The hurricanes in the Gulf and Florida over the last few weeks have left people displaced — and from more than just their homes. Places of worship, community centers, parks and schools are underwater, missing roofs or windows. And those losses can set the social infrastructure of a person’s life adrift. Years after the family is safe and the home is rebuilt, disaster victims could still be struggling with health problems that got a start because of the way a stressful, terrifying situation disrupted their lives. It’s even possible, some researchers say, that the stress and fear alone could create health problems later.

It’s easy to take social support systems for granted, but the role they play in reducing stress and keeping us healthy is crucial. When the federal Disaster Distress Helpline starts taking calls after an event like a hurricane, the requests it fields are less about direct let’s-talk-about-feelings therapy, and more about solving practical problems in survivors’ lives, said Maryann Robinson, chief of the Emergency Mental Health and Traumatic Stress Services Branch of the Substance Abuse and Mental Health Services Administration, which operates the service. There’s the Alcoholics Anonymous member trying to find a meeting that wasn’t flooded out. Or maybe a person with a much-needed prescription, but whose pharmacy was destroyed and whose doctor evacuated out of the state. If those workaday crises aren’t solved, they can start a chain reaction in the lives of survivors — a domino that carries the impact of the trauma far beyond the reach of a storm surge or gust of wind.

In some cases, these kinds of public health aftereffects have eclipsed the scale of the disaster itself. A 2005 World Health Organization report on the 1986 Chernobyl nuclear power plant accident found that the mental health impacts were proving to be a far bigger disaster for public health than radiation exposure. At that point, radiation had directly killed fewer than 50 people and was expected to eventually shorten the lives of an estimated 4,000. Meanwhile, the report concluded, 350,000 people had been forcefully displaced, suffered from public stigma, and believed themselves to be marked for death. The result, according to the report, was increased rates of fear, depression, poverty, alcoholism, unsafe sex and smoking. Chernobyl survivors often lacked access to high-quality medical and educational services, because it was difficult to recruit outside professionals to live in a community full of “tainted” people.

It’s easy to see how a disaster could cause long-term physical harm. In the case of Harvey, multiple industrial facilities released toxic pollution as a result of the storm and flooding, and some survivors were forced to wade through water contaminated by sewage and dangerous chemicals. When Irma hit the Caribbean, about 60 percent of the people on the island of Barbuda were left homeless and 95 percent of the buildings on the island sustained damage — which will probably mean lots of people exposed to mosquito-borne illness, mold and other factors that can cause physical problems down the line.

But it’s not always easy to predict the way a disaster will affect people’s health. Some impacts, particularly those tied to social support systems and the way people interact with their communities, can take years to become apparent. For instance, many of the people who were evacuated from New Orleans because of Hurricane Katrina had little control over where they were evacuated to, and few resources to get them back to New Orleans, or another city, later. Some of those people ended up in communities that were far less walkable than the ones they’d fled — less public transportation, more strip malls, no cohesive downtown. And so, by 2007, those people had higher body mass indexes than similar survivors who were relocated to walkable communities. Not exactly a public health risk you’d expect from a hurricane.

What’s more, it’s possible that the stress of experiencing a disaster — fear for your life, worry about how you’ll rebuild — and the chemical/emotional response that follows could itself cause harm. Some of the best evidence for this also comes from survivors of Hurricane Katrina. That’s because, two years before the storm hit, more than 1,000 New Orleans community college students enrolled in what was supposed to be a study of the support that single parents need to get through school. Researchers collected huge amounts of information on these people — about their health, their incomes, their living arrangements and more. After the storm, the study shifted gears, becoming the Resilience in Survivors of Katrina Project, comparing that baseline data to how people changed after the storm in order to learn more about the long-term effects of surviving a disaster.

Some of the RISK Project studies have found physical changes that are correlated with emotional distress. For instance, in one study, 15 percent of the people surveyed by the RISK Project had reported problems with headaches and migraines before the storm. Seven to 19 months later, when follow-up surveys were done, more than 56 percent of the same population reported those problems. What’s more, said Mariana Arcaya, a professor of urban planning and public health at MIT, her team found that the likelihood of experiencing migraines seemed to increase with the severity of post-traumatic stress disorder symptoms the person reported. And, having migraines before the storm wasn’t predictive of experiencing PTSD symptoms afterward — something that helps tease apart whether migraines were causing PTSD or the other way around. That doesn’t prove emotional distress caused migraines, Arcaya said. But the idea that what happens in your mind and emotions could affect your body doesn’t come completely out of left field. There’s a long history of literature associating post-traumatic stress disorder diagnoses with a wide variety of physical ailments. Various studies have reported increased rates of everything from dizziness and unexplained pain, to cardiovascular and gastrointestinal disorders in PTSD patients. On top of that, there’s increasing evidence that stress from things like acute poverty or abuse in early childhood can affect the way kids’ brains develop and change how their genes express certain traits. Scientists even talk about “John Henryism,” a hypothesis built on African-American health data suggesting that people forced to push against racism and other socioeconomic barriers on their way to success end up with worse health. “I think there’s a really exciting and growing science where, you experience something, that changes your psychological state and that changes your body,” Arcaya said.

Carol North, a crisis psychiatrist at the O’Donnell Brain Institute at the University of Texas Southwestern Medical Center, disagreed. Studies trying to find a link between emotional trauma and physical health are plagued by flawed methodologies, she told me. Most don’t have any information on survivors’ lives before the disaster, the way the RISK Project does, nor have they confirmed whether the physical damage being documented has a more obvious cause. For instance, she said, it’s possible emotional distress could trigger an inflammation response and cause a breathing disorder like asthma. But it’s much more likely that asthma was caused by breathing in mold.

But, whether stress responses in the body cause physical problems later or we’re merely dealing with a world in which the stressful impacts of a disaster alter behavior in ways that produce physical problems, reducing the stress still matters. Either way, it’s important to return people to some sense of normal life, helping them navigate basic tasks that have suddenly become infinitely harder, doing what we can to make sure their lives going forward aren’t worse. “What we’ve learned, and what many studies have shown, is to remove the stressor. To provide social first aid,” said Sandro Galea, dean of the Boston University School of Public Health. In the wake of a disaster, programs like the Substance Abuse and Mental Health Services Administration’s call-in line that helps connect people to daily life-restoring resources in their communities are probably crucial. “We need to create systems as soon as possible to return function, or prevent a loss of function,” he said. “That’s really medicine.”