Causes and risk factors of Schizophrenia

From research, it has been clear that there is no single known cause for schizophrenia or schizoaffective disorder. Many other diseases like heart disease are caused by the interaction between genetic, behavioral, etc., and schizophrenia also comes under this category.

Causes of Schizophrenia

It has been known for a long that schizoaffective disorder is a genetically inherited disease and runs in families. Persons with close relatives affected with schizophrenia are generally more likely to get schizophrenia than people with no relatives with schizophrenia at all.

A good example is that a person is 40-50% more likely to develop the schizoaffective disorder when an identical twin is affected by schizophrenia. And another illustration is that a child is 10% more likely to get schizoaffective disorder when his parent is affected with schizophrenia. And the risk is just 1% in the normal population to develop schizophrenia.

Research is being conducted to identify the genetic factors which are responsible for schizophrenia. It has been found that several genes are responsible for the development of the disorder. Besides, factors like prenatal difficulties involving viral infections or intrauterine starvation, perinatal complications, etc.

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Some nonspecific stressors act as triggers. But yet the genetic transmission of the disease has not been identified accurately, and hence it is impossible to say if a person will develop a schizoaffective disorder or not.

Various combinations of the human genome are being investigated to identify those involved in schizophrenia. Recent research has proved that chromosomes 13 and 6 may be responsible but not yet certain. When the actual genes are identified exactly, it can help the doctors to treat schizophrenic patients better.

Schizophrenia Genetics Initiative has been established by NIMH (National Institute of Mental Health), which is currently gathering data from a large number of affected people to identify the genes and develop a new treatment model.

The research was conducted to determine whether schizoaffective disorder is caused by a chemical defect occurring in the brain. The basic knowledge linking brain chemistry with Schizophrenia is investigated in depth.

Neurotransmitters are also doubted to be concerned in causing schizoaffective disorder, or it may also be caused by some imbalance in the release of neurotransmitters, especially dopamine and glutamate. It seems to give a promising solution.

The next area of research includes structural abnormality of the brain. Several neuro-imaging techniques, like MRI, PEST, etc., are being tried to identify the brain’s structural differences. Schizophrenic people are found to have enlarged ventricles, and certain regions decreased in size.

Sometimes the defect is with the function like decreased metabolic activity. But these reasons are subtle and are not the only cause for Schizophrenia or found only in Schizophrenic people.

Schizophrenic people’s brain shows small changes in the number and distribution of neurons compared to normal people. But normally, these changes seem to be present even before the illness occurs.

Developmental neurobiologists have found that Schizophrenia can occur as a developmental disorder occurring when brain cells form inappropriate links in the course of fetal development. Such errors though dormant in the beginning stages may show up after puberty since some changes occur in the brain after maturation.

Hence this has led to the identification of prenatal factors.

In other researches, some brain imaging techniques have shown biochemical changes that lead to the start of the symptoms of schizoaffective disorder. Hence this has led to the investigation regarding the neural circuits involved in producing the symptoms.

Risk Factors of Schizophrenia

Through research studies and epidemiology regarding the frequency of occurrence of schizophrenia, scientists have discovered a lot of risk factors involved in the development of a schizoaffective disorder. This research has provided indications and guidance for identifying the causes better.

Considering a group of people, a maximum of 1% of the people (nearly 0.8% only as measured by the National Comorbidity Study) are diagnosed with schizophrenia, which amounts to nearly 2.2 million Americans.

However, everyone does not have the same risk of developing schizoaffective disorder. The risk factors are mostly genetically derived, and hence schizophrenia is a disease involved with the family members. The most significant of the risk factors in the family are:

  • A sibling (brother or sister) with the disease – increases the risk to 9%. This occurs even if the sibling is a non-identical twin.
  • One parent with the disease increases the risk of developing schizophrenia to 13%. It occurs even in the case of an adopted child since this is a chronic mental illness.
  • An identical twin increases the risk to 28%.
  • Both the parents affected with the disease increases the risk of developing schizophrenia to 36%.

Scientists have discovered several risk factors and risk-minimizing factors concerning schizoaffective disorder in diverse groups of people. The other non-familial risk factors include:

  • Living in a thickly-populated city – a person grown in a dense urban area is twice more likely to get schizophrenia than other people in a country.
  • If he is an African American, a person is 1.5 times as much more likely to get schizophrenia than white Americans. But the reason behind this has been that most African Americans live in cities and hence is untrue if people in the country alone are accounted for.
  • A person, if he is of Hispanic origin, is less likely to get schizophrenia. It has been found in a study that Hispanic residents living in Los Angeles were only half likely to get schizophrenia as compared to non-Hispanic residents. But the problem here is that Hispanic people ethnically belong to several racial groups. Hence, it is not clear whether this risk-minimizing factor is due to culture or genetically related.
  • Prenatal exposure to hunger – the children of pregnant women in famine, when subject to hunger during the first three months, are twice more likely to get the schizoaffective disorder.
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Other Risk Factors

All the above factors do not contribute to schizoaffective disorders, but they might serve as a trigger at times. Research is being conducted to identify all these people’s underlying differences to explain their risk level variations.

Stress, though not found to be a factor, is commonly believed to cause schizophrenia. People from traumatic childhoods or abusive families are alone, not likely to get schizoaffective disorders than people from healthy childhoods, considering all other risk factors into account.

But most schizophrenic people have had traumatic childhoods or abusive families or have a compounded tragedy in their life, especially because these children have no other resources or support to cope with their illness.

Some people have come from healthy and supportive families. And it is totally unfair to find fault with the loving parents. Hence the reason behind the cause of schizophrenia is not understood very clearly.


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