A double-blind, placebo-controlled, multi-dose evaluation of the acute behavioural effects of guarana in humans

The present study aimed to systematically assess acute, dose-related behavioural effects of an extract of guarana plant for the first time in humans. This double-blind, counterbalanced, placebo-controlled study (n=26) assessed the acute mood and cognitive effects throughout the day of four different doses (37.5 mg, 75 mg, 150 mg and 300 mg) of a standardised guarana extract (PC-102). Assessment included the Cognitive Drug Research computerized test battery and Bond-Lader mood scales. Guarana improved secondary memory performance and increased alert and content mood ratings. The two lower doses produced more positive cognitive effects than the higher doses. This research supports previous findings of cognitive improvements following 75 mg guarana and provides the first exploration of different dose effects of guarana in humans. The findings suggest that the effects cannot be attributed to caffeine alone.