(February 7, 2017) Individualized risk aessment is already used to promote prevention and achieve better outcomes for health conditions including heart disease and breast and prostate cancer. Calculators for these diseases equip medical providers to make risk predictions for individual patients based on how the individual’s disease indicators compare with a large sample of similar cases.
Psychotic conditions such as schizophrenia have not yet benefited from such tools, even though most individuals who develop these diseases have subtle early symptoms that could be assessed.
Now, a team of researchers from the United States and Canada has developed a risk calculator that eventually could change that. Tyrone D. Cannon and colleagues followed 596 participants in the North American Prodrome Longitudinal Study to develop a calculator that predicts the likelihood an individual with prodromal symptoms of schizophrenia will convert to psychosis within two years of assessment.
Reporting in the American Journal of Psychiatry, the authors say their “practical tool” makes “a well-performing risk calculator for psychosis” available for use by trained clinicians with new patients who meet criteria for a psychosis risk syndrome.
Risk Factors for Psychosis
Use of the calculator begins with screening on the Structured Interview for Psychosis Risk Syndromes (SIPS) and identification as “high risk.” High-risk cases involve individuals who are experiencing subtle changes in belief, thought and perception that appear to be precursors of delusions, thought disorder and hallucinations, respectively.
Among individuals aged 12-35 years old who experience such prodromal symptoms, approximately 20%-25% go on to develop psychosis within two years, a risk 100 times greater than for the general population of the same ages. However, say the authors, “this estimate ignores the fact that clinical high-risk cases vary considerably in risk.” The purpose of the calculator is to identify those at the high end of this spectrum.
The authors found a number of factors associated with higher risk of conversion to psychosis including
- higher levels of unusual thought and suspiciousness
- greater decline in social functioning
- lower verbal learning and memory performance
- slower speed of processing
- younger age at baseline
More severe prodromal symptoms were associated with higher risk for conversion. Stressful life events, trauma and family history were not significant predictors of future psychosis.
“Given limitations of available treatments for schizophrenia, with most patients showing substantial deficits in social and occupational functioning through life, there is considerable interest in developing preventative approaches to psychotic disorders,” the authors said.
Practical Implications
If developed into a tool used in clinical practice, the authors say it “may be useful for weighing the cost-benefit ratios of various treatment options.”
“Treatments associated with greater risks to the patient (e.g., medication side effects) or greater costs to health care delivery systems (e.g., resource- and time-intensive psychotherapeutic interventions) may be best reserved for those with higher-than-median levels of predicted risk (i.e., ≥0.16), while cost-effective treatments with benign side effect profiles may be the best option for those whose predicted risk for psychosis is in the lower range.”
For now, the calculator requires patients to be screened first and identified as high risk by trained evaluators, which limits the immediate usefulness of the tool to researchers and research-driven treatment trials, according to the authors. Safeguards have been built into the online device to prevent untrained individuals from using it and arriving at unsupportable conclusions.
A “Mirror Game” Approach
The quest for earlier psychiatric disease detection and the preventative potential that comes with it were behind another novel approach to diagnosing schizophrenia earlier, this one reported February 1 in npj Schizophrenia.
In “Unravelling socio-motor biomarkers in schizophrenia,” Piotr Słowiński and colleagues describe a “mirror game” in which a patient’s hand movements are observed both alone and while trying to mimic the movements of a computer avatar or robot. Individuals with schizophrenia have different neuromotor biomarkers than the general population (e.g., longer reaction times, poor motor coordination and weaker interpersonal coordination). Researchers were able to identify the patients with schizophrenia with 93% accuracy during trials of the technique.
With barely 1% of the population affected, “schizophrenia ranks among the most substantial causes of death worldwide and is considered as one of the top 25 leading causes of disability,” according to the authors. They described the mirror-game approach as a “low-cost and non-invasive” tool in cases of “diagnostic uncertainty.”
Doris A. Fuller
Chief of Research and Public Affairs
References:
- Cannon, TD et al. (October 2016). An individualized risk calculator for research in prodromal psychosis. American Journal of Psychiatry.
- Słowiński P et al. (1 February 2017). Unravelling socio-motor biomarkers in schizophrenia. nature partner journals Schizophrenia.
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