The question is "how are you?"
Depending on my mood I would answer in a number of ways.
The first is "OK" or "I'm good". I may or may not be masking how I was really feeling.
The second response is "Ummm... I'm..." "OK... I think". or similar. This is a clue for other person to inquire a bit further. And means I am not 100% present.
There are other responses, but the one where I can stymie people is when I reply "that depends on whether you want a real answer or not".
We tend to gloss over how we are feeling, for whatever reason. Whether it be guilt or embarrassed, to be that odd person out who reveals their true self, is frowned upon. At the same time, I can speak openly and honestly to my psych. I can now (mostly) speak honestly with my support person(s).
In relation to MH, we probably don't admit to it because you are then the odd one out. Yet if you speak openly about it with other people, they will admit to similar problems. When I told some people about seeing a psych because of ..... they said that were on medication for X, Y or Z. Similarily with parents and other family friends. It we are honest with ourselves, we should be able to speak about it honestly without fear of being perceived as the CRAZY one, because that is how "we" might be perceived in the media. And because you cannot see it (MH), then does it really exist? We know it does, but it is not evident to those around us if they see us smiling.
But if we can be honest with at least our GP or psych, we have chance of making it to other side. Additionally, in being honest with your GP etc. means they get a true-er picture of you, and can prescribe the correct medication, whatever that might be. In being totally honest with my psych. means that we can examine the real issues rather then skirting around the margins.