How Caffeine Affects Reaction Time

A 2025 systematic review and meta-analysis included 31 randomized, double-blind, placebo-controlled trials with 1,455 healthy adults. It found significant improvements in both reaction time and accuracy after acute caffeine intake. The reported standardized effect on reaction time was modest rather than dramatic.

A separate systematic review in sports found that low-to-moderate caffeine doses may improve attention, speed and some reaction measures during exercise, although results depended on protocol. In elite esports players, a crossover trial found faster performance on selected visual-search and Stroop measures after caffeine, but not every task improved.

Caffeine can partly counter fatigue-related slowing, but it can also reduce sleep quality or duration when timing and dose interfere with sleep. That creates an obvious loop: a stimulant may improve today's alertness while making tomorrow's baseline worse if it disrupts recovery.

For a long-term reaction-time plan, prioritize sleep and task-specific practice before treating caffeine as a training method.

1. Use the same reaction test, device and input method.
2. Take several trials and record the median or average.
3. Compare multiple days rather than one caffeinated session.
4. Record sleep and time of day so you do not confuse caffeine with alertness differences.

This is an educational performance guide, not medical advice or a recommendation to use caffeine, medication or supplements.

• 2025 meta-analysis of caffeine and attention
• Caffeine and cognitive functions in sports systematic review
• Caffeine crossover trial in elite esports players
• Caffeine, vigilance and fatigued shift-worker meta-analysis