Towards a public health approach to psychotic disorders

The 21st century has brought about a burgeoning recognition of the central role of mental health and illness to overall population health. The emphasis of these public mental health efforts has largely been on mental wellbeing and common mental disorders, such as depression, anxiety, and substance use disorders, with less focus on rarer conditions, such as psychotic disorders. Psychotic disorders, which include schizophrenia, bipolar disorder, depression with psychotic features, and substance-induced psychoses, are increasingly recognised as an important public health issue. Despite being a rare condition,1Charlson FJ Ferrari AJ Santomauro DF et al.Global epidemiology and burden of schizophrenia: findings from the Global Burden of Disease Study 2016.Schizophr Bull. 2018; 44: 1195-1203Crossref PubMed Scopus (514) Google Scholar schizophrenia is one of the top 20 leading contributors to years lived with disability globally,2GBD 2017 Disease and Injury Incidence and Prevalence CollaboratorsGlobal, regional, and national incidence, prevalence, and years lived with disability for 354 diseases and injuries for 195 countries and territories, 1990–2017: a systematic analysis for the Global Burden of Disease Study 2017.Lancet. 2018; 392: 1789-1858Summary Full Text Full Text PDF PubMed Scopus (5898) Google Scholar largely due to the young age at onset, high disability weighting, and often chronic course of illness. The public health effects are further compounded by the 15-year reduction in life expectancy faced by people with psychotic disorders,3Hjorthøj C Stürup AE McGrath JJ Nordentoft M Years of potential life lost and life expectancy in schizophrenia: a systematic review and meta-analysis.Lancet Psychiatry. 2017; 4: 295-301Summary Full Text Full Text PDF PubMed Scopus (514) Google Scholar mainly attributable to the high prevalence of comorbid physical health conditions in this population. In this issue of The Lancet Public Health, Hannah Jongsma and colleagues4Jongsma HE Turner C Kirkbride JB Jones PB International incidence of psychotic disorders, 2002–17: a systematic review and meta-analysis.Lancet Public Health. 2019; 4: e229-e244Summary Full Text Full Text PDF PubMed Scopus (105) Google Scholar make an important contribution towards a public health approach to psychotic disorders through an extensive systematic review and meta-analysis of the international literature on the incidence of psychotic disorders. This review was an ambitious initiative, combining estimates from 177 citations spanning 26 countries. Their findings suggest that the incidence of psychotic disorders might be higher than previously believed, at 26·6 per 100 000 person-years, with marked variation across diagnostic categories.5Jongsma HE Gayer-Anderson C Lasalvia A et al.Treated incidence of psychotic disorders in the multinational EU-GEI Study.JAMA Psychiatry. 2018; 75: 36-46Crossref PubMed Scopus (173) Google Scholar The overarching conclusion of this review was that the heterogeneity in incidence estimates was high, largely due to two primary sources. First, the heterogeneity in estimates was due to differences in methodology, with variation by case definition and sources of data employed. Studies that used large population registries or administrative health data tended to find a higher incidence of psychotic disorders than first contact studies that used standardised diagnostic procedures coupled with comprehensive case ascertainment strategies.4Jongsma HE Turner C Kirkbride JB Jones PB International incidence of psychotic disorders, 2002–17: a systematic review and meta-analysis.Lancet Public Health. 2019; 4: e229-e244Summary Full Text Full Text PDF PubMed Scopus (105) Google Scholar Many regions rely on these population-based datasets to inform public health strategies; although powerful, they often have insufficient standardisation across providers, institutions, and health-care systems. Conversely, first contact studies might represent a more rigorous epidemiological approach to obtaining data on the population distribution of psychotic disorders, but the intensity of resources required might render them unfeasible for ongoing population surveillance. Second, the analysis by Jongsma and colleagues highlights the substantial heterogeneity in the incidence of psychotic disorders across different countries and regions.5Jongsma HE Gayer-Anderson C Lasalvia A et al.Treated incidence of psychotic disorders in the multinational EU-GEI Study.JAMA Psychiatry. 2018; 75: 36-46Crossref PubMed Scopus (173) Google Scholar Although the variation in the present Article is confounded by differences in methodology, this heterogeneity is more clearly illustrated by the EU-GEI study,5Jongsma HE Gayer-Anderson C Lasalvia A et al.Treated incidence of psychotic disorders in the multinational EU-GEI Study.JAMA Psychiatry. 2018; 75: 36-46Crossref PubMed Scopus (173) Google Scholar which found an 8-times difference in incidence estimates across five countries and 16 catchment areas using a consistent approach across sites. Studies that use consistent and standardised metrics are crucial for furthering understanding of the causes of psychotic disorders because differences across sites can provide important insights on key risk factors.6Di Forti M Quattrone D Freeman TP et al.The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-GEI): a multicentre case-control study.Lancet Psychiatry. 