I heard some one say that if you took all of the characteristics of a typical healthy teenageer it would qualify for inclusion in the DSM as a mental illness.
As a mom of a teen I say they are completely crazy but not mentally ill.
Hehe.
Some psychology books on prejudice tell the story of an experiment that was done in the summer of 1954, where two groups of 11-year-old middle-class boys were invited to a summer camp. The experiment was meant to investigate the effects of competitiveness and co-operation. The place the experiment took place was called Robbers Cave.
Each group spent the first week going hiking and swimming together and doing other enjoyable activities, so they became friends. They gave themselves group names and printed them on their caps and T-shirts. Neither group knew of the others' existence at that point.
But then they were introduced to each other, in an atmosphere of competition. Football and other sporting events were arranged between them. The winning team of each event was given points. A trophy and medals were promised to the overall winners of the games.
Almost overnight, the groups turned into hostile enemies, and their rivalry escalated into a series of battles. Group flags were burned, cabins were ransacked, and a food fight that was like a riot erupted in their mess hall.
Bear in mind that these boys had before always been considered well-adjusted and decent. They weren't street gang members. But the man who planned the experiment commented that a naive observer would have thought the boys were "wicked, disturbed and vicious".
That just shows how people can behave in more extreme ways than usual under different types of pressures. Perhaps one reason people can be more argumentative than they normally would be on the Internet is that people tend to express opinions they wouldn't in ordinary conversation, so the provocation is greater.
As the stories about the development of multiple personality disorder that were told in the articles I linked to before illustrate, people can go from coping with life fairly well to neurotics who can't seem to cope at all under the wrong type of therapy.
(The story about the boys in the experiment has a happy ending. It was difficult to bring the groups together in friendship for a while. First, the organisers tried saying nice things about each group to the other, but that didn't work. Then, they brought the two groups together under relaxed, non-competitive circumstances, but that didn't work either. What did finally work was giving the two groups things to do together where they had to co-operate with each other to achieve goals they both wanted to achieve. For instance, the experimentors arranged for the camp truck to break down, and both groups were needed to pull it up a steep hill. Those activities worked wonders. At the end of their time there, the two groups were so friendly they wanted to travel home on the same bus.)