Ritalin on the road: ADHD drug methylphenidate improves driving performance

A recent study conducted in Australia found that a 10 mg dose of methylphenidate improved participants’ driving performance in a simulated driving task. The medication reduced lane weaving and speed variation, while eye movements remained almost unaffected. The research was published in the Journal of Psychopharmacology.

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental condition characterized by inattention, hyperactivity, and impulsivity, which adversely impacts daily functioning. It is most often diagnosed at the start of school, as these symptoms are considered disruptive in the classroom context. ADHD symptoms can persist into adulthood, leading to detrimental consequences in various areas of life.

In adulthood, ADHD symptoms can significantly impair driving performance. Individuals with ADHD may struggle to sustain attention, manage distractions, and inhibit inappropriate responses. This can lead to difficulties such as missing road signs, reacting slowly to hazards, or engaging in impulsive driving behaviors like speeding or risky overtaking.

One medication widely used to treat ADHD is methylphenidate. It works by increasing levels of the neurotransmitters dopamine and norepinephrine in the brain, thereby enhancing focus, attention, and impulse control. While generally effective, methylphenidate can cause side effects such as insomnia, decreased appetite, and increased heart rate.

Study author Blair Aitken and his colleagues sought to investigate the acute effects of a 10 mg dose of methylphenidate on driving performance while simultaneously monitoring eye movements in a simulated driving environment. A dose of 10 mg is generally considered low and corresponds to the initial dosage typically prescribed at the beginning of therapy. This low dose was deemed appropriate for studying the effects on individuals with minimal prior exposure to the drug.

The study involved 25 healthy adults, 16 of whom were male. Participants ranged in age from 23 to 47 years. Eligibility criteria included holding a valid driver’s license, having at least 4,000 kilometers of driving experience per year, and being in good general health.

Each participant completed two experimental sessions, scheduled at least a week apart to minimize any residual effects of the drug. In one session, participants received a 10 mg dose of methylphenidate (Ritalin®). In the other session, they were given an identical-looking capsule containing no active ingredients (placebo). Participants were unaware of whether they had received methylphenidate or the placebo.

Eighty-five minutes after taking the drug, participants were required to drive for 40 minutes in a simulator. Their task was to maintain a steady position in the left lane at a constant speed of 100 km/h, occasionally performing overtaking maneuvers due to traffic conditions. The driving scenario replicated a 105-km four-lane highway with standard Australian road markings and signage. A camera mounted on the simulator’s dashboard tracked participants’ eye movements.

Each session lasted approximately three hours. Participants were compensated with $50 and a transportation voucher. Prior to testing, they were instructed to fast for two hours, avoid caffeine for 12 hours, and abstain from alcohol and nicotine for 24 hours to minimize confounding effects.

The results showed that participants under the influence of methylphenidate exhibited less lane weaving and maintained a more stable speed. Reduced lane weaving was noticeable after 30 minutes of simulation, while more stable speed control emerged at the 40-minute mark. Additionally, participants moved the steering wheel less between 10 and 20 minutes into the session but showed increased steering activity between 30 and 40 minutes when on methylphenidate.

Participants did not report perceiving any subjective differences between the sessions with methylphenidate and placebo. However, after the driving task, participants who had taken the placebo reported feeling slightly sleepier than those who had taken methylphenidate. Differences in eye movements between the two conditions were minimal.

“This study demonstrated that an acute 10mg dose of methylphenidate demonstrated protective effects against performance degradation commonly observed during prolonged, monotonous driving, evidenced by improvements in vehicle control and speed maintenance relative to placebo. The limited changes in broader ocular metrics suggest that while methylphenidate enhances specific aspects of cognitive function, it does not universally improve visual scanning efficiency,” the study authors concluded.

The study sheds light on the effects of methylphenidate on driving performance. However, it is important to note that the driving simulation used was relatively simple, featuring a highway with relatively few vehicles. This simplicity may explain the absence of significant effects on eye movements. Results may differ in more complex driving situations.

The paper, “Driving performance and ocular activity following acute administration of 10mg methylphenidate: A randomised, double-blind, placebo-controlled study,” was authored by Blair Aitken, Luke A Downey, Serah Rose, Thomas R Arkell, Brook Shiferaw, and Amie C Hayley.