I think its so outlandish to jump to that conclusion or even bring that up to a parent about there child unless you have seen that child in a professional setting.
Children are trying on all kinds of behaviors to see how they fit. They are also reacting to feelings they don't know how to articulate yet. That is an alarmist and cruel thing to suggest. Besides most mental disorders are an exageration of a more normal condition. Think before you dole out such a negative piece of advice