Oh. Easy.
Biphasic dose response.
https://www.sciencedirect.com/science/article/abs/pii/S0269749113004235
Also known as hormesis.
https://en.m.wikipedia.org/wiki/Hormesis
Small/normal doses of cannabis can perk you up. Large ones sedate. Reasonable doses of alcohol give party energy. Larger ones make you go to bed.
Same with caffeine.
And everything, really.