Unmedicated ADHD Patients: Accidents Waiting to Happen?

Fran Lowry

January 30, 2014

Could patients diagnosed with attention-deficit/hyperactivity disorder (ADHD) who are prescribed ADHD medications but who drive without them be a danger to themselves and others when they drive?

New research from the Karolinska Institutet in Stockholm, Sweden, suggests that this may be the case.

According to the results of a large registry study, ADHD is associated with an increased risk for serious transport accidents, a risk that might be reduced by ADHD medication, at least among men.

"Studies have shown that ADHD is associated with serious transport accidents, but it is unclear whether ADHD medication reduces this risk," senior author Henrik Larsson, PhD, told Medscape Medical News. "Our study demonstrates that the risk of transport accidents with adult men with ADHD decreases markedly if their condition is treated with ADHD medication."

The study was published online January 29 in JAMA Psychiatry.

Medication Reduced Risk

Several other studies have shown that adults with ADHD who drive without being on medication have less skill at the wheel compared with adults who do not have ADHD.

In a recent study presented at the 26th European College of Neuropsychopharmacology (ECNP) Congress and reported by Medscape Medical News, Esther Sobanski, MD, from the University of Heidelberg, in Mannheim, Germany, reported that the selective norepinephrine reuptake inhibitor atomoxetine, approved for treating ADHD, might improve adult driving skills.

Another study found that teenagers with ADHD became better drivers when they were trained on a driving simulator.

And in an earlier study, also reported in Medscape Medical News, researchers from the University of Virginia in Charlottesville showed that older adults with ADHD could be more prone to automobile accidents than their peers without the disorder.

Dr. Henrik Larsson

In the current study, the investigators studied 17,408 individuals with ADHD during a period of 4 years, from 2006 to 2009, using various Swedish national registers.

They then analyzed the risk for transport accidents for those diagnosed with ADHD and how use of ADHD medication influenced this risk.

They found that, compared with individuals without ADHD, individuals who had ADHD had an increased risk for serious transport accidents. For men, the adjusted hazard ratio [AHR] was 1.47; (95% confidence interval [CI], 1.32 - 1.63), and for women, the AHR was 1.45 (95% CI, 1.24 - 1.71).

However, use of ADHD medication attenuated this risk.

Public Policy Implications?

In men, medication was associated with a 58% risk reduction (hazard ratio [HR], 0.42; 95% CI, 0.23 - 0.75).

In women, however, there was no statistically significant association between medication use and reduction in the risk for a transport accident.

From their analyses, the researchers concluded that 41% to 49% of the accidents in male patients with ADHD could have been avoided if they had been receiving treatment during the follow-up period of the study.

"These results may be explained by ADHD medication having an effect on the core symptoms of ADHD, such as impulsiveness and distractibility, which in turn reduces the risk of getting trouble on the road," Dr. Larsson said.

"We could not establish a similar reduction in women's accident risk, and we need further data to be able to comment about the effect on women with statistical certainty," he added.

Dr. Larsson noted that the link between ADHD and serious traffic accidents does not, by itself, justify withholding a driver's licence. Still, he added, the findings "do suggest that a large number of injuries and deaths due to traffic accidents associated with ADHD happened when patients were off their medications.

"Clinicians should consider informing their patients about the increased risk for transport accidents and the possible benefits of ADHD medication. This would not only provide opportunities to reduce morbidity and mortality for patients with ADHD but also contribute to the public's safety," he said.

Treatment Is Beneficial

Commenting on the findings for Medscape Medical News, Lenard Adler, MD, professor in the Departments of Psychiatry and Child and Adolescent Psychiatry at New York University Langone Medical Center, in New York City, called it "an important study because it follows up in a large, community-based registry findings that we have shown from small treatment studies."

Dr. Lenard Adler

Simulator studies have shown that adults with ADHD who are untreated have impairment in driving, and some of that impairment improves when they are treated, he said. "This study takes it out to the real world and looks at accidents, and then shows the percent of accidents that may have been reduced by treatment."

Dr. Adler, who was not involved in this study, noted that prior research has shown that not all drivers with ADHD have impaired driving.

"The ADHD drivers fall into 2 groups. About half of them, from research done at Massachusetts General, are impaired, and about half actually drive okay, but in the group that's impaired, when they are put on a driving simulator, studies have shown that they have more speeding, false brakes, erratic driving," said Dr. Adler.

"They tend to accelerate into critical incidents on the simulator. For example, if you are driving along and you see a tree fall on the road and accelerate into that rather than brake, it obviously has serious consequences. If you give people with ADHD treatment, they drive better and have less of these errors on a driving simulator," he added.

The study by Dr. Larsson and colleagues highlights the importance of recognizing ADHD in adults, Dr. Adler said.

"If you don't know you have it, you can't treat it. If individuals have poor driving records, this may help clinicians identify some who have ADHD. This study clearly highlights the need and benefits of treatment and the importance of adhering to ADHD treatment," he said.

The study was supported by the Swedish Research Council, the Swedish Council for Working Life and Social Research, and the National Institute of Child Health and Human Development. Dr. Larsson reports no relevant financial relationships. Dr. Adler reports financial relationships with Eli Lilly, Shire Pharmaceuticals, Alcobra, and Theravance.

JAMA Psychiatry. Published online January 29, 2014. Abstract


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