I’ve been told that having one’s child begin their driving career is a parent’s worst nightmare under the best of circumstances. Fortunately, I don’t have to deal with this myself for a few more years - can’t wait. For parents whose child has ADHD - or at least significant levels of attentional difficulties - these concerns can be even greater. The thought of having their inattentive, impulsive child behind the wheel of a car is something that many parents, whom I have worked with, have described as “nerve wracking”.

What do we know about the relation between ADHD symptoms and driving difficulties in adolescents/young adults? Is this as bleak a circumstance as many parents imagine? This was the focus of a very interesting study that appeared recently in the Journal of the American Academy of Child and Adolescent Psychiatry (Woodward, L.J., Fergusson, D.M., & Horwood, J. (2000). Driving outcomes of young people with attentional difficulties in adolescence. JAACP, 39, 627-634).
Participants in this study were 1265 New Zealand children who had been followed from birth into young adulthood. (This is obviously an enormous undertaking and many, many issues besides the topic of the current report were examined using this cohort of children). For this study, the researchers obtained parent and teacher reports of children’s attentional difficulties and hyperactive behaviors when they were 13 years old and created a score for each participant by averaging the parent and teacher ratings. Then, children were placed into one of five groups based on the severity of their “attention problems” score. So, only a small percentage of the 1265 children would have been considered to have ADHD.

Driving outcomes for these individuals were obtained when they were 21 based on detailed interviews with each participant. >From the original sample of 1265 adolescents, 941 were interviewed about their driving history at age 21. Three different types of adverse driving outcomes were inquired about.
First, participants were asked whether they had been involved in an accident that resulted in an injury (5% of the total sample had) and/or no injury (38% of the sample had).

Second, participants were asked about whether they had engaged in drinking and driving. This included questions about whether they had ever driven a motor vehicle while drunk (26% said they had), while seriously intoxicated/very drunk (10% said they had), or ever been arrested on a drunk driving charge (5% said they had). In addition, 10 other questions related to drinking and driving were asked and an overall “drinking and driving” score was computed based on each participant’s response to these items.

Finally, participants were asked about their history of traffic violations. For each year between 18 and 21, participants were asked whether they had ever: 1) driven without a license (14%); 2) driven without a proper vehicle registration (40%); or 3) participated in street racing (10%). In addition to these items, an additional set of items pertaining to dangerous driving behavior (e.g. speeding, driving through a red light) were also asked about, including questions about the frequency of such dangerous driving habits (choices ranged from never to nearly every day).

The basic question of this study is whether high levels of ADHD symptoms at age 13 - as indicated by the combined parent and teacher ratings - predicts more adverse driving outcomes during the 18-21 year age period. Due to the fact that ADHD often occurs in the context of other difficulties (e.g. conduct problems), which can possibly account for any relationship between ADHD symptoms and poor driving outcomes, it is important for a study like this to try and control for this possibility.

Fortunately, the authors were careful enough to do this. Thus, in addition to ratings of ADHD symptoms for all participants at age 13, they also collected data on other characteristics that could be related to young adult driving outcomes including conduct problems (also based on parent and teacher ratings), IQ, and, of course, gender. In addition, data was collected on measures of parenting and family functioning (e.g. maternal disciplinary style; child’s exposure to parental separation, divorce, or death). Social background characteristics were also used to provide an indication of the child and family’s standard of living.

The last piece of information collected dealt with each individual’s driving experience at age 21. Specifically, each young adult was asked about the number of months he/she had held a driver’s license of any kind as well as their estimate of the total distance they had driven. This is important because those who had driven more would have greater opportunity to get into an accident.

