To answer your question: Not that I know of.
To waffle freely:
I believe it's lower than normal background levels of dopamine.
Obligatory disclaimer I am in no way a doctor or scientist. This is probably wrong. Pinches of salt all round. This is a theory I'm kicking around now and then but I don't have the knowledge to confirm/deny the hypothesis yet.
When a normal person tackles a regular task they'll get a little squirt of dopamine leading up to the task (anticipation) and then a corresponding signal when the task is done (I did the thing correctly, woohoo).[0]
When a normal person tackles a task and gets a better than expected result, they get a fresh squirt of dopamine upon completion (Oh wow, that went really well! I should consider doing this again!)
When someone with the ADHD-type brain wiring tackles a regular task they'll get the initial anticipation squirt, but upon completing the task they'll get a lesser amount (in dopamine language: that didn't go as well as I thought it would)
Compound that effect over $age years and you get someone with no real motivation to do anything, often distracted by random things that might be interesting, anxious, depression, imposter syndrome, all that good stuff - they rarely get a "I did good" signal, so nothing feels worth doing and they don't feel like they've had much success in life. Also might explain why a lot of ADHD folks have some sort of dopamine loop going on - alcohol, smoking, drugs, overeating, absolutely covering every meal in salt, etc. Something that brings up their background level of dopamine.
You do get positive effects from this - it's not all doom and gloom! - quick learners, jack of all trades, outside the box thinking, anything that might give a better dopamine response than the day to day routines
Might also explain all the "ADHD people were great as cavemen" stories that pop up now and then - nothing gives more dopamine than "holy fuck, I survived", the modern day doesn't really have many of those moments.
Feels like this would also explain why someone with ADHD can take stimulant medication and not bounce off the walls like a normal person would on the same medication - their background level of dopamine is being brought up to normal levels by the medication which in turn allows the rest of the system works as it does in normal people.
[0]: I actually found this theory while looking into AI stuff, haha: https://deepmind.google/discover/blog/dopamine-and-temporal-...
The quick summary from https://en.wikipedia.org/wiki/Dopamine
> Within the brain, dopamine functions partly as a global reward signal. An initial dopamine response to a rewarding stimulus encodes information about the salience, value, and context of a reward. In the context of reward-related learning, dopamine also functions as a reward prediction error signal, that is, the degree to which the value of a reward is unexpected. According to this hypothesis proposed by Montague, Dayan, and Sejnowski, rewards that are expected do not produce a second phasic dopamine response in certain dopaminergic cells, but rewards that are unexpected, or greater than expected, produce a short-lasting increase in synaptic dopamine, whereas the omission of an expected reward actually causes dopamine release to drop below its background level.