In a Danish population-based cohort study of almost 6 million people, researchers found that individuals with any mental disorder were at increased risk for comorbid mental disorders.
Although the risk for comorbidity was highest in the first year following mental disorder onset, the risk persisted over at least 15 years, according to data published in JAMA Psychiatry.
“To date, to our knowledge, register-based studies of comorbidity have been restricted to subsets of mental disorders,” Oleguer Plana-Ripoll, PhD, from the National Centre for Register-based Research, Aarhus University, Denmark, and colleagues wrote. “There is a need to examine the comorbidity of mental disorders in a comprehensive fashion.”
The investigators conducted a comprehensive study of comorbidity within mental disorders using data from Danish health registers. They provided temporally ordered age- and sex-specific pairwise estimates between the major groups of mental disorders to examine the link between all 90 possible pairs of disorders. In addition, they compared the rate of diagnosis with a specific later disorder between those who were exposed and unexposed to other prior disorders.
The study included data from 5,940,778 people followed up for 83.9 million person-years. Overall, receiving a diagnosis of any one mental disorder increased the risk for a later diagnosis of other disorders. When controlling for age, calendar time and sex, HRs ranged from 2 (95% CI, 1.7-2.4) for prior intellectual disabilities and later eating disorders to 48.6 (95% CI, 46.6-50.7) for prior developmental disorders and later intellectual disabilities, analysis showed.
People with any mental disorder were at increased risk for having comorbid mental disorders, according to a large Danish population-based cohort study.
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Plana-Ripoll and colleagues also found that the HRs for the onset of each type of subsequent disorder had a temporal pattern, and estimates were higher in the first year after onset. However, they observed persistently elevated rates over the observation period (15 years).
Furthermore, some disorders were linked to substantial absolute risks of developing specific later disorders, according to the results. For example, 30.6% (95% CI, 29.3-32) of men and 38.4% (95% CI, 37.5-39.4) of women diagnosed with a mood disorder before age 20 years developed neurotic disorders within 5 years.
Researchers also developed an interactive website to visualize all results and guide future research, available here: http://www.nbepi.com
“If clinicians and individuals with mental disorders had ready access to diagnosis-, age-, and sex-specific absolute risks of potential future comorbidity, this information could permit more tailored interventions and better education about self-management,” they wrote. “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.”
These findings, along with findings from family, twin and molecular genetic studies, signify “an exciting time for psychiatric research, with opportunities to develop new and more successful approaches to classifying mental disorders,” Steven E. Hyman, MD, from the Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, wrote in a related editorial. However, challenges remain.
“The recognition of shared underlying factors does not identify them at a useful level of specificity, nor does it turn them into actionable biology or cognitive frameworks for prevention and treatment. ... We know that there are important developmental and environmental risk factors that must not only be identified but understood mechanistically along with biological clues,” Hyman wrote. “Indeed, if research is to advance the laudable desire of the authors to contribute to prevention of new incident diagnoses, Plana-Rapoll et al have helped their cause by pointing out that we must make diagnoses in a new way.” – by Savannah Demko
Disclosure: Hyman has received personal fees for serving on the scientific advisory boards of BlackThorn Therapeutics, FPrime Capital Partners and Janssen, and personal fees for serving on the board of directors of Q-State Biosciences and Voyager Therapeutics. Plana-Ripoll reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.