Schizophrenia 'made up of eight specific genetic disorders'

Past studies have indicated that rather than being a single disease, schizophrenia is a collection of different disorders. Now, a new study by researchers at Washington University in St. Louis, MO, claims the condition consists of eight distinct genetic disorders, all of which present their own specific symptoms.

The research team, including senior investigator Dr. C. Robert Cloninger, the Wallace Renard Professor of Psychiatry and Genetics at Washington University, says their findings may pave the way for better diagnosis and treatment strategies for schizophrenia.

Schizophrenia is a mental disorder characterized by hallucinations, delusions, abnormal thoughts, cognitive problems and agitated body movements.

People with a family history of schizophrenia are at much higher risk of developing the condition. Approximately 1% of the general population in the US have schizophrenia, but it occurs in around 10% of individuals who have a first-degree relative with the disorder.

Researchers have worked long and hard to identify specific genes associated with schizophrenia. Earlier this year, Medical News Today reported on a study led by researchers from the Cardiff University School of Medicine in the UK, in which they identified 83 new genes linked to schizophrenia.

But Dr. Cloninger says that rather than trying to pinpoint specific genes to schizophrenia development, he and his colleagues wanted to look at how individual genes work together.

Fast facts about schizophrenia in the US

- Schizophrenia is one the leading causes of disability in the US

- Approximately 75% of people who develop schizophrenia are between the ages of 16 and 25

- Past research has indicated that 25% of people with schizophrenia recover completely, 25% have symptoms that do not improve over time, while 50% have symptoms than improve over a 10-year period.

"Genes don't operate by themselves," he says. "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."
Analyzing genetic variations and identifying clusters

For their study, results of which are published in The American Journal of Psychiatry, the team analyzed the genomes of 4,200 people with schizophrenia and 3,800 people without the disorder.

Specifically, they looked at almost 700,000 areas of the genome where a variation occurred in a single unit of DNA. This variation is known as a single nucleotide polymorphism (SNP).

By comparing the SNPs of schizophrenic individuals with those of healthy controls, the team was able to identify the genetic variations linked to schizophrenia. Individuals with schizophrenia were divided into groups based on the type and severity of their symptoms. The team looked at how the genetic variations interacted with each other to produce specific symptoms of the disorder.