One thing you might try is to simply write down the darkest deepest most depressed stuff on the plain sheet of unadulterated paper as if it was a journal entry or a technical paper, nothing fancy yet.
Now let it sit over night (or longer) and then without reading it over and over start journaling OVER it, do your designs over the words, choose random or not so random words to leave uncovered but paint, draw, glue, alter the page so the words no longer have power over you.
Do it over and over with different pages, leave a sentence here or there or do single words picked out of the writing to make a short poem that has nothing to do with the original subject. Take the words that tear up your mind and hide them, incorporate them, work with them til they have no power.
Lenny Bruce (60's comedian) once said if the president were to go on tv everyday and say racial slurs like "kike kike kike kike kike kike...jew jew jew jew jew jew" all night long everyday for a year those words would have no meaning any more, they would just be WORDS, Sounds.
I suffer depression and yes I have done this and yes it helps.
Great idea, and I'm glad to hear it helps. I suffer from depression too, and I usually rip up my darkest stuff because I don't want to preserve it in any way, but what you say about it losing its power is intriguing.