine's role in schizophrenia comes from the drug L-dopa, which increases dopamine levels. When given this, schizophrenic symptoms may occur (Davison et al., 1987). Van Kammen, Docherty and Bunney, 1982 have also found that symptoms of schizophrenic patients may become worse when given amphetamines, which activates dopamine. Also the symptoms of amphetamine psychosis are similar to paranoid schizophrenia (Prentice, 2000).
Patients suffering from Parkinson's disease provide more support for the dopamine theory. Parkinson's disease is associated with low levels of dopamine and patients suffer uncontrollable limb shaking. Similar uncontrolled movement is found in schizophrenic patients given neuroleptics drugs, most likely due to the reduced dopamine levels.
However there are some problems with the dopamine hypothesis. Barlow and Durand (1995) pointed out that high dopamine levels maintain schizophrenic symptoms and neuroleptics block dopamine rapidly but the symptoms of schizophrenia are not alleviated for days or weeks after. It is also puzzling that the