I developed this unique tea leaf / tree bark mix over 20 years ago, and I could swear it changed my life. I studied for 14 hours per day sometimes and absorbed all my training within a few years. Then the effect was gone.

Looking at it objectively, maybe the trick was that it had just the right amount of caffeine, but unlike pure black tea, not too much at once and with a lot of water. Possibly also compensating a micro nutrient deficit. Could also be complex indirect effects, e. g.: ADHD related to gut biome, additional problems due to bad bacteria / yeast overrepresented, medicinal plants in the mix fighting that, to a mild degree.

Treating digestion problems with medicinal tea in combination with caffeine and love for black tea started the whole idea, IIRC, so it's not entirely impossible.