Causes and risk factors of Schizophrenia

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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 many factors like genetic, behavioral, etc and schizophrenia also comes under this category.

Causes of Schizophrenia

It has known since 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 he has an identical twin affected with 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 for identifying 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.

There are some nonspecific stressors that 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 better treat schizophrenic patients.

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 upon to identify the structural differences in the brain. The 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 when examined after death shows small changes in the number and distribution of neurons as 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 there are some changes occurring 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 National Comorbidity Study) are diagnosed to have schizophrenia, which amounts to nearly 2.2 million Americans.

However, everyone does not have the same risk of developing the 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 as well as risk-minimizing factors in relation to the occurrence of the schizoaffective disorder in diverse groups of people. The other non-familial risk factors include:

  • Living in a thickly-populated city – a person when grown in the dense urban area is twice more likely to get schizophrenia compared to other people in a country.
  • A person, if he is an African American, is 1.5 times as much more likely to get schizophrenia as compared to white Americans. But the reason behind has been found to be that most of the 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 and 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 especially, are twice more likely to get the schizoaffective disorder.

Other Risk Factors

All the above factors do not contribute to schizoaffective disorders such but they might serve as a trigger at times. Research is being conducted to identify the underlying differences in all these people 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 compared to 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.

There are also people who 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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