A new study has found that perceptual disturbances — a milder form of full-blown hallucinations — are not necessarily predictive symptoms of schizophrenia. Perceptual disturbances may involve seeing shadows or hearing knocking noises with a sense that these experiences are “not real.”

Although some people with perceptual disturbances do go on to develop full-blown psychosis, there are just as many people with these symptoms who do not, according to the researchers.

Instead, they found that suspiciousness and unusual thought content are most likely to signal the onset of the disease. This risk is further enhanced if the person shows difficulty with focus or concentration.

Schizophrenia is a debilitating mental illness that affects more than three million people in the U.S. It typically emerges during late adolescence and early adulthood and remains a chronic and disabling disorder for most patients.

Psychosis, experienced by more than six million Americans, refers to a group of symptoms, including paranoia, delusions (false beliefs), hallucinations, and disorganization of thought and behavior. Psychosis always occurs in schizophrenia, but can also occur in people with bipolar disorder or other medical conditions.

“If we can identify people at high risk for psychosis we can then develop interventions to prevent the development of schizophrenia and the functional declines associated with it,” said Diana Perkins, M.D., a clinician and professor of psychiatry at the University of North Carolina (UNC) School of Medicine and one of the study’s first authors.

“In terms of assessing psychosis risk, I think this study shows we need to be emphasizing the person’s thought process, and appreciate that perceptual disturbances may not be a specific early warning sign. I think that will affect how we develop our diagnostic system in the future for people who are at high risk for psychosis.”

For the study, the researchers analyzed which symptoms were most predictive of psychosis over a two-year follow-up period in a group of 296 individuals at high-risk for psychosis after they had experienced attenuated psychosis symptoms (milder symptoms of psychosis that may be an early warning sign of the full-blown disorder).

Current diagnostic criteria for attenuated psychosis includes at least one of the following: illogical thoughts, disorganized thoughts, or perceptual disturbances of sufficient frequency and severity to impact function.

The analysis revealed that suspiciousness and unusual thought content were the most predictive of full-blown psychosis, and that difficulty with focus or concentration and reduced ideational richness further enhanced psychosis risk prediction.

Suspiciousness and unusual thought content include a feeling of being watched; a feeling that others are talking about you but knowing that this “can’t really be true;” fixating on coincidences that aren’t actually connected; finding “signs” in certain experiences; or having a distorted sense of time. Reduced ideational richness typically refers to difficulty following conversations or engaging in abstract thinking.

Early warning signs of schizophrenia include mild psychosis-like symptoms. However, only about 15-20 percent of people who have these mild psychosis-like symptoms actually develop schizophrenia or other disorders with full-blown psychosis.

“The earlier people are identified and receive treatment when they develop schizophrenia, the better their prognosis,” said Perkins.

The results were published online today in the journal Schizophrenia Research.

Source: University of North Carolina Health Care