About one percent of the adult population in the U.S. suffers from schizophrenia, according to the National Institute of Mental Health, but the mental disorder is extremely chronic, severe, and disabling. Many answers about the science behind the schizophrenic brain have been revealed through recent studies, but we still don't have a lock on what actually causes the chronic disorder. A new study however points to a potential risk factor.

The research, out of Israel, suggests people who have a brother or sister with schizophrenia are 10 times more likely to develop the mental illness. Lead researcher Dr. Mark Weiser, from the department of psychiatry at Sheba Medical Center in Tel Aviv, called the results "quite striking," Medical Express reported.

"This is a large study which allows us to put meaningful figures on the risks of developing mental disorders after they have arisen in a brother or sister," he said.

Researchers examined siblings of more than 6,000 Israeli patients who were diagnosed and hospitalized with schizophrenia, bipolar disorder or depression. To reach the results, they compared the participants to about 75,000 healthy peers from an Israeli population database.

As Medical Daily previously reported, schizophrenia is characterized by a breakdown of thought processes and by poor emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking. It is also accompanied by significant social or workplace dysfunction.

The study results do not prove cause and effect. Researchers only discovered an association between mental health disorders and risk to siblings.

"These results are important clinically, as they encourage mental health workers to be aware of the increased risk of psychiatric disorders in siblings of patients," Weiser said in a news release. "These results can also be used by researchers studying the genetic underpinnings of mental disorders."

Additionally, it was discovered that people who have a brother or sister with bipolar disorder also have a 20 times higher risk of developing it.

Read more:

Why Does Schizophrenia Start In Adolescence? An Inside Look At The Teen Brain

Schizophrenia Cause Theories 2016: The Brain Chemistry Behind Memory Problems, Cognitive Dysfunction