So much of it depends on personality and situation. I wasn't even home full time and I felt completely trapped by children, marriage, expectations, burdens. An impending birthday party might have been the last straw. I went through a depression so bad it's only God's grace I didn't wind up as one of those stats of "mother kills self, two children." I was so deep in the situation I couldn't see how to change it. I thought about just running. I almost did. Almost walked out of the gym and kept walking. I would have had nothing with me (didn't take ID or money to the gym where it could get stolen) and would have disappeared in the ten minutes between when I finished early and spouse was due to pick me up.
I couldn't talk to anybody about it, either. There's too much shame to being such a bad mother that you feel like you can't face your kids in the morning, and you just want to leave. You hide it, and it gets worse and worse, and you wind yourself up in the morning with a happy face and stay on top of everything, and then you just...crack...
Fortunately for me, I got love and a life preserver at the same time as the little tiny thing that made me crack, and from then I crawled out of the pit. But not everybody is so lucky.