Causes

No single cause can account for schizophrenia. Rather, it appears to be the result of multiple causes such as genetic factors, environmental and psychological assaults, and possible hormonal changes that alter the brain's chemistry.

Abnormalities in Brain Structure, Circuitry, and Chemicals

Brain scans using magnetic resonance imaging (MRI) have shown a number of abnormalities in the brain's structure associated with schizophrenia. Such problems can cause nerve damage and disconnections in the pathways that carry brain chemicals.

Because these problems tend to show up on brain scans of people with chronic schizophrenia rather than newly diagnosed patients, some experts believe they may be a result of the disease and its treatments rather than a cause. (Medications used for schizophrenia can also cause brain shrinkage over time.)

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Abnormal Brain Activity and Volume. Imaging techniques have revealed abnormal brain activity and shrinkage (reduced volume) in the brains of people with schizophrenia. Of particular importance are those in the prefrontal cortex, which contains the white matter of the brain, and the temporal lobes, which contain the limbic system.

The limbic system of the brain is a group of structures that control emotions and behavior. This system (in particular, the hippocampus and amygdala) is involved in the formation of long-term memory, and is closely associated with the olfactory structures, which play a role in the sense of smell.

Click the icon to see an image of gray and white matter of the brain.

Shrinkage of the prefrontal cortex has been seen in many patients with schizophrenia. This can damage nerve cells and impair the connections that are required for verbal memory, attention, decision-making, reasoning, aggression, and meaningful speech. Impairment in the left side of the cortex is also associated with auditory hallucinations (hearing voices). Not all patients have this deficit.
Shrinkage in the limbic areas of the brain is associated with problems finding words. The limbic areas of the brain contain the hypothalamus (controls physiological functions), amygdala (responsible for arousal and emotional states), and hippocampus (the part of the brain that makes memories). A number of studies have specifically noted smaller left hippocampi in people with schizophrenia. Activity in the limbic area in general is related to emotions and memory, and abnormalities there are also associated with positive symptoms, including delusions, hallucinations, and disordered thinking.