I've written before about being diagnosed at 43 with ADD. It came as a big surprise to me (and, later, to my sister, who found she had it too) because I had the wrong idea of what ADD (or ADHD) was -- I thought it meant you couldn't focus on anything, or read a book to the end, for instance. And I could sometimes hyperfocus so much that I would forget to do other things, like eat, or even go to the restroom.
Of course, I was ignoring the part of me that couldn't seem to get routine chores done. And there's the rub of ADD -- the chemistry in our brains are inefficient and sometimes even backward when it comes to concentration.
Daniel G. Amen, M.D., who has written 12 books dealing with ADD, has studied the brains of patients for years with his SPECT brain imaging. He takes pictures of the brain during different concentration tasks -- sort of like 3-D MRIs -- which allows him to see which areas of the brain are over- or under-functioning during specific tasks. He has broken ADD down into six basic types. Some people just plain have different attributes than others.
I can concentrate for days on something that interests me -- my brain turns on the focusing chemistry full force when I'm engaged. However, give me a checkbook, a repetitive chore or a boring lecture and I can almost feel the faucet turn off.
Some ADD patients seem apathetic; others can have issues with anger. Some ADD patients can read and enjoy entire books; others have trouble getting through a chapter and comprehending what they read. Some are extremely forgetful; others may feel like their thoughts are racing. Some stay quiet, so as not to call attention to themselves; others are quite talkative, and/or hyperactive. The important reason to be aware of different types, if you or someone you love has ADD, is because treatment can differ slightly, and dietary and nutritional needs can help smooth out the ride.
Here is an article from the AD/HD Information Library on different types of ADD (Classic, Inattentive, Over-focused, Temporal Lobe, Limbic System and Ring of Fire):
http://www.newideas.net/add_types.htm
And here's an article on nutrition and the ADD brain: