The Brain

Schizophrenia Revealed To Be 8 Genetically Distinct Disorders

September 15, 2014 | by Lisa Winter

Photo credit: “Neurons” by Birth Into Being via flickr, CC BY-NC-SA 2.0

Just over 1 percent of the American population has been diagnosed with schizophrenia, a severe mental disorder that causes debilitating symptoms including paranoid delusions, auditory hallucinations, and impaired social behavior. A new study has revealed that schizophrenia is not one disease, but eight disorders with genetically distinct causes. This could dramatically change how schizophrenia is diagnosed and treated. The research was led by C. Robert Cloninger of Washington University School of Medicine in St. Louis and the results were published in The American Journal of Psychiatry.

To identify the genetic roots of schizophrenia, Cloninger’s team analyzed the genomes of 4,200 individuals diagnosed with schizophrenia and 3,800 controls. They looked at almost 700,000 single nucleotide polymorphisms (SNPs) within the genome, which are common locations for genetic variation by only one base pair. 

They were then able to sort the schizophrenic patients by symptom type and severity and compare SNPs. They found that it wasn’t one or even a small handful of genes acting independently to cause one disorder, but it was a total of 42 genetic clusters working together that were responsible for bringing out the symptoms for not one disease, but 8 separate disorders

“Genes don’t operate by themselves. They function in concert much like an orchestra, and to understand how they’re working, you have to know not just who the members of the orchestra are but how they interact," Cloninger said in a press release. “What we’ve done here, after a decade of frustration in the field of psychiatric genetics, is identify the way genes interact with each other, how the ‘orchestra’ is either harmonious and leads to health, or disorganized in ways that lead to distinct classes of schizophrenia.”

Previous studies have found weak affiliations between individual genes and schizophrenia, though it was hard to reproduce the results. Given this new development, it makes sense. Not everyone with schizophrenia exhibits all possible symptoms, and therefore wouldn’t have the same genetic markers causing the illness. The results of this study provide incredibly clear connections between SNPs and symptoms. Certain genetic variations were 95% accurate in predicting delusions and hallucinations, while other SNPS were 100% accurate in estimating speech and behavior anomalies associated with schizophrenia.

Though there are environmental factors such as drug use and emotional trauma that contribute to the onset of schizophrenia symptoms, the disorder is attributed to genetics about 80% of the time. This could be profoundly helpful in correctly diagnosing and treating a large number of patients who are severely suffering because of their symptoms.

“People have been looking at genes to get a better handle on heart disease, hypertension and diabetes, and it’s been a real disappointment,” Clonginger concluded. “Most of the variability in the severity of disease has not been explained, but we were able to find that different sets of genetic variations were leading to distinct clinical syndromes. So I think this really could change the way people approach understanding the causes of complex diseases.”

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