by Chuck Ruby, Ph.D.

The results of a study, published in JAMA Pediatrics, claims that ADHD causes an increased risk of automobile crashes. I'll explain why this is a trivial conclusion. What's more, it is absurd that the authors suggest more research into “the specific mechanisms by which ADHD influences crash risk to develop effective countermeasures.” ADHD is not a disorder that causes anything. ADHD is a label that describes a constellation of behaviors. To say it is a disorder that causes an increased risk of crashes is like saying walking is a disorder that causes an increased risk of moving.

If we look at the definition of ADHD contained in the DSM, we find that it consists of an arbitrary checklist of items about not paying attention and not inhibiting impulses. It has nothing to do with brain dysfunction. There are no laboratory tests to detect it. It has nothing to do with pathology in the person. It describes people who do not pay attention, not people who can’t. It is written in the language of medicine and to the untrained eye, it seems to be talking about a brain disorder, when in fact there is nothing mentioned about the supposed disorder and no medical evidence ever presented that demonstrates its pathological basis, and thus why there is no lab test for it.

And yet the announcement of this study will worry parents of children who have been labeled with this mythical disorder. They will fear when their children start to drive and wonder if driving privileges should be contingent on their children being in psychiatric “treatment” consisting of daily stimulant drug doses. The already bloated departments of motor vehicles across the country might even see this and similar studies as reason to implement new rules and programs about monitoring or denying driver’s licenses to people “with ADHD”.

But if we brush away all the medical-sounding and misleading language, we are left with a trivial study. In short, its results are saying that people who don’t pay attention while driving are at increased risk of having accidents. Aren’t we already able to make that assumption? When we don’t pay attention, we don’t notice things. It doesn’t take a scientific study to tell us this. And it doesn't need the creation of a disorder.

In addition, there are basic statistical issues with this study that further trivialize it. When comparing the driving records of people “with ADHD” and people who have not been given that diagnosis, the study concluded, “…the crash hazard among newly licensed drivers with ADHD was 36% higher.” In the first place, this is inaccurate. The wording makes it sound that people “with ADHD” are more dangerous on the road than people without that diagnosis. But the statistics used in studies like this one are based on group averages, not individuals. In this study, the average number of accidents for the group of ADHD people was claimed to be 36% higher than the average number of accidents in the non-ADHD group. Graphically, this would look something like the following display of two normally distributed (bell curved) groups. The horizontal axis represents the number of accidents and the height of the curve is the number of people with that number of accidents. The dark group would be the people without a diagnosis of ADHD and the lighter color group would be those “with ADHD”.

One can easily see with this graphical representation that even though the average (indicated by the vertical line) number of accidents of the ADHD group is higher than the non-ADHD group, many people in the ADHD group have less accidents than many people in the non-ADHD group. The reverse is also true: many people in the non-ADHD group have more accidents than people in the ADHD group. The reason the researchers say there is a 36% increased crash hazard among ADHD drivers is only because the average number of crashes is higher than the average number of crashes for the non-ADHD group. Still there a many ADHD people with less accidents than people with no diagnosis.

This is because the 36% increased risk of accidents is minimal. As an example, ADHD males in this study had a 13% risk of having an accident within 6 months after getting their driver's license. On the other hand, non-ADHD males only had a 9% risk. Even though this is only a 4% absolute difference in risk, the relative difference is a 44% increased risk when compared to non-ADHD males. Using the relative difference in risk makes it sound more important than it really is.

As an aside, it is interesting to note that the researchers had the diligence to test whether stimulants prescribed to the ADHD people had any effect on accident risk. One might think that taking a daily dose of Ritalin, which is chemically similar to cocaine, could negatively affect driving skill. But, the researchers found that it didn’t. But this begs the question, then, of what value are the stimulants? If those ADHD people who were prescribed stimulants had the same accident risk as those who hadn’t been prescribed stimulants, but who were still diagnosed with ADHD, that suggests the conventional stimulant drug treatment is useless in increasing attention and, in this study, in reducing accident risk. This is not good news for the advocates of drug treatment.

In short, this study is trivial because it is saying that people who don't pay attention while driving are at a higher risk of having accidents. This is a "duh!" conclusion. Nonetheless, the authors mislead away from this simple fact of life and give the impression that a disorder called ADHD causes those accidents. Recommending further study to identify the "specific mechanisms by which ADHD influences crash risk" is absurd. It is absurd because there are no mechanisms of ADHD. It is tantamount to saying we want to find the specific mechanisms of inattention. What would those be? Inattention is inattention and it can be problematic. But even worse, the authors talk about developing "countermeasures" to this inattention. Those so-called countermeasures are very likely going to be just further authoritarian and inhumane attempts at control, not because they would be focused on reducing accidents, but because they would be focused on "treating" a mythical disorder.