Hi EZ, I am new to this forum, but I believe that some form of mental illness can trigger or at least contribute in some way to a MLC.
My husband also exhibits very bi-polar tendencies, and has suffered one or two severe bouts of depression in his life, one almost suicidal. He has always shown the the happy mask to the outside world, where as I got the "real" him, which I believe was always in a low level state of depression. After much urging from me he did attempt counseling a few times, and tried anti-depressants 2x, both times I saw a remarked difference, but he stopped both times on his own after a few months declaring they weren't helping. Right now he is definitely in a manic state and I fear what will happen when he actually looks back and really sees the path of destruction he has left, if that will trigger a severe depressive state, but not of a productive kind. I have just tried to position friends and family members that he knows, respects and looks up to to be around him so if he is ready to reach out for help, there will be someone there. I know that person can not be me.
I believe that certain personality types are more prone to severe symptoms of MLC, and I think having some form of even a functioning mental illness is one of those characteristics that make them more susceptible. I come from a family of mental health professionals, and they agree.
Meantime take care of yourself and know you can only do so much. Your husband has to want to take the steps to want to change, get help or deal with whatever is going on with himself. Its all up to him, and I know how frustrating that can be when you want to help so bad but can only watch them self destruct.
A Blessed Christmas to you and your family during this time.