Andrew Huberman· PhD
During this phase of the day, because of the circadian shifts in our biology, the amount of dopamine and norepinephrine that's circulating in our brain and bloodstream tends to start to come down and levels of cortisol tend to start to come down. That's the ideal circumstance. ... 9 to 14 hours after waking dopamine and norepinephrine and cortisol are starting to taper down, just naturally. And a different neuromodulator, serotonin, is starting to rise.