For me sleep deprivation puts my amygdala (the Lizard Brain) firmly in charge. Let the bad decision making begin! Let the anxiety flow! Which leads to more sleep deprivation.
I recently ceased to work in any form past 7pm (Lizard Brain anxiety behaviour), and refused to expose myself to glow of tv/computer/ipad/iphone screens starting at the same.
Where I used to toss and turn until midnight I now fall blissfully asleep by 10–10:30pm. I also stay away from alcohol past dinner during the week.
Best decisions ever. What I thought was mild depression was lack of sound sleep.