Acute Caffeine Intake Does Not Modulate Active or Reactive Inhibition in Non‐Clinical Young Adults, and ADHD Symptoms Do Not Moderate Its Effects

Summary

This preregistered, double-blind crossover trial examined whether 250 mg of acute caffeine improves inhibitory control (active and reactive) in 36 non-clinical young adults, and whether ADHD symptom severity moderates such effects. Contrary to presumed cognitive benefits of caffeine, the intervention produced no detectable improvements in either form of inhibition; ADHD symptoms similarly did not moderate any effects, though symptoms themselves predicted flanker accuracy. Bayesian analysis supported genuine null effects rather than non-detection, challenging the notion of acute cognitive benefit from caffeine in this population.

Regional applicability

The study was conducted in a nonclinical sample of young adults; geography is not specified in the abstract. The findings have potential relevance to UK dietary advice on caffeine and cognition, though the sample is not UK-specific and applicability depends on population generalisation. The null result contradicts common consumer assumptions about caffeine's cognitive benefits and may inform public health messaging across populations.

Key measures

Commission errors, response criterion, Go reaction time, reaction time variability, flanker reaction time, flanker accuracy; Adult ADHD Self-Report Scale; Bayes factors for null hypothesis quantification

Outcomes reported

The study measured whether 250 mg acute caffeine intake improved active inhibition (Go/No-Go task) and reactive inhibition (flanker task) in non-clinical young adults, and whether ADHD symptom severity moderated these effects. No significant effects of caffeine on any inhibitory control measure were detected, and ADHD symptoms did not moderate caffeine's influence on performance.

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