incidence has also been compared between monozygotic and dizygotic twins. Over 14 such studies have found higher concordance rates among monozygotic twins (40-50%) than among dizygotic twins. Finally, schizophrenia has additionally been examined among adopted individuals. Although such persons share the genes of their biological family, they are exposed to the environment of their adoptive family. Such studies have revealed that the "prevalence of schizophrenic illness among in the offspring, parents, and siblings of schizophrenic patients who have been reared apart from them remains significantly higher than that in the general population (Kety, 1982, p. 94)."
Such evidence indicates that schizophrenic illness is largely inherited. In addition, it appears that the genetic factors responsible for this mental disorder do not act uniformly, but only occur among specific families. In addition though, environmental influences may also play a role in the development of this disease. Such factors could include the psychosocial interactions associated with rearing, viral infection, diet, and various complications of childbirth (Kety, 1982, p. 95). Taken together, the scientific evidence all seems to emphasize schizophrenia's physiologic basis.
On an anatomic level, researchers have long recognized that the basic functional unit of the nervous system is the nerve cell, or neuron. This cell transmits electrochemical impulses through its specialized parts to other neurons. Of these, the dendrites receive information, and the axons transmit it. The narrow gap which separates the axon of one neuron from the dendrite of another is known as a synapse. Electrochemical impulses are transmitted across this space by way of neurotransmitters (Brown & Mann, 1985, p. 141). Released from the presynaptic nerve terminal, these chemicals diffuse across the synaptic cleft.
In addition to neurotransmitters, another group of chemic...