Schizophrenia Is Actually Eight Distinct Genetic Disorders: New Study

Laszlo Balogh/Reuters

On September 15, the Washington University School of Medicine published a study in The American Journal of Psychiatry revealing that schizophrenia, commonly thought of as a single mental disorder, is actually a group of eight distinct afflictions.

People with schizophrenia are typically diagnosed in their 20s, which is when symptoms (such as delusions and hallucinations) begin to manifest. The brain disorder affects about 1 percent of the population, and it is highly genetic: According to the NIH, having a relative diagnosed with schizophrenia increases one's chances of developing the disorder by 10 percent, while having an identical twin with the disorder raises the risk to 40 to 65 percent.

Previous research on the genetic aspects of schizophrenia has focused on analyzing gene sequences, but scientists have had trouble locating the specific genes in which the disorder originates. For this study, investigators took a much wider approach and examined clusters of genes. The researchers analyzed the DNA of 4,200 patients who had been diagnosed with the disorder in the past, as well as 3,800 individuals with no history of the disease. Researchers grouped patients based on their symptoms—such as difficulty in connecting emotions and thoughts and varying kinds of hallucinations—and the severity of those symptoms.

Then, investigators began matching those symptoms with people's unique genetic features to create genetic profiles. Results indicated that certain genetic profiles made people more susceptible to developing schizophrenia at some point in their lives. For instance, researchers discovered that disorganized behavior and speech patterns were linked to group of DNA variations that brought along with it a 100 percent risk of schizophrenia. Patients with delusions were connected to genetic variations that created a 95 percent chance of schizophrenia. Ultimately, the researchers discovered that eight distinct forms of genetically based schizophrenia currently exist, with symptoms ranging from mild to severe.

Senior investigator Dr. C. Robert Cloninger said in a press release that analyzing how genes interact with each other is crucial for developing improved diagnoses and treatment of schizophrenia. "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 that orchestra are but how they interact."

But despite identifying fairly clear indicators of heightened risk, researchers are still unsure why someone who possesses, say, a 60 percent chance of developing schizophrenia might never become afflicted with the disorder. Speaking to USA Today, Cloninger emphasized that besides genetics, environment is a huge risk factor for schizophrenia. For example, high stress levels and substance abuse—especially marijuana and stimulants—have been linked to schizophrenic behavior, according to the NIH.

But despite a continued lack of clarity around the exact cause of schizophrenia, having the ability to predict high risk within genetic clusters is an enormous step forward. The hope is that doctors will eventually be able to give individuals a more personalized diagnosis and perhaps identify at-risk individuals, and assist them in taking steps toward early prevention.

Ultimately, these types of genetic studies could even lead to more fine-tuned schizophrenia treatment, homing in on treating certain systems based on precise pathways within DNA. In addition, this DNA-based approach to disease classification may be useful to dissect other hereditary disease, including heart disease and diabetes, Cloninger says.