2019; (published online March 19.)https://doi.org/10.1016/S2215-0366(19)30048-3Summary Full Text Full Text PDF PubMed Scopus (357) Google Scholar Also noteworthy in the findings from Jongsma and colleagues is the almost complete absence of estimates from low-income and middle-income countries,4Jongsma HE Turner C Kirkbride JB Jones PB International incidence of psychotic disorders, 2002–17: a systematic review and meta-analysis.Lancet Public Health. 2019; 4: e229-e244Summary Full Text Full Text PDF PubMed Scopus (105) Google Scholar which has also plagued larger-scale initiatives, such as the Global Burden of Disease study.1Charlson FJ Ferrari AJ Santomauro DF et al.Global epidemiology and burden of schizophrenia: findings from the Global Burden of Disease Study 2016.Schizophr Bull. 2018; 44: 1195-1203Crossref PubMed Scopus (514) Google Scholar, 7Whiteford HA Ferrari AJ Degenhardt L Feigin V Vos T The global burden of mental, neurological and substance use disorders: an analysis from the Global Burden of Disease Study 2010.PLoS One. 2015; 10: 1-14Crossref Scopus (716) Google Scholar Given that the burden of mental disorders is rapidly increasing in these contexts as a result of the epidemiological transition from infectious diseases and malnutrition to more chronic conditions, psychotic disorders in these settings need to be better understood. To advance a public health approach to psychotic disorders, a standardised metric for monitoring psychotic disorders is needed at the population level, as was so clearly highlighted by the heterogeneous data presented by Jongsma and colleagues.4Jongsma HE Turner C Kirkbride JB Jones PB International incidence of psychotic disorders, 2002–17: a systematic review and meta-analysis.Lancet Public Health. 2019; 4: e229-e244Summary Full Text Full Text PDF PubMed Scopus (105) Google Scholar To borrow an example from the obesity field, public health gains were possible once obesity measurement was standardised through body-mass index.8Wolpert M Rethinking public mental health: learning from obesity.Lancet Psychiatry. 2018; 5: 458-460Summary Full Text Full Text PDF PubMed Scopus (3) Google Scholar Despite the limitations of this measure, it provides a consistent and standardised metric for population health surveillance. The development of such metrics might be quite challenging in public mental health due to the complexity of mental disorders and differences in diagnostic practices across contexts; however, the benefits of having consistent and comparable data across regions, countries, and time periods will outweigh the inevitable limitations associated with such a measure. Many important advances have been made in public mental health for psychotic disorders. Tertiary prevention efforts through early psychosis intervention programmes have proven effective at improving recovery and quality of life among people with psychotic illness.9Correll CU Galling B Pawar A et al.Comparison of early intervention services vs treatment as usual for early-phase psychosis: a systematic review, meta-analysis, and meta-regression.JAMA Psychiatry. 2018; 75: 555-565Crossref PubMed Scopus (335) Google Scholar Although controversial,10Ajnakina O David AS Murray RM ‘At risk mental state’ clinics for psychosis—an idea whose time has come—and gone!.Psychol Med. 2018; (published online Dec 26.)DOI:10.1017/S0033291718003859Google Scholar ongoing research is establishing whether secondary prevention for people at clinical high risk for psychotic disorders is effective. And although the causal mechanisms might not be fully understood, several well established risk factors for psychotic disorders could have important implications for primary prevention, such as social marginalisation and adversity,11van Os J Kenis G Rutten BPF The environment and schizophrenia.Nature. 2010; 468: 203-212Crossref PubMed Scopus (1045) Google Scholar high-potency cannabis use,6Di Forti M Quattrone D Freeman TP et al.The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-GEI): a multicentre case-control study.Lancet Psychiatry. 2019; (published online March 19.)https://doi.org/10.1016/S2215-0366(19)30048-3Summary Full Text Full Text PDF PubMed Scopus (357) Google Scholar and migration.12Selten J van der Ven E Termorshuizen F Migration and psychosis: a meta-analysis of incidence studies.Psychol Med. February 2019; (published online Feb 6.)DOI:10.1017/S0033291719000035Crossref PubMed Scopus (79) Google Scholar However, assessment of the public health effects of these prevention efforts will not be possible without standardised and consistent metrics for population surveillance of psychotic disorders. Additionally, given the marked heterogeneity observed across countries and contexts, it is unlikely that a one size fits all public health solution will be effective, further highlighting the need for high quality standardised data as an important step towards a public health approach to psychotic disorders. I declare no competing interests. International incidence of psychotic disorders, 2002–17: a systematic review and meta-analysisWe found marked variation in incidence of psychotic disorders by personal characteristics and place. Some geographical variation could be partially explained by differences in case ascertainment methods. Full-Text PDF Open Access

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