Currently, most people think that schizophrenia may be caused by a combination of factors.

   Extensive scientific research supports the viewpoint that a genetic predisposition is a primary factor in causing schizophrenia. Studies have shown that schizophrenia runs in families. About 70 percents of the schizophrenia patients had family members who also suffered from the disease. That is, relatives of schizophrenia sufferers are more likely to develop the condition than people from families that are free from schizophrenia.

   Identical twins share all of the same genes, whereas fraternal (nonidentical) twins share only about half of the same genes. Studies have found that both individuals in the identical twin pairs developed schizophrenia 50 to 60 percent of the time. That rate is about 15 percent for fraternal twins, who do not have identical genes. In the general population, researchers find the rate to be about 1 percent.

Brain Structure and Activity

   In the early research on the brain structure of a schizophrenic, researchers had to rely on autopsies. It has shown that the brains of people with schizophrenia are different than normal brains. Researchers found that schizophrenics had enlarged brain ventricles. These are the canals within the brain where the cerebrospinal fluid circulates.

   Now scientists have developed several techniques for taking pictures of the brain. One of these techniques, called MRI, uses magnetic fields and radio waves to produce pictures of the brain. Another technique is called PET. It uses radiation to measure how much activity is occurring in certain parts of the brain.

    Studies using MRI and PET found that there are differences between the brains of people who have schizophrenia and those who do not. The brain structure of a schizophrenic is smaller and the spaces of the structure are larger. In addition, certain parts of their brain are less active than in healthy people.

    However, these brain abnormalities are not found in all individuals with schizophrenia. They can also be found in patients who are suffering from Alzheimer’s disease and bipolar disorder.

    Some schizophrenia researchers believe that some of the symptoms of schizophrenia maybe caused by having too much neurotransmitter called dopamine in the brain. When given drugs that increase the amount of dopamine, people with schizophrenia experience a worsening of their symptoms. PET scans show that schizophrenic patients’ dopamine receptors absorb more dopamine than those of normal people. And when the schizophrenic patients were given chlorpromazine, it eliminated some symptoms by blocking dopamine receptors in the brain.

Prenatal Damage

   Doctors believe that many of the brain abnormal brain activities and structures in schizophrenics develop before or during birth. Studies show that birth complications like a breech birth, use of forceps during delivery, prolonged labor, and lack of oxygen for the fetus are associated with a high incidence of schizophrenia later in life.

   Prior to birth, exposure to certain viruses or poor nutrition may also cause these types of brain abnormalities. This brain damage does not usually produce schizophrenia before adolescence because special conditions are needed to activate the disease. Researchers think that the triggering conditions during puberty may include hormones that become active at this time, myelination (the completion of the shield called the myelin sheath around nerve cells), and the loss of some nerve cell connections that begins during teen years.

   Several viruses may be a role in schizophrenia, though none are yet proven to be responsible. Some of the viruses suspected of being associated with schizophrenia are cold and flu viruses. Evidence implicating these pathogens comes form studies demonstrating that when such viruses strike a mother during the third to seventh month pregnancy, the virus can infect the fetus and attack certain areas of the brain that are involved in schizophrenia.