RESULTS

So, do ADHD symptoms at age 13 predict more adverse driving outcomes in young adulthood? The answer is not quite as clear-cut as you might expect.
The authors first compared driving outcomes for the sample divided into the 5 groups that ranged from very low to very high on the ADHD symptom ratings at age 13. In this analysis, no attempt was made to control for the other factors (e.g. conduct problems, family environment) that they had thought might be important.
When examined in this way, the results are striking: on every single driving outcome measure, subjects in the highest ADHD symptom group look worse than those without such problems. For example, those in the highest group were:

In general, the pattern seemed to be one of increasingly adverse driving outcomes across the 5 groups. From this perspective, it would appear that ADHD symptoms do, in fact, predict a wide variety of problematic driving outcomes and that parents’ concerns about their ADHD child and driving are well-founded.
Next, however, the authors examined these same outcomes across the 5 groups after all the other factors they had collected (e.g. conduct problems, IQ, family environment factors, driving experience) were taken into account. What this type of analysis enables one to learn is what is the independent contribution of age 13 ADHD symptoms to young adult driving difficulties after all these other characteristics have been accounted for. This tells you, in essence, whether poor driving outcomes can be explained by the independent contribution of ADHD symptoms to driving difficulties, or whether the predictive relationship that was found really occurred because of these other factors. For example, we know that ADHD and conduct problems often co-occur. One can also imagine how children with serious conduct problems, regardless of whether they also have ADHD, might be destined to become dangerous drivers. If this is true, then children with ADHD and conduct problems would be found to have poorer driving outcomes, but this might be entirely because of the conduct problems and have nothing to do with the child’s ADHD. In such a case, concluding that ADHD predicts poor driving in young adulthood would be erroneous.

So, what did this more sophisticated analysis yield?

For the most, part, it appears that the independent contribution of ADHD symptoms to young adult driving difficulties is relatively modest. Overall, for 8 of the 11 driving outcome measures considered, ADHD symptoms at age 13 no longer predicted poorer outcomes after controlling for other relevant factors. The 3 outcomes that continued to be predicted by ADHD symptoms were driving without a license, general traffic violations, and risk of a motor vehicle accident involving injury. In addition, it was only the latter outcome that remained significant after appropriate statistical corrections were made. Involvement in a motor vehicle accident that results in injury is, of course, a very important outcome. In fact, one could reasonably argue that it is the most important outcome of all those that were considered.
If ADHD symptoms did not independently predict the vast majority of adverse driving outcomes, what factors did? This varied somewhat across the different outcomes, but in general:

Here is something I found particularly interesting. Overall, those with the highest ADHD scores at 13 reported having their license for the least amount of time - almost a year less on average than those in the low attention problem group - but also reported having driven the greatest distance - about 30% more than the low attention problem group.)

Summary and Implications

Although this study reveals difficulties in attempting to associate ADHD symptoms and driving problems, the sobering conclusion that remains is that ADHD symptoms during young adolescence does dramatically increase the risk of being involved in an injury producing motor vehicle accident during young adulthood. In fact, after controlling for a number of possible confounding factors, those in the highest ADHD symptom group were over 4 times more likely to be in such an accident than those in the low group (14% vs. 3%) and twice as likely as those in the moderate group (14% vs. 7%). Parental caution and concern is thus quite warranted. When high levels of ADHD symptoms are combined with being male, having significant conduct problems, and spending extensive time driving despite relatively limited experience, the risks of involvement in a serious accident increase substantially.

No specific recommendations for dealing with this concern are provided in this paper. However, doing one’s best to make sure that their young adult child’s ADHD symptoms are being managed well should reduce the risk of driving difficulties. This can be quite a challenge, however, when one’s “child” is an independent adult who may refuse and deny any appropriate interventions. I wish I had some answers here, but I don’t - this is just a difficult issue that probably depends a great extent on how well a child’s condition has been managed and discussed over many years.

One limitation of this study is the authors did not differentiate the driving risk that accrues from inattentive vs. hyperactive impulsive symptoms. It is easy to imagine how both types of problems would contribute to serious motor vehicle accidents, but it would have been very nice if the authors had been able to evaluate the relative contribution of each type of symptom.

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