Dopamine and Schizophrenia

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No one knows exactly what causes schizophrenia, although it is becoming clearer that there is probably not just one explanation--rather, most experts believe that there are several factors involved in the development of the disease. A number of scientists think that one of these factors may have to do with the amount of dopamine present in the brain.

The Dopamine Hypothesis

The dopamine hypothesis of schizophrenia states that symptoms of schizophrenia are caused by an overactive dopamine system within the brain. Positive schizophrenia symptoms, in particular, are thought to be cause by an overabundance of dopamine.

Scientific Support for the Dopamine Hypothesis

There is a lot of evidence that supports the dopamine hypothesis of schizophrenia. Some of the best support comes from studies of people who abuse amphetamines, as high doses of amphetamines increase levels of dopamine in the brain and cause symptoms similar to schizophrenia. Drugs that block this “amphetamine psychosis” also reduce symptoms of schizophrenia, while amphetamines themselves make symptoms worse.

Other evidence in favor of the dopamine hypothesis includes the fact that some of the most effective drugs for treating schizophrenia are those that block dopamine receptors in the brain. In addition, research has found that children at risk for schizophrenia have abnormal brain wave patterns that are similar to those of adult schizophrenics, and taking drugs that block dopamine receptors reduce these abnormal patterns in children.

Evidence Against the Dopamine Hypothesis

The evidence in support of the dopamine hypothesis isn’t conclusive, and there is additional evidence that raises some questions about the role dopamine plays in schizophrenia. One important thing to note is that amphetamines and some effective schizophrenia drugs alter levels of other neurotransmitters in addition to affecting dopamine, meaning that their effect on schizophrenia symptoms may not be strictly linked to dopamine levels. Another question is raised by the fact that dopamine-blocking drugs work to reduce dopamine levels immediately, but it can take days for symptoms of schizophrenia to improve. If dopamine levels are directly responsible for schizophrenia symptoms, one would assume that symptom improvement would begin immediately.

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