I used to say migraine or flu back when I didn't understand depression and thought I was just horrible, not actually sick.
Now it depends. If I have to take more than a couple days off and need a note from my shrink I'll say mental health issues, or just health issues and they'll see psychiatrist on the doctors note. I'm done lying and hiding my issues. I don't go out and tell everyone I have a MI but I'm so done with lying, it just makes me feel worse about myself. It's sad reading the previous posts about how everyone lies.
I actually have to email my supervisor right now for time off and I'm terrified. I've pushed myself for months with depression and horrible anxiety but now I have officially snapped and wouldn't be able to function at work. I'm going to be honest with her "health issues, can't function at the moment etc." I know I can't work and it's no different than if I had a horrible physical illness, but I still feel scared admitting it to her. Most of my employers have been super supportive and I haven't taken much time off work, but you never know when you'll get someone who doesn't understand MI.