There is a diel cycle of cortisol in diurnal mammals which peaks in the morning, hypothetically to give us energy to kickstart our day.

Yes in fact in humans there is a maximal peak on waking followed by a smaller peak around lunch and another large peak towards evening.

This graph depicts baseline cortisol, of course. You were mostly talking about increased levels of cortisol.

Yes and one of the theories is that pathology occurs when the "variability" and fluctuations disappear due to consistently raised levels.

One of the main things to stress when discussing stress (pun intended!) is that it's still not really clear if it's a good or bad thing, or rather how much is good or bad and what a "good" baseline cortisol level is

Yes for sure. I would suggest it is one of those things where you need a certain amount of it to function in a normal and healthy manner. It spurs us to action. Cortisol is also not bad (although the press likes to suggest it is) - without it we would die very quickly. Like many things it is a matter of balance.

I've been thinking about writing a post about stress for a while, and may start with that topic!

You should!

Thanks for the excellent, rigorous post!

Thanks for a fantastic response:)