Well, supposedly caffeine is supposed to help calm people with ADHD, but too much causes tremors and stuff, as does too much stimulant medication, so the combo of meds and caffeine may have been your issue, rather than the coffee by itself. And sleep deprivation probably didn’t help matters. I have only felt that twitch when I have had a couple of strong coffees on night shift. I tend not to drink coffee because I worry it will disrupt my already poor sleep. I went and did a bit of research after your post, and it prompted a few thoughts….
I think it’s worth trialling regular daytime coffee on my days off to see what effect it has on my suspected ADHD symptoms (as opposed to when I am on night shift). It is supposed to help ADHD symptoms according to what I read, but I have always had the suspicion that I have restless legs syndrome, in which case coffee at night would definitely cause irritability/twitchiness, counteracting the calming effect it should have for those with ADHD. I once tried someone else’s meds for RLS (naughty, I know, but I was despairing at the time) and they certainly helped me keep still overnight. If coffee in the day helps keep my mind from racing every-which-way and keeps me focussed, then I think I have to face the fact that I probably have both ADHD and RLS 
It’s hard though, as there is always the placebo effect to consider. The slug of coffee I had an hour ago (1 1/2 tsp coffee mixed with a bit of warm water as a “shot”) seems to have helped my focus and made me relax, without making me jumpy/twitchy. Hmmmm. Something to think about. Will see how much housework I can focus on this week and that should be a giveaway lol 😉 It’s always the first thing to slide when I get overwhelmed/stressed.
Interestingly, I also made my son (ADHD confirmed) have a drink of strong iced coffee, as he has a book report to finish and he had been yelling at me over it. He is now at the computer typing it up, and hasn’t yelled at me since. I think a coffee before school might be the way to go until his doctor’s appointment to discuss medication. But the caffeine wearing off part later in the day might be unpleasant for all concerned!!!
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