That very concrete, literal thinking is common with ADHD (and “high-functioning” autism). It takes a lot of time, but that can soften. My son is 15 now and does a lot better with at least trying to see and understand things that aren’t so literal. He can finally decode many figures of speech and recognize when a phrase isn’t supposed to be interpreted literally.
When he was 6 or 7, I mumbled under my breath in the car one day, “You’re gonna be the death of me.” I was obviously frustrated over something. He heard me and cried for a long time. He said, “I don’t want to the be the person who kills you, Momma. I love you.” We are far from that level of literalness now, thank goodness.
Jessica McCabe has a YouTube channel all about being an adult with ADHD. The videos are great! Also, there’s a website called ADDyteen started by a teen with ADHD (who is now a college student).
ADDitude Community Moderator, Parenting ADHD Trainer & Author, Mom to teen w/ ADHD, LDs, and autism