One of the main reasons some of the stimulant meds don't work effectively is that they don't cover every essential neurotransmitter system necessary for efficient pre-frontal cortical communication.
Prevalence missing: Using the same, outdated DSM-4 [Diagnostic Statistical Manual] criteria, with even more disturbing diagnostic limitations for ADHD recognition encouraged by DSM-5, the problem is global.
Emerging research also implicates the neurotransmitter glutamate in the development of ADHD, likely due to its interaction with dopamine and norepinephrine.