Earlier this year, a truck driver known as “Maddog Trucker,” the owner of a popular trucking blog, took to his site to post some thoughts about road safety. This winter has been a particularly bad one for trucker wrecks, and Maddog was emotional:

The sad reality some Truckers have witnessed, and live with, is the screams they hear every night in [their] nightmares. Those screams are from a young child much like your own, pulled from the wreckage beside her dead mother killed by an ignorant Trucker that couldn't stop in time and crashed. No freight is worth your life and regardless of any situation, it's not worth going home in a body bag.

His words likely landed close to home for many readers. Around a third of the 3.5 million truck drivers in the U.S. will be involved in a serious road accident at some point during their careers. That’s a lot of people—more than a million—experiencing potentially severe job-related trauma. In fact, long-haul truckers have some of the highest rates of injuries and illness of all occupations—which makes it all the more alarming that truckers often have a difficult time accessing mental-health services.

Part of this has to do with the makeup of the trucking industry in the first place. Approximately 94 percent of drivers are men, according to the Bureau of Labor Statistics, and men are less likely than women to seek treatment for emotional distress. Research has also found that lower-income working-class Americans don’t seek mental-health care as readily as members of the middle and upper classes.

Even when truckers do want mental-health care, though, the demands of the job can make it impossible. For one thing, long-haul truckers are almost never at home—in some cases, they spend only a handful of days each year not on the road. They also tend to have very little control over their schedules. One trucker friend recently complained that, though she informed her dispatcher far in advance of the need to be at home for a crucial medical appointment, when that time came, she was still stuck out on the road and had to cancel the appointment. If acute care isn’t valued and made possible, mental-health care and preventive health care won’t be, either.

In the comments to Maddog’s post, several truckers empathized. Some expressed anger at “four-wheelers” for cutting in front of truckers to cause accidents. Others aired their frustrations with industry technology like e-logs, which require compliance with very rigid schedules, pushing truckers to make potentially dangerous decisions on the road in order to reach a destination on time.

No matter the cause, though, being involved in an accident can leave lasting mental scars. Being in a wreck—or even seeing one—can cause enough stress and anxiety to become a diagnosable mental illness, like acute stress disorder or post-traumatic stress disorder (PTSD). And with jobs that keep them away from their communities for such long stretches of time, many truckers lack the social support that could otherwise help them cope.

To make up for it, many truckers turn to social media: Facebook groups, Twitter conversations, and reading, writing, and commenting on blogs. Last month, for example, a member of the Facebook group “Women in Trucking” wrote that she had just witnessed a gruesome accident, and couldn’t get it out of her head. She asked other members how they dealt emotionally and practically with this relatively common experience. In a flurry of comments underneath, other truckers shared their own experiences with flashbacks, nightmares, and intrusive memories following traumatic incidents on the road. Several of them included the same refrain: The first one, they wrote, is the one that shakes you up the most.

Many truckers we spoke to describe feeling haunted when they are near the scene of a particularly gruesome accident, or when they see another driver engage in a behavior that previously led to an accident. Exhaustion can compound these issues, and the job often offers little relief—truckers are regularly pushed into difficult circumstances while on the road. They may speed, for example, if shift limitations meant they would have to stop driving within the hour, but they’re more than an hour away from a safe, legal space to park and rest. And truck stops and rest areas can fill up, meaning that some truckers who need to stop driving—because of duty limits, or because they’re too tired to continue—are forced to just keep going.

The job of a trucker, in other words, can mean dealing with PTSD, regularly facing trauma triggers, and battling exhaustion through it all—without professional help to identify or manage these mental-health problems. This isn’t just dangerous to the truckers; it can be a safety hazard for anyone on the road. The most common symptoms of PTSD include difficulty sleeping, difficulty staying awake, panic attacks, and problems concentrating. If a number of American’s 3.5 million truckers have these symptoms, it’s a public-health issue for all drivers.