I was officially diagnosed at 35. First time I even heard about ADHD was at 28 and it was because my coworkers/friends noticed the telltale signs and asked me to get it checked out. Of course I ignored them completely because I didn’t think it was that big of a deal.

I highly recommend looking at the talks by Dr Russell Barkley and his book Taking Charge of Adult ADHD. It’s a lot more than attention/hyperactivity. It was the emotional response + lack of functional working memory that really convinced me of how much it impacts my life and helped me understand why the attention issues occur in the first place.