Diagnosis of any mental disorder significantly increased the risk for all other mental disorders, based on data from a population-based cohort study of almost 6 million individuals followed for nearly 84 million person-years.
Comorbidity among mental disorders has been acknowledged, but comprehensive data on comorbidities across all subsets of disease and a comprehensive risk assessment has been lacking, wrote Oleguer Plana-Ripoll, PhD, of Aarhus University in Denmark, and his colleagues.
In a study published in JAMA Psychiatry, the researchers included all individuals born in Denmark between Jan. 1, 1900, and Dec. 31, 2015, who were living in Denmark between Jan. 1, 2000, and Dec. 31, 2016. They used national health registries to identify mental disorders, and diagnoses were based on the International Statistical Classification of Diseases and Related Health Problems. The study population included 2,958,293 men and 2,982,485 women with an average age of 32 years at the start of the follow-up period; participants were followed for a total of 83.9 million person-years. Mental disorders were categorized in groups, and groups were paired for risk assessment.
Overall, the risk of developing all other mental disorders increased with the diagnosis of one mental disorder, most prominently in the first year after diagnosis, but the risk persisted for at least 15 years. In one model controlling for age, calendar time, and sex, hazard ratios ranged from 2.0 for prior intellectual disabilities paired with later eating disorders to 48.6 for prior developmental disorders paired with later intellectual disabilities.
The large sample size allowed for focus on absolute risk and the study was accompanied by an interactive website (http://www.nbepi.com) that allows clinicians (and potentially patients) to monitor possible emerging mental health comorbidities.
As one example of absolute risk assessment, the researchers determined that 40% of men and 50% of women diagnosed with a mood disorder before age 20 years would develop an incident neurotic disorder as defined by the 10th revision of the International Statistical Classification of Diseases and Related Health Problems within the next 15 years. “The provision of absolute risk estimates may facilitate the clinical translation of our findings, and lay the groundwork for future studies related to personalized medicine and the primary prevention of comorbidity,” Dr. Plana-Ripoll and his colleagues wrote.
The researchers acknowledged the study’s limitation of comorbidities to pairs of disorders versus three or more, the use of groups of disorders rather than specific disorders, and the limitation to mental disorders treated in secondary care settings. However, and the comprehensive nature of the analysis will provide an important foundation for future research,” they said.
The research was supported by the Danish National Research Foundation. Dr. Plana-Ripoll had no financial conflicts to disclose. Some coauthors disclosed grants from the National Institutes of Health, Novo Nordisk Foundation, and the European Research Council, and some coauthors disclosed financial relationships with Sanofi Aventis, Johnson & Johnson, Sage Pharmaceuticals, Shire, and Takeda.
SOURCE: Plana-Ripoll O et al. JAMA Psychiatry. 2019 Jan 16. doi: 10.1001/jamapsychiatry.2018.3658.