On meds, drivers with ADHD far less likely to suffer car accidents, study finds

STOCKHOLM — It is well-known that sufferers from Attention Deficit Hyperactivity Disorder (ADHD) are more likely to experience motor vehicle accidents while driving. But until recently, science could only hypothesize that ADHD drivers who were properly medicated for their condition would be less likely to suffer such accidents.

The results of a new study conducted by Zheng Chang of the department of medical epidemiology and biostatistics at the Karolinska Institute in Stockholm, Sweden appear to have confirmed that hypothesis – in spades.

Chang and his research team obtained confidential data from health insurers and pharmacies that allowed them to identify whether drivers with ADHD had filled their prescriptions for pharmaceuticals like Ritalin and Adderall in the period prior to their accident – and thus, were likely to have been medicated at the time.

Person driving a car
A new study finds that ADHD sufferers are far less likely to be involved in a motor vehicle accident when they take medication.

What they found was startling: Male ADHD sufferers who had filled their prescriptions were 38% less likely to have had an accident; female patients were 42% less likely.  The results couldn’t have been clearer.

Chang’s team also found that the same pattern held true regardless of age and that it persisted over time: Those on medication were far less likely to be involved in a vehicle accident up to two years later, according to hospital room entry records and health insurance data.

In fact, the study probably underestimated just how much proper ADHD medication can reduce the accident rate.  For one thing, Chang’s team only looked at major vehicle accidents, i.e., those that required hospitalization — not the far more common minor accidents in which drivers simply exchange insurance information and go their separate ways.

Moreover, merely filling a prescription is an imperfect indicator of whether a patient is actually taking his or her medication, especially on the day in question.  A lapse of a single day could leave the sufferer far more vulnerable to the effects of his or her condition.

In short, the actual reduction in the accident rate due to medication could be far higher than the numbers that Chang’s team reported.

Still, the study marks a significant breakthrough by establishing a solid baseline for further research.  Chang’s team examined a pool of nearly 2.3 million ADHD sufferers.  Their study was the first to link an ADHD sufferer’s prescription use to his or her motor vehicle accident record.

“[It] is the first time that we could quantify the effect size [of medication on vehicle accidents] in a large population sample of ADHD patients in the U.S.” Chang noted in an interview with WebMD.

The issue of ADHD and driving has gained increasing attention in recent years, thanks to a sharp increase in motor vehicle accidents and a rise in the prevalence rate for ADHD, especially among youth.  Car accidents are the leading source of fatality among young adults, but experts say that many ADHD sufferers – due precisely to the symptoms of their disease — may not realize that they are under-medicated when they get behind the wheel.

Once on the road, research shows that those with the disorder are more likely to run stop signs, speed, change lanes without signaling, and engage in other forms of reckless or “distracted” driving, leading to a 50% higher rate of serious car crashes than among drivers at large.

Some health specialists believe that family-based prevention programs might help educate vulnerable ADHD youth about the need to maintain a strict medication regimen while transitioning to independent driving.  However, such programs, which are still being piloted, thus far appear to have produced mixed results.  Chang’s study suggests that all ADHD sufferers — not just youth — may need better education about the dangers of driving without proper medication.

Chang’s findings were first reported in the web edition of the Journal of the American Medical Association (JAMA).