City traffic in New York City may be linked to schizophrenia and mental health

City traffic does more than clog the air with exhaust and fill streets with noise. New research indicates that the way roads slice through neighbourhoods might also influence mental health, by making it tougher for residents to form and maintain social connections.

In New York City, the investigators observed that areas more physically fragmented by roads and traffic layouts also recorded higher numbers of hospital visits associated with schizophrenia.

The study was led by researchers at Brown University and builds on earlier work initially developed at the Columbia Mailman School of Public Health.

To do this, the team analysed mental health-related hospital visits across New York City ZIP codes and set those against a measure intended to reflect how isolated communities become because of road design, traffic flow, and poor pedestrian infrastructure.

More than a pollution problem

Plenty of past studies have already connected traffic-linked air pollution and noise with poorer mental health. This project, however, examined a different aspect of traffic.

Rather than concentrating solely on what vehicles emit, the researchers focused on what happens when roads themselves divide neighbourhoods.

What happens when motorways, heavily trafficked streets, and unsafe crossings reduce the ease of walking to a neighbour’s home, spending time outdoors, or feeling rooted in the area where you live?

This speaks to a sensation many people recognise but rarely have precise language for. Two communities can appear close on a map yet feel completely separate if one is pleasant to walk through and the other is split apart by fast-moving traffic.

“Imagine an environment where cars are present, but do not dominate, and that also has robust pedestrian traffic and walkable routes to neighbors’ homes, and where you can see kids playing outside and neighbors congregating to talk,” said Jaime Benavides, an expert in the Brown University School of Public Health.

“We wanted to home in on the road infrastructure that prevents people from interacting and learn how that influences their mental health.”

Disconnection in cutoff neighbourhoods

The researchers used annual counts from the New York State Department of Health for hospital visits associated with mood, anxiety, adjustment, and schizophrenia disorders.

They then compared those numbers with a metric known as the Community Severance Index.

This index was created to represent the extent to which a neighbourhood is physically and socially separated by roads, traffic, and missing basics such as pavements and pedestrian crossings.

The measure was developed under the direction of study co-leader Marianthi-Anna Kioumourtzoglou, now a professor of epidemiology and environment and society affiliated with Brown’s Center for Climate, Environment and Health.

The distinction matters because it shifts the focus from the familiar framing of traffic as pollution to something less visible, but potentially as consequential: traffic as a barrier that comes between people.

A road can link cities while still splitting a neighbourhood in two. Likewise, a street may carry thousands of vehicles and yet make everyday local life more difficult.

Community isolation, schizophrenia and New York City traffic

Living in urban environments has long been linked with elevated risks of anxiety, mood disorders, and schizophrenia. In this analysis, though, one result was more pronounced than the rest.

The strongest association emerged between community isolation and hospital visits related to schizophrenia.

Places that were more severed by road networks and traffic patterns generally saw more of these visits, and the relationship persisted even after the team adjusted for traffic-related air pollution.

That detail is significant. It implies the issue is not limited to the pollution generated by cars; it may also reflect how car-centred design reshapes day-to-day social experience.

The pattern also appeared broadly consistent across age groups, suggesting it is not confined to a single, narrow segment of the population.

The study did not claim to pin down the precise mechanism behind the link. Instead, it highlighted several plausible routes through which it could operate.

Problems due to road infrastructure

When a neighbourhood is boxed in by busy roads or has fragmented pedestrian routes, it becomes more difficult to navigate.

That can translate into fewer spontaneous encounters, less walking, less time spent outside, and fewer opportunities to build the informal social ties that can quietly support a sense of stability.

It can also add to stress. Having to cross hazardous roads, living with constant noise, feeling hemmed in, or struggling to reach shops and services can all grind down daily life.

Over time, environments like this may influence mental wellbeing in ways that are easy to overlook if attention stays fixed only on pollution levels.

The researchers note that mental health could be affected through multiple pathways, with isolation standing out as one of the most important.

Isolation may reduce physical activity, increase stress through fears about road safety, and limit contact between residents who might otherwise develop supportive, familiar everyday relationships.

This aligns with a broader, common experience beyond the boundaries of the study itself: people often feel better in places where walking is easy, meeting others is natural, and moving around does not feel like running the gauntlet of traffic.

Cars are not the whole answer

One of the study’s more striking implications is what it suggests about remedies.

For years, a prominent response to traffic-related harm has been the move towards electric vehicles. These results indicate, however, that switching the fleet may not address everything.

“We have increasing evidence that air pollution impacts mental health,” Kioumourtzoglou said.

“One of the solutions proposed is to move towards an electrified vehicle fleet. While this will result in reduced emissions, which is absolutely fantastic, what our study shows is that might not be enough.”

“We need to move away from car dependence and towards building healthier places and communities that bring people together instead of isolating them.”

That is a much larger task, because it goes beyond the type of car people drive and reaches into the fundamentals of how cities are designed and built.

Planning for connection

“While scientists are still researching the causes, prevention, and treatment of mental illness and mood disorders, urban environmental exposures – specifically, traffic patterns and road infrastructure – are things that can be addressed from an urban planning perspective,” Benavides said.

“Reducing vehicular traffic, creating more easily accessible parks and limiting highways and roads that cut through the middle of communities can improve collective mental wellbeing.”

The team now plans to extend the work by creating a version of their community isolation metric that could be applied in other major U.S. cities.

They are also preparing a new study examining how extreme heat, air pollution, and community isolation might combine to influence the mental health of older adults.

For the moment, the findings underline a straightforward but powerful point: a city can harm health not only through what it exposes people to, but also through what it prevents them from accessing.