Risk calculator for psychosis gives clinicians a valuable new tool

"Our consortium is the first to develop a health risk calculator for psychosis based on a large sample," says Emory psychologist Elaine Walker.

By Carol Clark

A national consortium of researchers has developed an individual risk calculator for schizophrenia and other psychosis, comparable to those for cardiovascular disease and other illnesses.

The free, online tool – for use by qualified clinicians and researchers – is based on a study of hundreds of clinical high-risk participants in the North American Prodrome Longitudinal Study (NAPLS). The American Journal of Psychiatry published the findings by NAPLS, a National Institutes of Mental Health consortium comprised of nine research sites, including Emory University.

“Risk calculators for estimating risk of heart attack, stroke and other illnesses are already used by medical researchers and practitioners,” says Emory psychologist Elaine Walker. “Our consortium is the first to develop a health risk calculator for psychosis based on a large sample. It’s another step in the direction of taking mental disorders into the same realm as other kinds of illnesses, to help reduce the stigma and enhance our ability to treat people.”

Walker, the principle investigator for the Emory University site of NAPLS, specializes in the role of stress and stress neurobiology in the development of psychosis.

“The risk calculator runs on data derived in a clinical setting,” Walker says. “Gathering that information requires that an individual undergo diagnostic testing and an interview by a qualified professional, so the calculator is not something that a lay person could use.”

Epidemiological studies have shown that about 20 to 35 percent of teenagers and young adults who meet criteria for a high-risk syndrome convert to psychosis within two years. The NAPLS researchers wanted to create a practical tool for personalized risk prediction for individual patients.

They generated the risk calculator from the NAPLS phase two cohort data, which included 596 subjects who were diagnosed with Attenuated Psychosis Syndrome. That means they had experienced some recent changes in perception and/or developed unusual thoughts but did not meet the definition of psychosis.

The researchers followed up with the subjects two years later and found that 16 percent had developed psychosis. The ones at the greatest risk were those individuals who were younger when their initial symptoms began, had higher levels of unusual thoughts and suspiciousness, greater declines in social functioning, lower verbal learning skills and slower speeds of mental processing.

The risk calculator determines an individual’s level of risk based on these five factors, together with a family history of schizophrenia and whether they have experienced stressful or traumatic life events.

Clinicians can determine numerical ratings of these variables through diagnosis based on the Structured Interview for Psychosis Risk Syndromes (SIPS). They can then plug these values into the risk calculator tool to determine an individual patient’s risk.

“The risk calculator is extremely user friendly for mental health researchers and clinicians,” Walker says. “It’s a big step forward in the development of more systematic approaches for estimating risk for psychosis and will help medical practitioners and researchers focus their attention on individuals at greatest risk and monitor them more closely.”

Ultimately, the risk calculator may be used to weigh the cost-benefit ratios of treating patients with medication that has side effects or having them undergo time-consuming psychotherapeutic interventions.

Phase three of NAPLS is looking at the possibility of adding a biological component to the risk calculator, such as blood analyses and brain scans.

NAPLS is the largest, most comprehensive study ever funded by the NIMH of adolescents and young adults at risk for developing a psychotic disorder. The goal of the $25 million project is to identify more precise predictors for psychosis, along with a better understanding of the neural mechanisms involved. In addition to Emory, the NAPLS consortium includes: Harvard, Yale, UCLA, UC San Diego, Einstein Medical College and the University of Calgary.

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