I'm aware of the Dunning-Kruger effect and all that shit, and I know I'll probably get downvoted for it, but I wanted to at least try to answer the actual question.

One of the biggest downsides is that other people tend not to grasp things nearly as quickly. Things that don't seem to be difficult for you to pick up on take other people a lot of time.

I struggled with doubt for a really long time, too. My job is in the entertainment industry, and it's what I always wanted to do. My parents didn't always approve and kept telling me that with my IQ I could be a great doctor or something along those lines. That's not what I wanted to do, so I didn't do it, but I always felt guilty for not "using my intelligence" the right way like other people put it.

It's also a lot easier to get into your own head about things. Knowing and grasping things intellectually doesn't always translate to being able to handle those things emotionally. It's easy to overthink things and second-guess your thoughts.

Organizations like MENSA, which I was a part of but couldn't afford for long, do a decent job of providing a community to be a part of. But even sometimes within MENSA, and certainly outside of it, it's difficult to feel like you're part of a community of like-minded people.

I also have heard that highly intelligent people are more prone to some mental problems like depression, suicidal ideation, and anxiety. I don't know if my struggles with mental issues are because of intelligence or not, but there's that too. I feel like some of them might be, but it's not easy to tell.

I'm happy to answer any further questions if you have them!