Dr. Matt Walker

And what better place to spend if that's your mentality than this thing called bed?

I just don't want to get out of bed.

I'm just going to stay here and lie in bed.

I'm awake.

I'm not asleep.

And so we don't quite know yet if depression is a condition that is associated with long sleep.

We certainly know it's associated with short sleep and disrupted sleep or that is masquerading as this thing called hypersomnia.

But when you really look at the data, it's not quite so clear.

That was the first peculiarity in depression that there could be this paradox of yes, long sleep, but also not enough sleep, too short sleep.

One of the earliest findings in depression and sleep and has been quite well replicated is a change in REM sleep.

But now it wasn't necessarily that individuals who had depression slept or had excessive amounts of REM sleep.

They had a little bit more.

What was interesting is that when that REM sleep emerged during the night was much earlier.

And in the first episode, I was telling you that when your head hits the pillow, you go down to the light stages of non-REM, then into the deeper stages, and then maybe after about 50, 60, 70, 80 minutes, you'll pop up and you'll have your short REM sleep period.

But that first REM sleep period in people with depression seemed to have been called up by the brain, abnormally or not, much earlier.

So it's what we call REM sleep latency.

From the moment that you fell asleep, what is the time, what is the latency of the first arrival of REM sleep?

And that REM sleep latency was significantly shorter in those people with depression.

REM sleep was arriving earlier.

Now it's hard because you can argue, and these are the most dangerous hypotheses, you can argue both sides of it.