When Brian Cox got his driver's license at 16, his parents wouldn't allow him to have passengers in the car until he had clocked 5,000 safe miles behind the wheel.

Kevin Snyder's parents made him drive with them for 21 consecutive days without the slightest infraction before they allowed him to apply for his license. Any time he looked away from the road to change a radio station, for example, his parents pushed him back to Day One. It took him two years to graduate from learner's permit to full license.

Both teens' parents had worries beyond those that most parents have when their children start to drive: Brian and Kevin have attention-deficit hyperactivity disorder (ADHD).

Studies indicate that young people with the disorder, who often find it difficult to concentrate and are more prone than others to impulsive behavior, have abnormally high rates of traffic violations, accidents and instances of driving without a license. One study, funded by the National Institute of Child Health and Human Development and published in July, reported that of 105 people with ADHD who were studied, about 20 percent had had their license suspended or revoked -- the same number who had received 12 or more traffic citations or had caused more than $6,000 in damage in their first crash. Those figures are two to four times the norm for young adults. In addition, about 25 percent of them had been involved in three or more crashes -- a rate seven times higher than normal.

For those familiar with the disorder -- an estimated 3 to 7 percent of school-age children have it, with perhaps half of them continuing to be affected into adulthood -- those statistics likely are not terribly surprising. Larry B. Silver, a clinical professor of psychiatry at Georgetown University Medical Center who specializes in treating ADHD, puts it plainly: "Those who are distractible may be paying attention to things other than driving."

This suggests that many parents of teens with ADHD should pay particularly close attention to their child's driving.

"We did a lot of road riding with Brian," says his father, Daniel Cox. "We were vigilant about his inattention. [Still,] the first time I took [Brian] out, he pressed the accelerator instead of the brake at a stop sign. On the highway, [I caught him with] his whole head down when changing the radio station."

Those early mistakes were hardly unexpected. Cox had started to prepare Brian for driving long before he got his learner's permit.

"We knew it was coming," Cox says. "We talked about it, we set up steps."

Marlene Snyder, Kevin Snyder's mother, has a similar story: "We started talking to Kevin in second grade about consequences [involved in driving]." She also talked with him about his ADHD. She wanted to be certain that he understood it and its implications for driving -- and to prepare him for the possibility that he might not start to drive when his friends did. For many children with ADHD, says John Pleasant, a Washington-based clinical social worker, the disorder brings with it "a sense of shame and embarrassment . . . of feeling different and angry. . . . For kids old enough to drive, there has been a long-term wrestling with that."

Snyder agrees. "Kids don't want to be different from other kids," she acknowledges sympathetically. For her, though, it's a safety issue. "It's a horrible experience, going to a teenager's funeral," says Snyder, who believes ADHD was a factor in several accidents that have left acquaintances dead or seriously injured.

It falls to parents to help their child to understand and accept the disorder -- "not like it," says Pleasant, "accept it" -- and to take charge of it.

Cox took a novel approach to doing that with his son: He not only talked with Brian about the disorder and safe driving; he also encouraged him to study the subject. When Brian was 14, he built a rudimentary driving simulator and entered it in a statewide science fair in Virginia. He won a first-place award.

If the attention that Daniel Cox and Marlene Snyder paid to driving and ADHD seems unusual, it may be because they are drawing on professional experience. Snyder, an education consultant specializing in ADHD-related issues, has written a book called "ADHD and Driving: A Guide for Parents of Teens with ADHD." Cox, a professor of psychiatric medicine and the director of the Behavioral Medicine Center at the University of Virginia, has researched the relationship between driving and such diseases and disorders as alcoholism, Alzheimer's and diabetes. Now, his focus is on driving and ADHD. Both of his sons -- Brian and younger brother Cory -- have the disorder.

"Seeing them grow up got me focused on that," he says.

For both Cox and Snyder, one rule was paramount for their teens once they started to drive: Take your medicine or you can't take the car. Recent drug studies, some conducted by Cox, are giving new strength to that advice.

First Line of Treatment

Stimulant medications such as Ritalin are the most frequent first line of treatment for ADHD. They have been prescribed for more than 50 years and are overwhelmingly regarded as safe for adults and children aged 6 and older who have properly diagnosed ADHD. (See "Family News," Page F4, for an update on a new stimulant drug.)

"Ritalin is a specific drug for a specific disorder," says Cox, whose own research on Ritalin, conducted in 2000, showed evidence that Ritalin improved the driving of college students with ADHD. Comparing seven students with ADHD to six without, his study found that "there was no difference between ADHD and non-ADHD subjects while on Ritalin."

More recently, Cox compared the driving behavior of young adults on Ritalin to those taking a newer drug, Concerta. Both are methylphenidate-based stimulants; however, Concerta is a long-acting drug that requires a single daily dose, while Ritalin must be taken two to three times a day. The results of that second study, which was funded by McNeil Consumer and Specialty Pharmaceuticals, the maker of Concerta, suggest that those taking the longer-acting stimulant will drive consistently more safely during a given day than those on shorter-acting drugs.

