Schizophrenia is a psychiatric disorder in which previously normal cognitive abilities and behaviors becomes disturbed. The most common age of onset is just after reaching adulthood, typically the late-teens to the mid-thirties. It is manifested either by so-called positive symptoms (delusions, hallucinations, unusual or disorganized behavior) or by negative symptoms, including a marked lack of activity, loss of interest and unresponsiveness.
Although the precise cause of schizophrenia remains unknown, an enormous amount of research has come up with a number of possibilities. Many early theories focused on behavioral or stress-induced events, but more recently, consensus holds that underlying biochemical abnormalities are more likely the cause. Lending great support to this idea is the fact that genetic predisposition may account for 50 percent of the risk of developing schizophrenia. Not surprisingly, these biochemical hypotheses center on dysfunction of the neurotransmitter systems in the brain, which provide for normal cognition and attention. The main theories include the Dopamine Hypothesis, the NMDA Receptor Hypothesis, the Single-carbon Hypothesis and the Membrane Hypothesis. And new research from our laboratory suggests that elements from each of these theories may play a role in schizophrenia.