depression is a physical condition where you won’t be able to sleep. Like five days in a roll and because of it, you can’t improve your work performance even if you want to. The only wish you have is a good night sleep.
I had it, couldn’t sleep well for a month. My ex girlfriend had it, she couldn’t sleep for 5 days.
Many (most?) depressed individuals do experience sleeplessness, but that's not at all universal.