Sleep and depression are two things that are actually related. Here's an example.
At work, I have asked a colleague why she seems to be not performing well compared to her previous months. She said that she had personal problems that made her uncomfortable to go to work. She's having a hard time sleeping because of this and her performance at work got affected.
I cannot ask more information that what she said but I told her one thing - thinking so much of the problem will not resolve anything. There must be action on this kind of situation rather than clouding your mind with thoughts that cannot provide any solution.
Also I told her that she should take good care of herself and we need her to work well. First step is to have a ample sleep, eat well and positive outlook in life. If something's bothering her, she needs to face it, armed with enough strength and unwinding pursuit. It was never been easy to be in a situation like what she had. But it's a battle that she needs to work on. Being depress will just destroy her well being. It will not hurt to try and change her mindset about what's happening with her.
She took my advise and I told her that we will talk again by next week to check if there are any improvements on her condition and her personal concerns. The following week, she happily approached me and told me that I'm right, she realized that the real problem is actually her, she made wrong decisions and now she's tarting to correct it one instance at a time.
We are so blessed with the life that we have, so never give up. Depression is not a solution , taking good care of oneself would be needed for us to take good care of the others that matter to us.
Sleep more, eat well - Live life!