Naps of 90 minutes or less and non-sleep deep rest protocols can increase dopamine and improve mood, focus, and alertness.

“The other reason is that the data on things like non-sleep deep rest and naps in the afternoon-- and again, the rule here is that you don't have to nap. But if you want to nap, it's been shown that naps of 90 minutes or less or non-sleep deep rest protocols... that those can all lead to increases in one of the catecholamines at least, which is dopamine. That's been shown in a really nice neurotransmitter labeling study, not from my laboratory, but from another laboratory, but also can improve mood, focus, and alertness on its own without the need to ingest caffeine prior to going into those states.”