"Oh I think I may have ADHD too!!" How do you respond to this???

For some reason I talk to people and disclose my diagnosis (only when it is relevant in the conversation and contextually appropriate), they love to say "I think I do too!" and idk but it's always off putting, at times then they will usually mention symptoms that on some level every person ever can relate to. I do not know how to appropriately respond to this lol. Part of me wants to be mean and challenge them, but I know I need to be polite. Though I don't always want to be necessarily affirmative to this behavior because they may take that as a sign of approval, even though my opinion literally shouldn't mean anything for I am not a doctor; but you know with the self-diagnosed running around they'll take what they can get. Of course, these people may actually have ADHD just undiagnosed, I only got diagnosed not to long ago and I was 24 then, so I get that (though I never told anyone I think I might have ADHD when someone told me they did....) and don't want to dissuade them from actually going to a professional for an opinion. Anyways, what is the best and most appropriate way to respond to this?