Critically Consider Biological Explanations of Schizophrenia
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