Research by Mikaywa et al has found that there must be a genetic explanation of schizophrenia due to the fact that concordance rates for environmental causes are not 100%. Also Mikaywa noticed that schizophrenia runs in the family, meaning there must be something other than environmental causes, causing the disorder. What Mikaywa studied was DNA from human families who were affected by schizophrenia and found that those with the disorder are more likely to have the defective gene: PPP3CC. The PPP3CC gene regulates the immune system, and therefore is an important gene in terms of genetic vulnerabilities which may be to the environment. The other biological explanation is The Dopamine Hypothesis. Recent research has suggested that genetic factors affect the hard wiring of the brain. The research focused on the brain biochemistry (neurotransmitters). Although there have been many neurotransmitters associated with schizophrenia, dopamine seems to be the most important. In schizophrenics, dopamine activity is infrequent. This leads to the characteristic symptom of schizophrenia, such as anhedonia, flat affect and asociality. However research has also found that schizophrenics have abnormally high D2 receptors. Overall, the dopamine hypothesis suggests that schizophrenia is a result of high activity or high D2 receptors.
Research into dopamine hypothesis comes from medication given to schizophrenics and healthy individuals. Amphetamines are drugs which produce a state closely linked to paranoid schizophrenia. They can also exacerbate the symptoms of those who currently have schizophrenia. They release three neurotransmitters, the bulk of which is dopamine. Researchers are sure of the fact that the psychosis induced effect of amphetamines is due to increase in dopamine as antipsychotics are an effective treatment for amphetamine psychosis.