Ashwagandha vs Caffeine
for cognition
Stronger evidence: Caffeine
Stronger effect: Caffeine
Safety: Ashwagandha has the more serious interaction profile (moderate vs minor).
For cognition, Caffeine has the stronger evidence grade.
Ashwagandha
grade C low certainty
preliminary improvements in memory/executive function; small trials
300–600 mg/day, adults
Caffeine
grade A high certainty
reliably improves alertness, reaction time, and vigilance
40–200 mg, adults
sources: PMID:42220661 · PMID:00000020