What are common symptoms of mental illnesses?

There many, many mental illnesses out there. My aunt has ADHD, a mental disorder that renders her incapable of concentrating or staying in one spot for awhile. My father went to college with a boy who had Tourette's Syndrome, a mental disorder that forces the victim to shout out words for no reason whatsoever. A boy at my high school has ODD, a disorder that makes him of a more aggressive, bullying type. If you're talking about insanity, then you may see MANY different characteristics in different people. If you suspect you have ANY mental disorders, then talk to a psycologist. Remember that it's their job to find out what's wrong, and it's also their job to listen. You don't have to tell anybody, and nobody will ever know.