There are many informative articles to read here. In addition, before I found this site, I spent a lot of time on the site "The Storied Mind". I think you would find it an interesting site as it explains in detail, the link between depression and the "urge to leave."
I found so much info there, that I used to copy pages of it and give it to my MLC partner to read. It didn't "wake" him up, but was very interesting to read.
Basically I think the depression causes such pain that they just want to feel better and reach out to whatever they think will take away the pain, or the numbness they are experiencing. Could be drugs, alcohol, gambling. For many of us, it was the OM or OW, they turned to.
To the MLCer of course, we are the cause of their misery....if they could just get away from us, life would be so much better....or so they believe. Not true of course, but they have a long way to go before they will realize we are not the cause of their Misery.
Others will be along with more info for you.