TUESDAY, Nov. 17, 2015 (HealthDay News) -- Researchers believe they've identified brain structure differences that increase the risk of hallucinations in people with schizophrenia.
"Hallucinations are very complex phenomena that are a hallmark of mental illness and, in different forms, are also quite common across the general population," said study first author Jane Garrison, from the University of Cambridge in England. "There is likely to be more than one explanation for why they arise, but this finding seems to help explain why some people experience things that are not actually real," she said in a university news release.
The researchers analyzed brain scans of schizophrenia patients and people without the mental illness. They found that schizophrenia patients with hallucinations had structural differences in a certain part of the brain compared to patients who did not hallucinate and people without the disease.
Specifically, schizophrenia patients with hallucinations had a shorter paracingulate sulcus (PCS), a fold near the front of the brain. A 1-centimeter (0.4-inch) reduction in the fold's length was associated with a nearly 20 percent increased risk of hallucinations. The effect held for both auditory and visual hallucinations.
The paracingulate sulcus is one of the last structural folds to develop in the brain before birth, and varies in size between people, according to background information with the study, published Nov. 17 in the journal Nature Communications.
Study leader Jon Simons, a neuroscientist from Cambridge's psychology department, said, "Schizophrenia is a complex spectrum of conditions that is associated with many differences throughout the brain, so it can be difficult to make specific links between brain areas and the symptoms that are often observed.
"By comparing brain structure in a large number of people diagnosed with schizophrenia with and without the experience of hallucinations, we have been able to identify a particular brain region that seems to be associated with a key symptom of the disorder," he explained in the news release.
Garrison, also a member of the psychology department, said the investigators think "PCS is involved in brain networks that help us recognize information that has been generated ourselves." People with a shorter paracingulate sulcus "seem less able to distinguish the origin of such information, and appear more likely to experience it as having been generated externally," she said.
The U.S. National Institute of Mental Health has more about schizophrenia.