The Maudsley environmental risk score for psychosis.

Evangelos Vassos,Robin M Murray,Charlotte Gayer-Anderson,Antonella Trotta,Craig Morgan,Simona A Stilo,Marta Di Forti,Cathryn M Lewis,Pak Sham,Matthew Kempton

doi:10.1017/s0033291719002319

Abstract

Risk prediction algorithms have long been used in health research and practice (e.g. prediction of cardiovascular disease and diabetes). However, similar tools have not been developed for mental health. For example, for psychotic disorders, attempts to sum environmental risk are rare, unsystematic and dictated by available data. In light of this, we sought to develop a valid, easy to use measure of the aggregate environmental risk score (ERS) for psychotic disorders. We reviewed the literature to identify well-replicated and validated environmental risk factors for psychosis that combine a significant effect and large-enough prevalence. Pooled estimates of relative risks were taken from the largest available meta-analyses. We devised a method of scoring the level of exposure to each risk factor to estimate ERS. Relative risks were rounded as, due to the heterogeneity of the original studies, risk effects are imprecisely measured. Six risk factors (ethnic minority status, urbanicity, high paternal age, obstetric complications, cannabis use and childhood adversity) were used to generate the ERS. A distribution for different levels of risk based on simulated data showed that most of the population would be at low/moderate risk with a small minority at increased environmental risk for psychosis. This is the first systematic approach to develop an aggregate measure of environmental risk for psychoses in asymptomatic individuals. This can be used as a continuous measure of liability to disease; mostly relevant to areas where the original studies took place. Its predictive ability will improve with the collection of additional, population-specific data.

Highlights

Patient-tailored risk prediction is routinely applied in medicine and prediction models have been developed for a range of conditions like cardiovascular disease and diabetes (Wilson et al, 1998; Assmann et al, 2002; Wilson et al, 2007; Hippisley-Cox et al, 2008)
We identified six environmental risk factors fulfilling our inclusion criteria: minority ethnic group, urbanicity, high paternal age, obstetric complications, cannabis use and childhood adversity (Table 1)
These were not included in the environmental risk score (ERS) either due to insufficient evidence, difficulty to establish exposure in a clinical interview (e.g. IgG antibodies for T. gondii) or potential of overlap with other included risk factors

Summary

Introduction

Patient-tailored risk prediction is routinely applied in medicine and prediction models have been developed for a range of conditions like cardiovascular disease and diabetes (Wilson et al, 1998; Assmann et al, 2002; Wilson et al, 2007; Hippisley-Cox et al, 2008) These models use a combination of risk factors, including anthropometric traits (e.g. BMI, blood pressure), lifestyle (e.g. smoking), biochemistry tests (e.g. glucose or cholesterol levels) and family history of illness. These prediction models are included in clinical guidelines for prevention [e.g. cardiovascular disease: risk assessment and reduction, including lipid modification (CG181) or familial breast cancer (CG164), https://www.nice.org.uk/] and are increasingly advocated in public health (Damen et al, 2016). Its predictive ability will improve with the collection of additional, population-specific data

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Conclusion