If something increases heart rate, sometimes the body will vasodilate to compensate.

[delayed]

Stimulants can act tranquilizing for some ADHD people.

And for some people, drugs like Valium act as stimulants. My dad had that problem. He also had two different medical conditions that were rare enough that they each got separately dramatized on "House, MD". When my mom passed away, I got a copy of his medical file. There were multiple binders, filling multiple shelves.

Just before our wedding, my dad had an crisis, and had to go to the hospital with an infection. He went to Johns Hopkins. They put him in the research wing. The doctors couldn't figure out what the heck to do with him because he was reacting so weird to so many medications. They ended up having to pump him full of vancomycin in hopes that he would last long enough on the three hour flight to get back home where his regular doctor could see him.

People are individuals, and their bodies can react in weird and unexpected ways.

Unmedicated ADHD causes a great deal of anxiety. Making your brain operate as intended reduces anxiety, which lowers your vitals.

That said, whether I'm oversensitive or more attuned than most ADHD people, I take a light dose, which doesn't turn me into a productive robot machine going 1000 mph.

Stimulants follow a U-curve, and I wouldn't be surprised to know that most people take far too much and have to keep increasing their dosage. A single 30 mg dose makes my anxiety skyrocket, I usually take 20mg twice a day, I've recently experimented with lowering to 15mg twice a day and I think I like it even better.