I hide my severe depression by acting just the opposite... smiling, making jokes, acting upbeat and bubbly. Lots of people that know me have NO CLUE that I have been suffering from suicidal ideation and severe depression. Interestingly, I teach psychology. When we were talking about depression, I had my students raise there hands if they knew someone that was suffering from depression. Of course they all "know" me, but only a third of the class raised their hands. I let them know that they all probably knew someone who was suffering from depression, but they were just unaware of it. I let them know some statistics and encouraged them to be kind to all people, because you never know who is going through a battle you can't see.