ADHD andDopamine | ADHD Information

What have doctors told you,. is ADHD caused by a lack or an overabundance of dopamine neurotransmitters?

I've found evidence for both, which is startling, no?

My doctor never tried explaining it, and I never asked for an explanation, since there's plenty already written and available in library books and on the web.  My understanding, from what I've read, is that there is less dopamine and norepinepherine available in the ADHD brain.  This seems to be borne out by the effectiveness of medications which inhibit the functioning of cells in the brain that take both of these neurotransmitters out of circulation, making them unavailable to perform their function (which, among other things, is to promote alertness, focus and attention).   Other ADHD meds cause more of these neurotransmitters to be released/produced in the brain, providing the same net effect: greater availability of these neurotransmitters, allowing the ADHD brain to function more like a "normal" brain functions.