It’s called the ‘paradoxical calming effect’. Here is a nature article on it [https://www.nature.com/articles/s41598-022-07029-2 https://www.nature.com/articles

It’s called the ‘paradoxical calming effect’. Here is a nature article on it [https://www.nature.com/articles/s41598-022-07029-2 https://www.nature.com/articles/s41598-022-07029-2]. Here is more detailed data [https://www.researchgate.net/publication/45708101_Role_of_Aberrant_Striatal_Dopamine_D-1_ReceptorcAMPProtein_Kinase_ADARPP32_Signaling_in_the_Paradoxical_Calming_Effect_of_Amphetamine https://www.researchgate.net/publication/45708101_Role_of_Ab...]. It doesn’t happen to everyone with ADHD, but the majority. The effect itself was prominent/notable as early as WW1, as the drugs were widely used by all parties to help fight fatigue and drowsiness. However, a small percentage of the population would end up with the opposite effect - ending up tired, even sleepy, and often calmer instead of more alert. It took awhile however, before wider implications of sub-population differences in drug effects like this were studied or applied.