Attention Research Update

January 2005

"Helping parents, professionals and educators stay informed about new research on ADHD"

David Rabiner, Ph.D.  Senior Research Scientist, Duke University



Teens with ADHD, Medication Treatment, and Driving Safety


As a parent of a relatively new teenage driver, I have experienced first hand the anxiety that can be associated with watching your child pull out of the driveway.  For parents whose teen has ADHD this may be especially anxiety provoking because difficulties with attention and impulsivity can compromise the ability to drive conservatively and safely.  In fact, research has demonstrated that adolescents with ADHD are 2 to 4 times more likely to experience motor vehicle accidents, and over three times more likely than other teens to incur associated injuries.

Research has also shown, however, that medication treatment can improve the driving performance of teens with ADHD.  In one study of this issue, the simulated driving performance of adolescent and young adult males with ADHD was significantly worse than matched controls when they had been given placebo before the test. However, 1 to 1.5 hours after taking medication, their driving performance improved to the point that it no longer differed from controls. (The medication tested in this study was immediate release methylphenidate, which is the generic version of Ritalin).

Although this result demonstrates that medication treatment can improve adolescents' driving, short acting medications must generally be administered 3 times per day to achieve full day coverage.  Even when this dosing regimen is followed, however, blood level concentrations wax and wane during the day, which may be associated with fluctuating levels of symptom management. During evening hours, as the final dose of medication is wearing off, there may be a "rebound" of symptoms that could make driving during this time especially problematic.

In recent years, an important advance in medication treatment of ADHD has been the introduction of longer acting preparations (e.g., Concerta, Adderall XR, Ritalin LA).  These medications often provide full day symptom management with a single dose, and because there is also less fluctuation in blood level concentrations, may reduce the ebb and flow of symptoms associated with short acting meds.  This suggests that such medications may be even more effective in promoting safer driving among adolescents with ADHD.  This possibility was examined in a recently published study titled the "Impact of methylphenidate delivery profiles on driving performance of adolescents with ADHD: A pilot study" (Cox et al., (2004). Journal of the American Academy of Child and Adolescent Psychiatry, 43, 269-275). 

Participants were 6 males with ADHD; their mean age was 17 and they averaged 15 months of driving experience.  Their driving performance was tested under 2 medication conditions - 3 daily doses of immediate release methylphenidate and 1 daily dose of Concerta, an extended release version of methylphenidate that provides up to 12 hours of symptom coverage with a single dose.  In both conditions, a careful titration procedure was used to determine the optimum dose for each participant.

Two types of driving data were collected.  First, participants maintained a daily driving diary for 7 days on each type of medication.  Each day, they rated how frequently they engaged in 7 risky driving practices, e.g., tailgating, on a 0 ("not at all") to 3 ("quite a bit") scale.  This diary provided self-report ratings of risky driving in real-world conditions.

To obtain more precise and controlled information about participants' driving while on each medication, a laboratory assessment of driving safety using the Atari Research Driving Simulator was conducted.  This is a realistic, interactive simulator that generates accurate, reliable, sensitive, and valid driving performance data.  The simulator has 3 25-inch computer screens that wrap around the driver, providing a visual experience comparable to actual driving.  The driving experience is realistic, incorporating a typically sized steering wheel, gas and brake pedals, seat, and seat belt.  The simulator also provides "drivers" with visual, auditory, and kinesthetic feedback that is comparable to actual driving conditions.

During the simulated driving test, data is recorded multiple times each second to generate 9 different driving performance variables.  Three of these variables reflect steering control (driving off the road, veering across the midline, erratic steering), 4 reflect braking (inappropriate braking while on open road, missed stop signals, bumps with impact < 5 miles per hour, and collisions with impact > 5 miles per hour), and 2 reflect speed control (exceeding the speed limit, and variability of driving speed).  These variables are combined into a single composite score of impaired driving with higher scores indicating more dangerous driving behavior.

The driving simulator test was completed on 2 separate days, once when participants received their 3 daily doses of methylphenidate (given at 8 AM, 12 PM and 4 PM) and once when they received a single morning dose of Concerta.  On each day, participants completed a 20-minute simulated drive at 2 PM, 5 PM, 8 PM, and 11 PM so that variability in driving performance during the day could be examined.


RESULTS


A comparison of participants driving simulator scores during each medication condition was striking.  At the 2 PM and 5 PM assessments, the impaired driving score was comparable for each medication condition. However, when participants received regular methylphenidate, there was an enormous increase in dangerous driving behavior at the 8 PM assessment, and an indication that their driving continued to worsen between 8 and 11 PM.  In the Concerta condition, in contrast, participants' driving scores showed no such decline and remained steady across all 4 testing times.

