I'm married with two children and I can assure you that not only has my mental state slipped because of the stresses of home life, but I also lost an enormous amount of social activity that I intentionally maintained in order to keep my brain and health at optimal levels.
Not trying to one-up you here as having a family brings different forms of stress I can't speak to, but it's really hard to go for a week without interacting with another human being. Social connection is core to who we are as humans; cutting that off is like removing a limb.
It's interesting, family meets a distinct need. I've started working with technical peers and it's wonderful to be with others who can stretch your understanding, even just know what you're on about if you talk technically.
Entirely different to the mentoring, caring, parenting, intimate interactions with kids (and my wife).
I am OK, but my productivity is toast.