A theory postulating that the pathogenesis of schizophrenia and other psychotic states is due to excesses in dopamine activity in various areas of the brain. This theory is based in part on observations that the antipsychotic properties of specific drugs may be related to their ability to block the action of dopamine (and hence treat the symptoms of psychosis) and the opposite effects observed with psychotomimetic drugs such as amphetamines that increase the action of dopamine (which may produce symptoms of psychosis).