Schizophrenia clearly involves irregularities in the chemicals of the brain (neurochemicals) that allow brain cells to communicate with each other. We know this because blocking certain neurotransmitters with drugs (like amphetamine or PCP) can cause schizophrenia-like symptoms. Also, antipsychotic medications that block the action of the neurotransmitter dopamine can effectively reduce symptoms.
In fact, dopamine imbalance was once thought to cause schizophrenia. However, more recent antipsychotics work without blocking dopamine. Current research indicates that the neurotransmitters GABA and glutamate are involved in the cause of schizophrenia.
The difficulty of neurochemical theories is that most brain processes can affect neurotransmitter levels, and neurotransmitters (of which there are at least 100) all interact with one another. When we say that one particular neurotransmitter or another is causing schizophrenia, we are basing that claim on a single frame of a very long and complicated motion picture, without being able to see the frames that led up to the change we’re observing.
The medical treatment of schizophrenia today relies almost entirely upon regulating levels of neurotransmitters, and so research in this area is vital to developing more effective treatments.