(((((krhea))))) IMHO I think that a certain amount of sadness/depression is a normal reality for women "of a certain age" : Hormonal levels contribute, Empty nest syndrome,aging, disappointments, addict sons/daughters, loss, etc. While I am not on meds and I'm not clinically depressed, some days I do feel down which never happened to me in my 20s 30s + 40s. Yes, I'll admit it, I am in my 50s.
Exercise and a healthy diet keep my faily peppy. I went to a therapist a few times.
I reach out to my friends for support, fun and adventure. I try to practive gratitude and take vacations several times a yr.
Before your friend mentioned this to you, had you been feeling different than usual.
Is it situational due to your son's status? I took a long bath yesterday with candles for the 1st time in yrs. that felt wonderful.