Mental illness in young individuals is associated with a strikingly high risk of subsequent physical illness, disability, and premature mortality, results of a large longitudinal study show.
Investigators analyzed 30 years of hospital data on more than 2.3 million individuals and found that those diagnosed with a mental disorder were more than twice as likely to develop a subsequent physical disease at a young age, and almost four times as likely to die at a younger age compared with their counterparts without psychiatric illness.
“Our findings indicate that mental disorders in young people aren’t just signs of mental health problems, they are also early-warning signs of later physical health problems,” lead author Leah Richmond-Rakerd, PhD, assistant professor, Department of Psychology, University of Michigan, Ann Arbor, told Medscape Medical News.
“Greater integration of mental and physical health treatment, particularly in early life, could have long-run benefits,” she added.
The study was published online January 13 in JAMA Network Open.
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Although previous research provides “important information about the associations between mental and physical health,” most studies used end-of-life measures of poor physical health or relied on cross-sectional designs, follow-up periods of less than 15 years, or retrospective reports, the authors note.
To address these gaps, the researchers used population-wide administrative data drawn from the New Zealand Integrated Data Infrastructure to analyze potential associations between mental disorders and physical health in 2.3 million New Zealand citizens between the ages of 10 to 60 years at baseline.
Subjects were born between January 1, 1928 and December 31, 1978 and were divided into age groups based on decade of birth. The population was evenly divided between males and females (50.7% male).
The researchers studied nine “broad categories” of mental disorders: substance use, psychotic, mood, neurotic, physiological disturbance, personality, developmental, behavioral, and unspecified, as well as self-harm behavior.
They also collected information about eight chronic physical diseases: coronary heart disease (CHD), gout, chronic obstructive pulmonary disease (COPD), diabetes, cancer, traumatic brain injury (TBI), stroke, and myocardial infarction (MI). Information about mortality was obtained through records of the New Zealand Department of Internal Affairs.
Physical Disease Overrepresented
During the 30-year observation period, 20% of individuals were admitted to public hospitals for a physical disease, whereas 4.4% were admitted for a mental disorder.
Physical diseases were “overrepresented” among individuals with a mental disorder, with 31.9% of those with a mental disorder also experiencing a physical disease during the observation period, compared with the 20% of the population-wide prevalence of physical disease.
Overall, men were more likely than women to be diagnosed with a physical disease. On the other hand, similar or identical numbers of men and women were diagnosed with a mental disorder. There was also a higher percentage of younger vs older people diagnosed with a mental disorder.
Mortality was more likely to occur in those with a physical disease (relative risk [RR], 4.12; 95% CI, 4.08 – 4.15; P < .001) and to occur at a younger age, compared to those without a physical disease or mental disorder (hazard ratio [HR], 4.69; 95% CI, 4.65 – 4.73; P < .001).
Strikingly, the researchers found an increased mortality risk and faster time to death in individuals with a mental disorder, compared with those without a physical disease or mental disorder (RR 3.39; 95% CI, 3.32 – 3.47, and HR 3.80; 95% CI, 3.72 – 3.89, respectively; P < .001 for both).
“Among individuals who died, the average number of years lived per person was 1.1 years shorter among those with a mental disorder compared with those without a mental disorder or physical disease,” the authors report.
They note that the associations were observed in both genders and in all age groups, although a stronger association was found between mental disorders and mortality in the youngest vs the oldest cohort.
“Among individuals with a physical disease, those with a mental disorder developed the physical disease at an average of 2.0 years earlier than those without a mental disorder,” the authors reported. The HR of developing physical diseases at younger age was 2.33 (95% CI, 2.30 – 2.36).
Individuals with a mental disorder had more hospital admissions, longer hospital stays for physical problems, and incurred higher governmental costs for the treatment of physical diseases, compared with those without a mental disorder; in fact, the lifetime healthcare costs per person were 12.2% higher among those with a mental disorder.
Even after accounting for preexisting physical illnesses, sex, and age, the associations remained across all different types of mental disorders and self-harm behaviors.
“The connection between mental disorders and subsequent physical disorders might be due to a range of factors,” said Richmond-Rakerd. “For example, people with mental health problems might have difficulty accessing good healthcare and difficulty implementing health behaviors [or] mental disorders might also have a direct effect on physical health.
“Importantly, we found that the association was not disorder-specific and individuals diagnosed with different types of mental disorders all developed excess physical illnesses, which suggests some common mechanisms.”
The findings also “suggest that targeting any mental disorder in early life — not just a particular few — could benefit later-life health.”
Youth a “Neglected Risk Factor”
Commenting on the study for Medscape Medical News, Patrick McGorry, MD, PhD, professor of youth mental health, University of Melbourne, Australia, said, “young people in transition need proactive, expert help navigating the transition to adult life, especially now, because the mental health of young people has been deteriorating and the effect of COVID-19 will lead to greater deterioration.”
McGorry, who was not involved with the study, said that although the “peak time for developing a mental disorder is in the teens and early adulthood,” it is a “neglected risk factor” for adverse outcomes, both physical and mental.
Richmond-Rakerd noted that clinicians who treat mental health disorders in young people might also be well positioned to help prevent physical diseases in later life. “For instance, mental health providers could deliver psychoeducation to clients about their risk of developing physical diseases, and incorporate health-behavior-change interventions into their work,” she said.
This research was supported by grants from the National Institute on Aging and the UK Medical Research Council. Additional support was provided by National Institute on Aging through the Duke Population Research Institute, the National Institute of Child Health and Development through the Duke Population Research Center, and funding from the Jacobs Foundation. The study authors and McGorry have disclosed no relevant financial relationships.
JAMA Network Open. Published online January 13, 2021. Full text