I think part of life is experiencing mental pain, and yes everyone will suffer that...in some situations it would be very strange not to experience mental pain even if you're a mentally healthy individual.

However I doubt most people have a serious diagnosable mental disorder/condition/disability or whatever that they have to live with every day. Though there are certainly plenty of things going on in the world and societies that certainly contribute to mental illness and can cause increases in it....but not everyone develops mental problems from those things, some people develop more physical stress related problems than mental ones, some get a lot of both.