In addition to this difference in the composite score, driving performance was better in the Concerta than the regular methylphenidate condition for all 9 variables measured.  These differences were most pronounced for inappropriate braking, percent of missed stop signs, variability in speed, and collisions with impact > 5 mph.

To put these results in perspective, the researchers evaluated participants driving performance at the 8 PM assessment in relation to extensive normative data collected with the driving simulator on over 300 middle-aged and senior drivers.  Participants' driving performance while on Concerta was comparable to a low-risk group of male drivers aged 50-55.  When receiving 3 daily doses of methylphenidate, however, they performed like a high-risk group of males aged 80 and above. 

Results obtained with the simulator were consistent with participants' daily driving records, as they rated themselves as engaging in more risky driving behavior when taking regular methylphenidate then when taking Concerta.


SUMMARY AND IMPLICATIONS


Results from this study clearly indicate that when adolescent drivers with ADHD were treated with Concerta, they demonstrated less variability and performed significantly better throughout the day on objective measures of driving performance than when they were treated with 3 daily doses of immediate release methylphenidate.  Although driving performance was comparable during afternoon and late afternoon assessments, in the evening, when parents are often most concerned about their teens' driving, the differences in driving safety were substantial.  When taking Concerta, teens' driving during evening hours continued to match the performance of low-risk middle-aged males.  When taking methylphenidate, however, their performance declined to a level comparable to males ages 80 and above.

What is particularly striking about these results is that 3 daily doses of methylphenidate and 1 morning dose of Concerta should both provide approximately 12 hours of symptom coverage.  Therefore, how can the dramatic difference in evening driving performance be explained?  The authors suggest 2 possible explanations. First, they speculate that with Concerta, there may be less waxing and waning of medication levels during the day, and that this may result in more stable driving performance. 

They also suggest that the sharp decay in driving performance at 8 PM that was evident with methylphenidate may reflect a rebound phenomenon in which ADHD symptoms get even stronger than usual as the medication wears off.  This type of rebound effect has been reported clinically and is consistent with the data from this study.  There was no evidence of any such rebound, however, for Concerta.

Although ADHD is often regarded as a school-based disorder, with poor academic performance frequently cited as the most serious consequence of undertreatment, the impact ADHD can have on driving performance is also profound.  Results from this study suggest that when the focus of ADHD treatment is solely on minimizing symptoms during the school day, it may have potentially dangerous consequences for after school driving.  Thus, when medication treatment has been determined to be an appropriate treatment for a teenager, consideration should be given to a treatment approach that may reduce the risk of driving accidents during evening hours, as well as during the day.

There are limitations to this study that are important to be aware of.  First, adolescent females were not included, and the extent to which similar results would be found with girls is unknown.  Second, only 6 adolescent males were tested, which is why the authors describe their results as preliminary.  However, it was also the case that every participant drove substantially better during the evening assessments while receiving Concerta, so it is likely that the findings are robust.  As noted above, this study was published in the Journal of the American Academy of Child and Adolescent Psychiatry, which is generally regarded as the premier journal in child psychiatry.  It is certainly unusual that this journal would publish a study that involved only 6 subjects.  I suspect that the reason the editor published the study is because the magnitude of the findings were so large that she felt it was important for the field to know about, even though the sample size was small.

Important - As noted in my introduction to this issue, even though this study indicates that adolescent males drive more safely when receiving Concerta than when receiving immediate release methylphenidate, it cannot be concluded that Concerta is superior to other long acting ADHD medications, e.g., Adderall XR, Ritalin LA, Strattera, as these compounds were not tested.  It is quite possible that these other medications would be just as effective as Concerta in promoting better driving by teens during the evening hours.  Results from this study should also not be used to suggest that all adolescent males with ADHD should receive medication treatment.  The impact of treatment on adolescents' driving is only one of several considerations when deciding on the most appropriate treatment for an individual teen, and not all teens will have a positive response to medication.

Other interventions, particularly well-conducted behavior therapy, have been shown to be effective in managing ADHD symptoms.  I am not aware, however, of studies that have examined whether non-medical interventions also improve the driving safety of teens with ADHD.  Studies of non-medical interventions to improve driving in teens with ADHD would thus be important to pursue, especially since not all teens will be helped by medication, some experience intolerable side effects, and some may be unwilling to take medication regardless of whether it is helpful.  Such work could be quite helpful to parents as they seek the most effective ways to promote safe driving in their teenage children who have ADHD.


Information presented in Attention Research Update is for informational purposes only, and is not a substitute for professional medical advice.  Although newsletter sponsors offer products and services that I believe will be of interest to subscribers, sponsorship of Attention Research Update does not constitute a specific endorsement or guarantee of any company's product or services.