Researchers estimate that 1 in 5 of vehicle accidents involving people with ADHD could have been avoided if they had been on the proper medication.

Medication for attention-deficit/hyperactivity disorder (ADHD) may help to lower the risk of motor vehicle crashes among patients with ADHD, a study published May 10 in JAMA Psychiatry suggests.

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In a national sample of 2.3 million patients with ADHD in the United States, those who took ADHD medication were significantly less likely to be involved in crashes.

Motor vehicle crashes are a major public health problem, and research has shown that individuals with ADHD are more likely than others to experience these accidents. The purpose of the study was to explore the association between ADHD medication use and the risk of motor vehicle crashes in a large cohort of patients with the disorder.

Zheng Chang, Ph.D., and colleagues in the Department of Medical Epidemiology and Biostatistics at Karolinska Institutet in Stockholm, Sweden, used data from the Truven Health Analytics MarketScan Commercial Claims and Encounters database to identify people aged 18 and older who had an ADHD diagnosis or had received ADHD medication between January 2005 and the end of December 2014. Patients were tracked from first inpatient or outpatient diagnosis or filled prescription until first disenrollment (zero days of medical or drug coverage in a month) or December 31, 2014, whichever came first. The number of emergency department visits for motor vehicle crashes for these patients was compared with that of non-ADHD controls.

The study cohort consisted of 2,319,450 patients diagnosed with ADHD; the mean age was 32.5 years, and 51.7 percent were female.

During follow-up, 1,946,198 patients (83.9 percent) received at least one prescription for an ADHD medication. A total of 11,224 patients (0.5 percent) had at least one emergency department visit for a motor vehicle crash. Patients with ADHD had a significantly higher risk of a motor vehicle crash than matched controls (odds ratio [OR]=1.49 for men and OR=1.44 for women). Untreated patients with ADHD had the highest risk of a motor vehicle crash compared with medicated patients with ADHD and controls.

Chang and colleagues also compared the risk of motor vehicle crashes in individual patients during months when they were medicated and not medicated. Male patients had a 38 percent lower risk of crashes when taking ADHD mediation compared with months not receiving the medication, while female patients had a 42 percent lower risk. Similar decreases existed in all age groups.

ADHD medication use was associated with a 34 percent lower risk of accidents two years later in male patients with ADHD and a 27 percent lower risk in female patients with ADHD.

The findings suggested that up to 22.1 percent of the crashes involving ADHD patients could have been prevented if they had been taking medication.

“These findings call attention to a prevalent and preventable cause of mortality and morbidity among patients with ADHD,” wrote the researchers. “If replicated, our results should be considered along with other potential benefits and harms associated with ADHD medication use.”

The study is the first to “demonstrate a long-term association between receiving ADHD medication and decreased motor vehicle crashes,” the authors wrote. “If this result indeed reflects a protective effect, it is possible that sustained ADHD medication use might lead to lower risk of comorbid problems … or contribute to long-term improvements in life functioning.”

“Clinicians should not presume that all ADHD medications at any dosage will be effective for every patient,” Vishal Madaan, M.D., and Daniel J. Cox, Ph.D., wrote in an accompanying commentary. They are in the Department of Psychiatry and Neurobehavioral Sciences in the University of Virginia Health System. “Health care professionals should ensure that both the medication and dosage are optimal for a particular patient-driver, that the medication coverage is adequate for the particular patient’s driving routine, and that the medication prescribed is not responsible for worse driving as its effects wear off (rebound effect).”

In addition to asking patients about school and work performance, clinicians should ask about symptoms “suggestive of distracted driving” such as repeated speeding tickets, missing traffic signs, swerving and switching lanes haphazardly, road rage, and consistently fiddling with the radio, Madaan told Psychiatric News.

He also advised that if a patient is taking an ADHD medication that works well, clinicians should ensure that it lasts long enough to cover times when the patient may be driving. ■