The Hidden Toll of Mental Illness

When policymakers think about what causes morbidity and mortality, heart and other chronic diseases, cancer, and accidents often come to mind. Mental illness is rarely near the top of anyone’s list. But for those trying to make sense of the data — or design effective interventions — this omission can be dangerous.

Mental illness isn't just about isolated diagnoses like depression or anxiety; it is a pervasive driver of direct and indirect health outcomes, with consequences that ripple through the entire health care system and society at large. Yet our data systems, coding practices, and policy priorities routinely undercount its true impact.

Mental illnesses are deadly in their own right

Behavioral health disorders dramatically increase the risk of early death. A large meta-analysis estimated 2.22-fold increase in all-cause mortality among individuals with mental health conditions. Among these deaths, approximately 67% were due to natural causes such as cardiovascular disease, diabetes, or cancer, while about 17.5% were from unnatural causes, including suicide and accidents.

Mental illness fuels other diseases through biological and behavioral pathways

Mental illness does not operate in isolation. Depression, chronic stress, and anxiety contribute to a range of chronic illnesses through multiple pathways:

Behavioral: People with mental health conditions are more likely to smoke, abuse substances, eat poorly, and avoid exercise — all behaviors that sharply increase the risk of chronic illness and death.

Biological: Stress-related mental illnesses activate physiological systems that increase inflammation, disrupt hormone regulation, and impair immune function. These mechanisms raise the risk of cardiovascular disease, diabetes, neurodegeneration, and premature cellular aging.

Health care barriers: Individuals with mental illness often face reduced access to care (e.g., gaps in coverage, treatment delays), receive lower-quality treatment, and are less likely to get timely preventive services. These disparities are likely to worsen when the full effect of the so-called “Big Beautiful Bill” is felt. According to the Congressional Budget Office, nearly 7.8 million Medicaid enrollees will lose their coverage. Medicaid covers nearly one third adults with mental health disorders and one fifth of all adults with substance-use disorders.

An individual’s death certificate may list “heart disease” or “diabetes” as the official cause of death. But mental illness — or lack of access to treatment for it — may have contributed to the progression of that person’s chronic disease or prevented effective management of it.

Mental illness is the missing variable in many "non-mental health" tragedies

Perhaps most striking is the way mental illness contributes to death and injury in areas that are rarely coded or treated as behavioral health issues:

Road crashes: Depression, substance use, impulsivity, and stress increase the likelihood of impaired or risky driving. Road rage — often fueled by psychological distress — causes more than 1,000 U.S. deaths and thousands of injuries each year. Moreover, international reviews suggest that between 1.7% and 7.4% of fatal car crashes may be suicides, though many go unrecognized because it is difficult to prove suicidal intent. These links suggest that mental health’s role in road mortality is deeper than official statistics reveal.

Violence: Mental illness, especially when combined with substance use and lack of treatment, raises the risk of both perpetrating and being a victim of violence. Studies suggest that a significant portion of fatal police encounters involve individuals with untreated serious mental illness.

Maternal and child health: Mental health conditions, including suicide and overdose, are leading underlying causes of pregnancy-related deaths in high-income countries like the United States, accounting for a significant share of maternal mortality. Official maternal mortality statistics count only deaths of the pregnant individual, not those of the fetus or newborn. These deaths are frequently underreported due to gaps in mental health screening and cause-of-death attribution. Moreover, poor maternal mental health affects infant outcomes: Prenatal depression and substance use increase the risk of premature birth, low birthweight, and neonatal withdrawal syndromes. Children of parents with untreated mental health conditions also face higher risks of developmental delays, behavioral disorders, and psychological trauma.

These links are real, but many are under- or undocumented in routine health statistics. Most public health data attribute such deaths to their immediate cause without tracing the chain of events back to the mental health factors that made them more likely.

Count what counts

Mental illness is not just about feeling sad or anxious; it's a trigger that radiates through our entire health system, silently escalating risks, complicating diagnoses, and obscuring accountability. When we attribute deaths solely to "heart disease," "car accidents," or "overdoses" without recognizing the fundamental mental health factors that made these outcomes more likely, we misunderstand what's killing people.

This systematic undercounting leads to systematic underinvestment. By failing to connect the dots, we build policy silos — mental health funding on one side, and separate responses to chronic disease, traffic safety, and maternal mortality on the other. But these issues are interlinked, and our fragmented approach leaves millions vulnerable to preventable deaths.

For policymakers trying to understand why our health systems are overwhelmed and our interventions fall short, the answer may be the same as for any persistent headache: Look for the underlying stressors. Superficial fixes, like treating symptoms in isolation, won’t do. A more rigorous, evidence-based treatment plan must begin with a full accounting of the toll mental illness exacts across domains of health and safety. Only then can we prescribe real relief.

The prescription is clear: Count what counts. Only by recognizing mental health as a cross-cutting determinant of health — not just a standalone concern — can we design policies that address the root causes of our most pressing health challenges and finally provide the relief our communities desperately need.