Are you confusing Autism with ADHD? Apparently Einstein and Newton had autism:
http://news.bbc.co.uk/2/hi/health/2988647.stm
ADHD is more debilitating, you CANT focus, your thoughts are going a hundred miles an hour and you have a constant need to move.
Actually you and Joxer are both right.
There's 3 different classifications of ADHD.
1) inattentive type
2) hyperactive-impulsive type
3) combination type
The latter 2 is what most people think of when they think ADHD, and @joxer; is referencing the 1st type (which is what I have). This is also why I went un-diagnosed for such a long time, since it's not your typical "template" ADHD situation.
ADHD is mainly a problem in the brain to create sufficient levels of dopamine and norepinephrine, present in most "normal" brains. It's a required system in the brain, since it creates a "reward" to perform regular functions. Without it we would just sit around like zombies. For people with ADHD, they don't get sufficient levels of dopamine/epi to perform normal tasks. In order to feel fulfilled, they need to find tasks that excite the brain enough to create those chemicals. It's why they can hyper-concentrate on something that's enthralling, because only then are they pushing those motivation chemicals in their brain they're normally being deprived of. It's also why they leave things until the last minute to complete (a long time to finish something doesn't create enough dopamine, but a panic induced rush to finish something will push enough epinephrine and dopamine to stimulate the brain). This area of the brain is also responsible for other executive functions such as inhibitory control, and and working memory. In other words, short term memory, self-control and concentration is "damaged", although that's still a controversial word. This is why those with ADHD get highly addictive to things easily. Food, porn, drugs, alcohol, risky behaviour, etc that can create more pleasure/reward chemicals past the norm. It's also why many people with Binge Eating Disorder make up a large portion of those with ADHD.
For myself, i've always been weary of using medication for treating symptoms, rather than healing the cause, but in this case I see it as brain damage. Again that's not a good word, because i've functioned, got through school (barely, which also now explains why school was hard but college was easy), and kept all my jobs. My relationships are another story. Using a sudo-amphetamine in small therapeutic doses like i'm doing now is not my long term plan, but it's giving me the tools to prepare myself through Cognitive Behavioral Therapy, natural supplements, diet change, and organization.