How do people mask their nervous breakdowns?

Do they act noramally? or do they do something to conceal it from you? so you think that nothing happens to them.How do people mask their nervous breakdowns?
I conceal it by doing something else like play cards or act like I'm reading, but sometimes it doesn't work well and people notice something is wrong.How do people mask their nervous breakdowns?
I think that they withdraw. Any interaction will expose their confusion. I'm holed up in my house typing answers to YA questions. So, you would never know what's up with me.
Some do it using drugs %26amp;/or alcohol.
Most of them are pretty normal so they don't have much mask. Basically they were over pressured but found they could recoup more so than they expected. Sometimes they use special strategies like listening to a portable CD player when in public, if it makes them more comfortable.
I think if they can, they try to act normal. Some people can hide it part of the time. I think if you are around them enough, you will see it.
Well, if they are having a nervous breakdown, they would be breaking down, which wouldn't look normal. Leading up to the breakdown though, some people will act normal - and the breakdown will seem to appear out of nowhere. I guess it can be different for everyone...and there are so many reasons why they will breakdown. One minute you know everything about them, and the next, they're a complete stranger. Kind of strange.