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Distress in pregnancy ‘turns on’ schizophrenia genes in the placenta, new study reveals 

Genes within the placenta could signal a higher risk of schizophrenia, a new study shows.

During complicated pregnancies, such as high blood pressure, schizophrenia genes in the placenta are ‘turned on’ and they signal that the organ is under duress, according to researchers from the Lieber Institute for Brain Development in Maryland.

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Previous studies have focused on how genes related to behavioral disorders directly alter prenatal brain development.

The placenta provides oxygen and nutrients to a growing baby and removes waste products from the baby’s blood.  

This is the study is the first to show that many genes associated with risk for schizophrenia appear to change early brain development indirectly when the health of the placenta is compromised.

Schizophrenia genes within the placenta are ‘turned on’ when a woman experiences a complicated pregnancy, raising the risk of the disorder, a new study shows

For the study, investigators looked at data on 2,800 adults from four countries – spanning the US, Europe and Asia.

Of the participants, 2,038 had been diagnosed with schizophrenia, a chronic mental disorder that affects how a person thinks, feels, and behaves along with a failure to understand reality. 


Schizophrenia is a chronic and severe mental disorder that affects how a person thinks, feels, and behaves. 

People with schizophrenia may seem like they have lost touch with reality.

The cause of schizophrenia is not understood and it is believed to be a mix of genetics (hereditary), abnormalities in brain chemistry and/or possible viral infections and immune disorders. 

Symptoms of schizophrenia usually begin between ages 16 and 30. In rare cases, children have schizophrenia too.

The symptoms of schizophrenia fall into three categories: positive, negative, and cognitive.   

Positive symptoms are disturbances that are ‘added’ to the person’s personality and include:

  • Hallucinations
  • Delusions
  • Thought disorders (unusual or dysfunctional ways of thinking) 

Negative symptoms are capabilities that are ‘lost’ from the person’s personality and include: 

  • ‘Flat affect’ (reduced expression of emotions via facial expression or voice tone)
  • Reduced feelings of pleasure in everyday life
  • Difficultly beginning and sustaining activities 

Cognitive symptoms are changes in their memory or other aspects of thinking and include:

  • Trouble focusing or paying attention
  • Problems with ‘working memory’
  • Poor ability to understand information and use it to make decisions 

Figures suggest around one percent of the world population suffers from schizophrenia with around two million in the US.

Source: National Institute of Mental Health 

Past studies have shown that up to 80 percent of the risk of developing the disorder is genetic. 

All of the participants had undergone genetic testing and were surveyed for pregnancy history information.

Researchers found a high correlation of genes associated with risk for schizophrenia and a history of a potentially serious pregnancy complications. 

Individuals who have a high genetic risk and whose mothers had complications during pregnancy had at least a five-fold greater risk of developing schizophrenia in comparison to individuals with similarly high genetic risk but no history of serious obstetrical complications.

From there, the team analyzed gene expression – the way that genes are coded to produce DNA – in multiple placenta tissue samples, including samples of placenta from complicated pregnancies that include preeclampsia and intrauterine growth restriction. 

Consistently, in women with complicated pregnancies, schizophrenia genes in the placenta were ‘turned on’ and, the more they were turned on, the more the placenta showed other signs of being under stress, for example, being more inflamed.

‘For the first time, we have found an explanation for the connection between early life complications, genetic risk, and their impact on mental illness and it all converges on the placenta,’ said Dr Daniel Weinberger, lead study investigator and CEO of the Lieber Institute.

With many developmental behavioral disorders, including schizophrenia, ADHD and autism, one mystery has been that incidence rates are two to four times higher in men than in women.

The Lieber Institute team found that the schizophrenia genes turned on in the placenta from complicated pregnancies were dramatically more abundant in placentas from male children compared with female children. 

‘The surprising results of this study make the placenta the centerpiece of a new realm of biological investigation related to how genes and the environment interact to alter the trajectory of human brain development,’ said Dr Weinberger.     

Dr Weinberger says he hopes future research focuses on therapeutic treatments and prevention strategies to ultimately reduce the incidence of these behavior disorders. 


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