the accidental foot-in-mouth

Not too long ago I was talking on the phone to my mother-in-law, and I made a remark, innocently enough, that I had to keep an eye on the children "because depression runs in both sides of the family." I didn't think that was offensive, since I was putting the Sober Husband's family on the same level as my own family and because the very first time I met her, my mother-in-law had referred to two of her close relatives as "always so depressed", but my mother-in-law took quick offense.

"Who in my family are you saying is depressed? Are you talking about my mother? Because towards the end of her life, she really learned how to cope with her depression," she said hotly.

I was surprised that I had said something upsetting and said weakly, "Well, yeah, and [Close Relative]."

My mother-in-law said combatively, "[Close Relative] is not depressive! He's a sociopath!"