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People with attention deficit hyperactivity disorder are twice as likely to die earlier than those without the condition — and the causes tend to include freak accidents and car crashes, researchers reported Wednesday.

In the first study of its kind, published in The Lancet, Danish scientists found that the risk for premature death for those with ADHD increases with age.

People diagnosed at 18 or older were more than four times likely to die young, compared to the general population. And, startlingly, the death rate for women with ADHD was about double that of men with the disorder.

Many who suffer from the inattention and impulsivity of the disorder can speak intimately about its inherent risks.

Bronkar Lee, an entertainer from Los Angeles who was diagnosed with ADHD, said he nearly died in high school when he crashed his car — he was distracted, he said, while eating a cheeseburger.

“I took a bite and the next you know — boom — I drilled the back end of a car, and my head was stuck in the windshield,” Bronkar, now 35, told NBC News.

Bronkar Lee and his wife Cyndi, whom he calls his "sanity goddess" for keeping his impulsive behavior under control. Courtesy of Bronkar Lee

His diagnosis came in seventh grade. “I was totally out of control, the class clown,” he said. “I was focused on other people in ways that had nothing to do with the task at hand.”

Another person with ADHD, Liz, a mother of two from Washington, D.C. , said the disorder has wreaked havoc in her family. Both she and her brother were diagnosed in their 40s.

“I used to have physical accidents a lot, falling down stairs, not watching where I was going as I was ‘dreaming’ as a child,” said Liz, 62, who asked that her last name not be published for privacy reasons.

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“My 26-year-old daughter is all over the place — lots of speeding tickets and accidents,” she added. “My son, who is almost 30, has had a wicked time with ADHD. He was a difficult child, got into a lot of trouble as a teenager and had relationship problems.”

Previous studies have shown that those who have ADHD often are challenged by schoolwork and jobs, but this Danish study is the first to show a greater risk for a younger death from “unnatural causes.”

“ADHD is often debated and criticized, but our study points to the fact that it’s not something to be taken lightly,” said Dr. Soren Dalsgaard, lead investigator from Aarhus University in Denmark. "I hope this will contribute to the other overwhelming evidence that this is a true disease.”

Dalsgaard studied nearly 2 million people from the Danish national register. Looking at individuals’ medical records from age 1 to 32, he and colleagues compared causes of death in those diagnosed with ADHD and those without the disorder.

Of the 32,000 people who had ADHD, 107 had died, and most of those perished from accidental causes. Researchers ruled out other factors known to cause premature death, including age, sex, family history and psychiatric disorders.

ADHD, which is characterized by distraction and risk-taking, can make a person more accident prone and at higher risk for death from “unnatural causes,” according to the study.

“It’s not surprising,” Dalsgaard said. “It corresponds to impulsivity.”

Michael, a 50-year-old advertising executive who asked that his last name not be published, said the study makes sense, adding that seeking treatment for ADHD, at age 35, “saved my life.”

“I almost lost my career,” he said. “If I had been diagnosed earlier, I would have been retired by now. I missed huge opportunities. I was driven to distraction.

“My impulsive behavior showed up in business, making stupid and rash decisions,” Michael said. “My mind moved so fast I had no ability to control my emotions. I couldn’t stop, think and listen.”

About 5 percent of all Americans have ADHD, according to the Centers for Disease Control and Prevention.

The neurodevelopmental disorder can be managed with a combination of behavioral therapy and medications, experts say.

Boys are diagnosed at twice the rate as girls, who tend to be less disruptive.

“One explanation is girls and women may have a more serious type of ADHD than males,” Dalsgaard said. “But symptoms are not so obvious in females. They are more restless and have pronounced daydreaming.”

The study also noted that those with ADHD are more likely to have co-existing conditions — oppositional defiant disorder, conduct disorder, or substance use issues — that further boost the risk for serious mishaps eight times higher when compared to peers without ADHD.

Bronkar Lee said he was prone to addiction — formerly cigarettes. And ADHD patient Michael said his friends with the disorder used illegal substances to self-medicate.

In recent years, critics have questioned whether too many American children were being diagnosed and over-medicated for ADHD. Some, like Liz, who refuses to take drugs, worry that this study will needlessly increase diagnoses.

But ADHD experts disagree.

Dr. Lenard Adler, professor of adolescent and child psychiatry and director of the Adult ADHD Program at NYU Langone School of Medicine, said leaving the disorder untreated, “carries a high burden.”

“Untreated symptoms get greater over time,” Adler said. “We want the right diagnosis made for the right people.”