After a century of schizophrenia genetic research, neuroscientists are still unable to conclusively determine its cause. What is known is that there is an abnormal balance among neuronal circuits or pathways due to gene mutation. Non-genetic contributions like viral infections during pregnancy or low level inflammation and head injury are also possible causes. Current medications only suppress positive symptoms like delusions, hallucinations, and thought disorder (Negative symptoms, like decreased motivation, diminished emotional expression, and motor abnormalities and cognitive deficits are not treated by antipsychotic drugs). About 50% of patients under treatment have adverse side effects to current available medication, and we do not yet know why this is happening. 90% of schizophrenic patients smoke, as the nicotinic receptors activated in the brain seemed to aid in their cognitive enhancement.
(This Drugs and the Brain Course is by far the most challenging in terms of technical details handled, but is extremely enlightening.)