I am wondering the same thing with regards to my H. I really can't pinpoint any particular triggers now or when he really began his MLC as it was very gradual.
He did have a quarter life crisis about 10 years ago and so many issues he has brought up now (with regards to his self worth, career choices, etc.) are the same as back then, only seemingly magnified a ton. I often wonder if there was no end to the QLC and no beginning to the MLC, just one big journey. Granted, the first time around he didn't throw our M away or anything like that and it seemed short lived and he returned to normal for years, but he made a comment a few months ago about feeling like things got "swept under the rug" at that time. So now he is at a point where he can't ignore it anymore and he has to deal with them.
Like Cat's H's family, my H family has depression and bipolar so who knows how that plays into it, or has all along. I never did see him as depressed before, though.
