In a 6-day trial on 26 people, guarana improved secondary memory performance and increased alertness and mood. These changes could not be attributed to caffeine alone.

In another trial on 28 healthy volunteers, guarana improved performance in attention (although it reduced accuracy), sentence verification, and serial subtraction tasks. Its combination with ginseng also increased the speed of attention and memory tasks.

In 3 trials of 169 people, those who consumed multivitamins with guarana had an increased benefit of mood and cognitive performance and reduced mental fatigue compared to those who consumed the vitamins alone. Another multivitamin supplement with guarana improved decision making in a trial on 56 people.

Consuming a similar multivitamin and multimineral complex with guarana before physical exercise reduced fatigue perception and improved memory after the exercise in a clinical trial on 40 active men. Similarly, a mouth rinsing with guarana, caffeine, and carbohydrates reduced fatigue perception and improved cognitive control and physical exercise performance in a clinical trial on 24 people.

Guarana’s effect on mental health and performance may be attributable to a relatively high content of saponins and tannins that may work along with caffeine.

All in all, several studies suggest that guarana may improve cognitive performance. However, most of them were either too small or used guarana in combination with multivitamin and multimineral complexes, making guarana’s contribution difficult to estimate. Larger, more robust trials testing guarana alone are needed to confirm its effects on cognitive function.