system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does caffeine have a calming effect on some individuals with ADHD, as opposed to making their traits increase?
gpt
Clinical psychologist here.

It's not that caffeine produces a calming effect, it's that caffeine improves function of the frontal lobe which is responsible for executive function, which oversees other operations in the brain.

ELI5:

Think of an ADHD brain as one of those old-school factories where the foreman's office was above the line, except the foreman is sleeping and so normal operations slip. Caffeine (and other stimulants) wake him up so he can do his job overseeing the work.

Non-ELI5:

There are two predominant models of ADHD. Barkley's inhibition model and Rapport's working memory model. Barkley's model suggests its difficult not to blurt out the answer.  Rapport's model posits (if we use a metaphor) that if a behavior was a 'photograph' , that those with ADHD struggle to hold that 'photograph' in mind as a guide for their behavior.