Between someone who has ADHD, and someone who's just disorganized? Or forgetful? Or impulsive? Or has a short attention span? Is it the severity? Is it that the person with ADHD truly can't help it? Is there some kind of physical test that can tell if you have ADHD?

What I'm wondering basically, is how do you explain ADHD to someone else (someone who doesn't know much about it)? I won't know if I have it until I see a psychologist, but I worry that if he/she does diagnose me as having ADHD, that there are people in my life who will just not believe it. I worry that they'll say I'm just a disorganized/forgetful/lazy person who hasn't tried hard enough. And I worry that they may be right.