How well does the dopamine hypothesis explain the development of schizophrenia?

The dopamine hypothesis states that schizophrenia is caused by increases in the amount of the neurotransmitter dopamine in the brain. This theory is supported by research that showed that the use of amphetamines, which increase the amount of dopamine in the brain, can induce symptoms akin to those seen in schizophrenia, and can exagerrate the positive symptoms of schizophrenia in people with the disorder (Laurelle, 1996). There is also research to suggest that the positive symptoms of schizophrenia can be linked with an increase in the production of dopamine (Howes, 2009). However, increased dopamine appears to be linked only to the positive symptoms of schizophrenia, such as hallucinations and delusions, and does not appear to explain the cognitive or negative symptoms. Most antipsychotics work by reducing the amounts of dopamine in the brain, however, as reported by Noll (2009), around a third of people with schizophrenia do not respond to these types of anipsychotics. There is also currentlylittle evidence as to whether increased dopamine occurs before the development of schizophrenia or whether it happens as an effect of schizophrenia.

While current research suggests that there is a increase in dopamine in many people with schizophrenia, this is not the case for all people with the disorder. Increased dopamine also does not appear to explain all of the symptoms of schizophrenia and we are unable to tell at present whether this is a cause of the disorder or an effect of it.