> Do you have a deficit of dopamine, serotonin and norepinephrine?

What evidence exists that points this is the cause of ADHD? Wouldn't a dopamine deficit be more akin to Parkinson's Disease?

Also, last I remember reading, I am pretty sure we are not fully aware of why stimulants help people with ADHD. I think the leading hypothesis is that dopamine plays a role somehow, but I thought that he yet to be fully observed.