Neurocognitive Effects of Extended-Release Methylphenidate in Healthy Adults

Methylphenidate (MPH) is a central nervous system stimulant widely prescribed for the treatment of attention deficit hyperactivity disorder (ADHD). In addition to its clinical use, there has been increasing interest in the use of MPH by healthy individuals for potential cognitive enhancement, academic performance, and physical performance. Despite this growing use, there is limited high-quality evidence on its effects across multiple physiological and functional domains in healthy adults. This study was designed to address these gaps.

This investigation used a randomized, double-blind, placebo-controlled crossover design to evaluate the effects of short-term MPH administration in healthy, drug-naïve adults. A crossover design was selected to allow each participant to serve as their own control, thereby reducing variability and improving the precision of comparisons between treatment conditions. Participants were randomly assigned to receive either extended-release MPH (20 mg daily) or a placebo for 14 days, followed by a washout period and subsequent crossover to the alternate treatment.

The study was conducted in a controlled laboratory setting to ensure consistency in testing conditions and measurement accuracy. Participants underwent a comprehensive assessment battery at baseline and repeated assessments after each treatment phase. These evaluations were selected to provide a multidimensional understanding of MPH's effects across several key domains:

Physiological and cardiovascular function: Resting heart rate and blood pressure were measured to assess potential stimulant-related cardiovascular effects. In addition, cardiopulmonary exercise testing (CPET) was used to evaluate exercise capacity, aerobic fitness (including maximum oxygen consumption, VO₂ peak), ventilatory efficiency, and overall cardiopulmonary performance.

Neurocognitive function: Cognitive performance was assessed using a validated computerized neurocognitive test battery (CNS Vital Signs®). This evaluated domains such as attention, memory, processing speed, executive function, and reaction time. These measures were included because MPH is known to influence dopaminergic and noradrenergic pathways involved in cognitive processing.

Postural balance: Objective balance testing was conducted using the Biodex® Balance System, which evaluates stability under different sensory conditions. This allowed assessment of visual, vestibular, and somatosensory contributions to balance control.

Muscle strength: Handgrip strength, a reliable indicator of overall muscular strength and physical performance, was measured using a calibrated dynamometer.

Cardiac electrical activity: Electrocardiography (ECG) was recorded at rest and during exercise to monitor cardiac rhythm and electrical conduction, ensuring detection of any potential stimulant-related cardiac effects.

Participants were instructed to maintain their usual diet and physical activity throughout the study to minimize confounding factors. All assessments were performed at similar times of day across testing sessions to reduce the effects of diurnal variation.

The study also incorporated rigorous safety and screening procedures. Participants underwent pre-participation health screening, including standardized questionnaires and cardiovascular risk assessment, to ensure suitability for exercise testing and stimulant exposure. Continuous monitoring during exercise testing ensured participant safety.

This study specifically targeted healthy adults without ADHD to isolate the effects of MPH independent of its therapeutic role. By integrating physiological, cognitive, neuromuscular, and cardiovascular measures within a single study design, the research provides a comprehensive evaluation of MPH's potential for performance enhancement or health risk in this population.

Inclusion criteria

• Healthy adults without a diagnosis of ADHD
• Age 18 to 50 years
• Willing to participate after being informed about the study
• Willing to receive both methylphenidate and placebo during the study period
• Willing to undergo non-invasive physiological, cognitive, cardiovascular, balance, and physical performance assessments
• Able to comply with all study procedures and visits

Exclusion criteria

• Current use of any medication that may affect cognitive performance, physical performance, electrocardiogram (ECG) findings, cardiovascular function, or balance
• Any medical, neurological, musculoskeletal, psychiatric, or other condition that may interfere with the safe or successful completion of study assessments and physical performance testing
• Any contraindication to methylphenidate administration