Latecomer to this post, but I’m practically an old man of tabletop RPGs and lordy Moses, yes, D&D can be massively draining. Fun, but draining.
In my experience, the biggest problem I have is remembering all the rules and all the various bits and pieces you carry along with you. It feels like there are a thousand books of rule expansions and updates and errata and god knows what else, and then there are house rules and exceptions, and then you have to remember all the different items or spells and if this gives you a bonus against that or if your character has a racial bonus against ogres, oh, and by the way you have to remember the blessing that the cleric gave you and if that stacks with the potion, and you’re carrying the Great Sword of Boogly-Boo that does the thing but only every other Tuesday and OH MY GOD!!!
Yeah, that’s hard even without ADHD. Me and my friends would usually get to the end of a couple of hours’ session feeling like we’d been on some week-long sleepless challenge.
D&D is, I hate to say it, absolutely one of the worst for trying to remember every little detail. Which is a shame, because there’s a lot to love about it. I’d recommend looking into a couple of the more rules-light games that are around, like Savage Worlds or FATE.
Or if you’re more into the storytelling and character acting (like me) I can’t recommend highly enough Fiasco, which is more like a theatre sport or collaborative storytelling mediated by dice rolls, and generally winds up absolutely terribly for all characters involved. It’s great, and can be incredibly good fun if everyone completely throws themselves into this Coen brothers-influenced mess of people with great ambition and poor impulse control. So long as you don’t mind the idea that most, if not all, characters are likely to end up dead or in prison by the end of the story.
Funnily enough, the last time I played Fiasco I came out feeling super-energised rather than wiped out. I wonder if that’s an ADHD thing?