Undiagnosed ADHD May Be Tied to Car Crash Injuries in Adults

Undetected attention deficit-hyperactivity disorder (ADHD) was not uncommon among adults hospitalized after traffic accidents, according to a cross-sectional study from the Dominican Republic.

Among 95 adults admitted for traffic-related injuries without a prior diagnosis, more than a third (34.7%) screened positive on the Adult ADHD Self-Report Scale, reported Amanda Abreu, MD, of the Universidad Iberoamericana in Santo Domingo, Dominican Republic.

High-risk driving behaviors — including violations, mistakes, and slips — were more common among adults who screened positive (66.6% vs 30.6%, P=0.0016), she reported at the American Psychiatric Association annual meeting.

“We’re not saying that ADHD alone caused the accidents, nor are they unsafe drivers, but these findings suggest that this is a really vulnerable population we should look into, and we should help protect,” Abreu said.

“Road safety is not only about cars, and it’s not only about roads — it’s also about people. It’s also about health. It’s also about behavior,” she continued. “Driving requires attention, executive functioning, and impulse control. These happen to be all impaired in ADHD.”

Possible links between ADHD and driving behavior have been widely studied. A 2023 U.S. cohort study reported a 102% increased risk in traffic ticket events and a 74% increased risk in vehicle crashes among older adult drivers with ADHD compared with those without the disorder.

Additionally, a recent target trial emulation found significantly lower rates of transport accidents among individuals with ADHD who started drug treatment within 3 months of their diagnosis. A small study also found that a simulated driving program benefited teens with ADHD, reducing inattention and crash risks compared with conventional driver’s training.

This observational, cross-sectional analysis focused on 95 adults without a prior ADHD diagnosis. All were hospitalized at a center in Santo Domingo and were screened using part A of the 18-item Adult ADHD Self-Report Scale. Driving behavior and risk were evaluated with the Driving Behavior Questionnaire, which classified behaviors into violations, unintentional violations, mistakes, slips, and overall risk categories and graded them on a 3-point scale.

Adults who screened positive for ADHD tended to be younger (mean age 27.3 vs 35.7, P<0.01), highlighting a "vulnerable subgroup" for targeted intervention, said Abreu. Also, ADHD-positive adults were less likely to have a valid driver's license.

Nearly half (48.5%) of traffic events among ADHD-positive adults were caused by intentional violations, while this only accounted for 11.3% of events in ADHD-negative individuals. Conversely, the vast majority of traffic accidents in ADHD-negative adults were due to mistakes and unintentional violations.

The Driving Behavior Questionnaire was originally developed in the U.K., Abreu pointed out, which means it may not account for cultural differences in driving habits.

“Driving behavior in the U.K. is really different from the Dominican Republic,” she said. “Most of the things that may be categorized as intentional violations or high overall risk might reflect a real safety issue in the country.” For example, she explained that in the Dominican Republic, it is common for women to run red lights when driving in unsafe areas at night. According to the questionnaire, this behavior would be labeled as impulsivity.

“There’s bias right there,” she noted. “That’s why we encourage culturally sensitive tools so we can apply them to different contexts.”

Another limitation Abreu highlighted was that only the ADHD screening tool was used, and individuals did not undergo a formal clinical diagnostic evaluation.