As a member of the ADHD community, I can tell yeu it's quite, quite real.
I don't take any medication for it (and never noticed any change from the ritalin anyway), and it's not related to type, though some may be more prone than others I'm sure.
I can be midsentance and completely loose track of whot I was saying, my mind just drifting off on its' own. I TRY to do prayers, but over half the time is spent apologizing, and the rest is spent with a mind wandering so much it changes direction entirely every few seconds to the point I forgot I was even in prayer. I figure if there is a god, they must only put up with me for the sake of being so pathetically amusing.
Having multiple lines of thought going at once is the biggest issue, though, I find. I'll be thinking of a half dozen different things on different layers of thought at once, and as soon as a correlation between a few, or one looks shinier than the other, it's like... it's kind of like a train with several traintracks all next to each other, except where anyone else would have their train of thought on a single track, mine runs on about 6 at once, all next to each other, and it'll randomly switch between tracks without warning XD
If stuck with only one thing to focus on, it's pretty much impossible. It can't be done. More lanes of traffic will open on demand if I'm lacking other things to distract me.
As such, I've learned to deal with such... typing online is *SO* many times better than talking in person or out loud... it's easy to just scroll up on text and see whot I was talking about 5 seconds ago. Tapping my feet, listening to music, having the tv on, having a game of solitare going, AIM up and 4 - 6 people chatting to, browsing teh inturwebz and so on, I have all of these going at once when trying to do homework, otherwise I can't concentrate XD
The easiest way to prevent ones' mind from wandering, I've found, is just flood it with an abnormally large amount of background noise until it's too busy keeping track of so many things at once it doesn't have time to actually try to skip between them.
And as InsatiableCuriosity said, treatment can kill creativity. Creativity is the ability to see patterns that don't exist, and create yeur own new ones, while intelligence is the capacity to see patterns that DO exist. Having many layers of thought, and being able to browse all of them at once, and seeing or making up connections endlessly, can turn to such bizarre yet interesting masterpieces. To kill off this is to loose much of the ability to create intricate patterns out of thin air.
Such is the way of things though; madness is not necessarily a 'bad' thing, so much as it is often a form of the mind hyper-specializing in a task to the exclusion of all others, or looking at things in such a different manner, that 'normal' thought processes no longer apply. This can often lead to insights and developments many will overlook... but will also lend to issues regarding dealing with 'normal' thought.
Overall, the problem is vastly overdiagnosed. Anyone who gets distracted is branded ADD, even if it really isn't. ADHD usually involves adding in hyperactivity, usually of the body. Once again, this can be delt with by physical action; drumming fingers in a complex pattern, toe tapping in sequence between telephone poles as driving, so that yeu need to do a complex pattern between the poles without having yeur toes down when passing one, silly stuff like that. The need to move and 'do' is always present, but it can be channeled into other stuff easily enough if yeu know how to do it.
But yeah, I got off track again XD It is overdiagnosed, and I doubt that many people have such.
I believe, this is just personal opinion, but I do believe that it's often thought that it occurs "most commonly in children" is a myth... rather, adults usually have endured living with such long enough that they have found tricks and methods with which to negate, or at least lessen, the problematic areas, such as I have. Also, children in general are 'hyper' and easily distracted, which leads to even more false positives.
If it's true add/adhd, then chances are yeu'll never 'grow out of it', but will simply learn to cope with it, and mask its' appearance.
Anyways, no, I can't sit 'still', but I've found many ways to avoid doing so without it being obvious. Same with the attention span itself. There's a ridiculous amount of behind the scenes stuff going on in my head and occurring with my body, that most people will never know. It's the only way I've found to focus and lead a 'normal' life, but it works, more or less =3
Unless all distractions are removed... IE in bed in prayer, as mentioned earlier, when all the normal methods for coping mechanisms are lacking, then it becomes apparent just how bad it can be. Being unable to focus on a single thing for more than 15-30 seconds at a time can be crippling if not carefully managed.
Even so, there's always the extra layers of thought... yeu can drown a few out with distractions like music, or whotever method yeu choose to try to negate them, but they're always present. The same with body movement; it's always present, yeu just have the ability to override these layers of thought/movement with more subtle forms which can keep things slightly more managable.
Even so, it's still easy to jump from topic to topic, or become restless; read my posts in general and look for paragraphs and run on sentences where I'll follow a line of thought and it'll wander all over the place seamlessly without any real structure. I can LIMIT the amount of wandering to a great degree, but never truly repress it fully. It's to the point that the term "I digress" is irrelevant, since it's an all encompassing term now which may as well just be slapped down over the entire post or speech or whotever XD
Yeu want the easiest example? Any time I start a paragraph with "anyways" or "regardless", or anything akin to such? It means I intended for that to probably be the last paragraph and I was trying to wrap things up. Yeu'll often see 4-5 of these in a single post. This is where I just realized something else to say and wandered off over there and forgot to stop XD
Soooo yeah. ADHD is good and bad. I'd hate to live without it; I rather cherish my thought process, even if it does have its' drawbacks at times. Do most people KNOW I have such? Not really. I've gotten good at masking the fact, and restricting its' negative aspects, but it does still creep in from time to time. Even so, I rather think it's a large part of whot makes me who I am =3
That being said, it's still thrown about far too often as a term, and people who seriously don't have any issues at all are just called such because they may be distracted slightly. Bah!