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(Jan. 28, 2016) — Scientists may have found another clue to the cause of schizophrenia. A new study some scientists are labeling “groundbreaking” comes from researchers at Harvard, the Broad Institute and Boston Children’s Hospital and is published in the latest edition of Nature.

Schizophrenia can be a devastating psychiatric disorder that warps a person’s understanding of reality and sense of self. There is no cure and while treatment has improved significantly, allowing some people to live productive lives, there is still no way to prevent or eliminate the root problem of the mental disorder that affects more than 21 million people worldwide. The World Health Organization estimates one in two people living with schizophrenia do not get any treatment.

Up until now, scientists have understood some of the mechanics of the disorder and have noted that a person with schizophrenia loses gray matter and has a smaller number of synaptic structures in their brain. But what they haven’t understood is what might cause that.

This new study’s hypothesis is that people with schizophrenia have a variation of a gene called C4 that creates two varieties of proteins: C4-A and C4-B. Looking at the genes of 64,000 people, those who struggled with schizophrenia had C4 genes that produced overactive forms of the C4-A protein.

What does that mean exactly? What the authors suggest is that people with schizophrenia who carry these genes have a problem with a natural process in the brain called synaptic pruning. The gene is also involved with regulating the immune function. The brain has cells that act a bit like a cleaner that helps the brain get rid of clutter. As you develop and learn things, these cells remove the redundant or weak connections between your synapses. Synapses are like intersections on roads that carry information through your brain. After a good street cleaning, what’s left behind are clearer intersections and stronger, healthier connections.

When you are a teen or a young adult, these cleaner cells are working overtime in the part of your brain called the prefrontal cortex. That’s the front part of your brain that is involved in helping you make plans and choices. In a schizophrenic’s brain, the theory is, this cleaner is overly aggressive. Often the symptoms of schizophrenia appear in the late teen or early adult years. When the researchers tested this theory by breeding mice without the gene that produces this protein, the synaptic pruning mechanism in their brains malfunctioned.

The new research gives scientists an important piece of the biological puzzle, but it doesn’t mean there will be a cure anytime soon, nor would scientists be able to screen for the gene and determine who would definitely develop schizophrenia. The disorder is much more complicated.

“Having a gene implicated in a mental illness does not determine your fate,” said Dr. Daniel Weinberger. Weinberger is the director and CEO of the Lieber Institute for Brain Development and a leading researcher on the genetic mechanisms that cause abnormal brain development and its risk for schizophrenia. “This is beautiful research that helps us better understand at a basic biological level what this tiny risk means for a developing brain.”

But it’s not so clear how big a roll this plays in the development of the disease.

It’s an important but incremental step, because if you inherit this gene, he said, your likelihood of developing schizophrenia goes up a tiny bit. One out of 200 people have schizophrenia, according to the CDC, but if you have this gene the odds that you will develop schizophrenia go up to about 1 out of 180. Having the gene may increase the likelihood of your developing the disorder, but other factors are likely needed. “The question is then, what tips the scale enough?” Weinberger said.

Discovering factors, even small ones, is significant. “This is a landmark study because it provides the most definitive evidence that we have implicated specific genes that cause schizophrenia,” said Dr. Jeffrey Lieberman. Lieberman is the chairman of Psychiatry at Columbia University College of Physicians and Surgeons whose research has also led to significant advances in the early detection and care for people with schizophrenia. “In doing so (the study) opens the door to a diagnostic approach and also a new pathway for treatment development that we hadn’t been developing.”