As Cox pointed out in the first study, "A major limitation with Ritalin is its short half-life. If a driver takes the medication twice a day, at breakfast and lunch, there would be no medication in the bloodstream at one of the high accident times, the 5 to 6 p.m. rush hour." There is also a significant lag period between doses, during which symptoms can return in force. Drivers on Concerta, Cox found, did not have this problem: "One of the unanticipated events was the consistency of the [Concerta] subjects over time," he says. "Their driving behavior at 11 p.m. was the same as at 2 p.m."

Both studies conducted by Cox were small, a limitation that he acknowledges. Still, they are significant -- not only for what they suggest but also for the fact that they are being done at all. Until 10 years ago, the relationship between ADHD and driving risks had gone largely unnoticed.

Studying the Problem

In the early 1990s, on a visit to a rehabilitation center in Milwaukee, Russell Barkley walked past a lab in which the driving skills of elderly people were being measured. Using baby-toy steering wheels connected to a computer, researchers gathered data on critical abilities such as reaction time and problem-solving. Barkley had recently read a Canadian study suggesting a rate of traffic violations and accidents among ADHD drivers that was four times the norm. That study piqued his curiosity. Those flimsy steering wheels gave him an idea.

"I looked around at the lab," Barkley recalls, "and said someone should do this for ADHD."

Not everyone agreed. On his return to the University of Massachusetts, he found little interest among his colleagues in psychiatry and psychology. To him, though, the idea was new and exciting: "No one had done this."

Now at the Medical University of South Carolina in Charleston, Barkley was until recently the director of psychology and a professor of psychiatry and neuropsychology at the University of Massachusetts; he also founded the university's clinics for children and adults with ADHD.

Barkley began his driving research by attempting to confirm the Canadian findings in a study he conducted in Milwaukee. Surveys submitted by parents of teens with ADHD, as well as by parents of teens who did not have the disorder, revealed a tremendous number of accidents and traffic violations among the former group. During the three- to five-year period covered by the surveys, nearly a quarter of the 44 teens with ADHD had had their licenses suspended or revoked, and the ADHD drivers were involved in 54 crashes. In a control group of 37, only 16 cashes were reported a crash during the same period.

"We replicated the Canadian study," Barkley says of his research, the results of which were published in 1993, "but we also saw that it was worse than we had imagined. Their knowledge of the rules of the road was normal -- they just didn't know how to apply them.

"At that point we realized it was a scary problem."

According to Barkley, that first study was crudely done. He wanted to use sophisticated driving simulators and he wanted to evaluate driving behavior on the road. So he hired driving instructors to ride with both ADHD teens and a control group of other young drivers. The teens with the disorder became easily frustrated, and their emotions were closer to the surface as they drove, the study found. The data, as it accumulated, began to paint a frightening picture.

"Our driving instructors found that [ADHD teens] wouldn't wait at stop lights, they cut people off, they drove on the shoulder and ran lights." Two of the instructors quit the study -- they didn't feel safe.

Barkley recalls: "If it had not been a study, they said they would have sought revocation of the [ADHD teens'] driver's licenses."

Barkley now realizes he shouldn't have been shocked by what his studies revealed: "In hindsight, it doesn't surprise me, but no one was interested then" in the impact of ADHD on driving performance, he says. "At the time nobody cared, nobody looked, nobody knew."

Parents in Control

Now, as a result of studies like those conducted by Barkley and Daniel Cox, that has begun to change, at least among researchers. And Marlene Snyder hopes to bring the research findings to parents, along with her guidelines for reducing risks on the road. In the 20 steps she offers in her book, the stress repeatedly falls on parental involvement. That involvement, she emphasizes, has to begin before the teen starts to drive:

"Parents have to talk really early. The best time to think about responsibilities is before your teen gets behind the wheel."

More than just talk, though, parents must model safe driving behavior -- using the side view mirror and signaling before changing lanes, coming to a complete stop at stop signs, observing speed limits. School-based driver's education programs, she writes, "should be treated as an excellent supplement to your own driver education efforts."

"Kids with ADHD are often behind [other kids] in age maturation," she points out. "Parents have to honestly observe their kids -- do I feel safe [when I am riding with them]?"

And if they don't? "They have no business allowing them to drive."

Of course, the same could be said of the parents of any teen. As Daniel Cox stresses, "There are all sorts of conditions out there that affect driving: sleep apnea, diabetes requiring insulin. . . . What I want to point out is ADHD is not unique in making driving dangerous."

Brian Cox, 19, and Kevin Snyder, 25, have been driving for a few years. With supportive parents and the right medication ("No medication, my son doesn't drive," says Daniel Cox, who notes that Brian keeps some Ritalin in his car in case his dosing routine is interrupted), each has learned to drive safely.

Cox laughs when asked about his 14-year-old, Cory, but his trepidation is plain. Cory really wants to drive.

"He gets to get in and start Brian's '66 Mustang every night," Cox says.

But father and son have already started talking about the day, and the conditions, when Cory will start driving. He'll be prepared.

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Matt McMillen last wrote for Health about adults with ADHD and his own experience with the disorder.