Does Stimulant Medication Improve the Driving Performance of Young Adults with ADHD?

In a prior issue of Attention Research Update, I reviewed a study concerning the association between ADHD symptoms at age 13 and the development of driving difficulties during late adolescence/early adulthood.  The results from this study longitudinal indicated that those with high levels of ADHD symptoms were:

·        about 3 times more likely to  be involved in an accident than those  with low levels of symptoms;

·        about 2.5 times more likely to report having driven while seriously intoxicated;

·        about 3 times more likely to have been involved in street racing; and,

·        more likely to have an overall traffic violation score more than twice as high.

 Although these differences were not as pronounced after controlling for other relevant factors (e.g. conduct problems, IQ, family environment factors, driving experience), ADHD symptoms continued to predict the development of driving difficulties.  Most importantly, they predict the risk of an auto accident involving injury.  Results from this study were consistent with several recent reports in which a significant association between ADHD and problematic driving records has been found.

These results provide an understandable basis for why parents of ADHD adolescents may be particularly concerned as their child begins his or her driving career.  It is somewhat surprising that, given the large number of studies in which the effects of stimulant medication have been examined, no studies have examined whether stimulant medication improves the driving performance of individuals with ADHD.  This is an important issue to address, as this evidence may have important implications for recommendations about medication usage.  For example, if medication was found to improve the driving performance of individuals with ADHD, parents and physicians might be more insistent that adolescents receive medication during evenings and weekends.  These are times when medication typically may not be administered and the bulk of an adolescent’s driving is likely to occur.

A study published last year in the Journal of Nervous and Mental Diseases (Cox, D., et al., (2000). Effect of stimulant medication on driving performance of young adults with ADHD: A preliminary double-blind placebo controlled trial (v. 188, 230-234) represents the first effort to document the effects of medication treatment on the driving performance of ADHD individuals.  In this study, 7 young adult males with ADHD and 6 matched comparison subjects (average age was about 22 years) completed two 30-minute driving tests on a sophisticated research-driving simulator.  (The validity of this simulated driving task as an indicator of real-world driving performance has been demonstrated in several prior studies.)  Before one of the tests, participants were given a 10 mg dose of Ritalin.  Before the other test, they were given a placebo (i.e. a vitamin C tablet). The order of medication vs. placebo administration was counter-balanced across all participants.

 The driving scenario used in this investigation was specifically chosen to simulate routine, fairly monotonous driving. These are the types of driving conditions in which individuals with ADHD are more likely to demonstrate poorer performance.  After each 30-minute session, participants were asked to rate their performance on a 1to 5 scale, with 1 being poor and 5 being excellent.  Actual performance data related to steering, braking, and crash variables was also available from the computer-based simulation. The sum of these variables was used to create an impaired driving score for each participant.

Results

The design of this study enabled the researchers to examine 3 interrelated questions:

 1.   Do young adult males with ADHD exhibit poorer driving performance as measured on a computerized driving simulator when compared to matched controls?

2.   Does the driving performance of young adult males with ADHD improve with the use of Ritalin?

3.   Are individuals with ADHD aware of their relative driving performance? 

As expected, in the placebo condition, ADHD participants had significantly higher impaired driving scores than control subjects.  The fact that this difference was statistically significant, given the small number of participants, is striking (i.e. with small samples, it is more difficult to obtain statistically significant results). The results clearly display the magnitude of the difference in driving scores between the 2 groups.  In addition, the results of these simulated driving tests were consistent with the actual driving history of the 2 groups: the ADHD participants had, on average, more than 3 times as many accidents than the comparison subjects.

Despite doing significantly worse in the placebo condition, the driving performance of the ADHD participants was no different than that of controls after taking Ritalin. In fact, every single participant with ADHD obtained a lower impaired driving score on medication than he had on placebo. For the comparison subjects, such improvement was evident in only a single individual.

The participants’ ratings of their own driving performance parallel the results obtained from the actual driving data.  For ratings obtained in the placebo condition, ADHD participants rated their driving performance significantly lower than comparison subjects.  Ratings obtained for the medication condition did not differ between the groups.

Summary and Implications

This is the first study to provide evidence that stimulant medication - in this case, Ritalin—can yield substantial improvements in the driving performance of individuals with ADHD.  As noted above, all 7 participants with ADHD provided evidence of safer driving after taking Ritalin.  Despite the small sample size and the necessary cautions about generalizing these findings to the larger population of individuals with ADHD (i.e. we do not know whether similar results have been obtained with adolescents, older adults, and females), these are important results for parents and clinicians to consider.   Clearly, it will be important to replicate this study with a larger and more diverse sample.  

In the meantime, this data still has important clinical implications for parents and practitioners to consider.  It is relatively common practice for individuals with ADHD to follow a dosing regimen in which medication is restricted to those times of the day and/or week when it is felt to be most necessary.  For adolescents, this would typically be the school day dose, and perhaps a late afternoon dose to assist with homework.   For adults, this would generally be for hours corresponding to their work schedule.  During evenings and weekends, however, when adolescents and adults may do the bulk of their driving, this regimen is unlikely to provide any benefit to their driving safety.

Teen-age drivers with ADHD may be especially unlikely to be on medication at those times when the risk of a serious auto accident (i.e. late evenings) is greatest.

It is clear that many adolescents are resistant to taking medication.  With that in mind it is important to note that these results should definitely NOT be interpreted as a requirement for ADHD adolescents to take medication before driving.   In the first place, it is important that this study be replicated with adolescents to be certain that the same findings apply.   Even if this is found to be the case, there is always the need to consider the specifics of each individual’s circumstances.  With these important caveats in mind, however, the results from this investigation suggest that there may be important benefits for ADHD individuals who take medication while driving. This is an issue that parents and health professionals may wish to consider.

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