From The New York Times:
A college student becomes so compulsive about cleaning his dorm room that his grades begin to slip. An executive living in New York has a mortal fear of snakes but lives in Manhattan and rarely goes outside the city where he might encounter one. A computer technician, deeply anxious around strangers, avoids social and company gatherings and is passed over for promotion. Are these people mentally ill? In a report released last week, researchers estimated that more than half of Americans would develop mental disorders in their lives, raising questions about where mental health ends and illness begins.
In fact, psychiatrists have no good answer, and the boundary between mental illness and normal mental struggle has become a battle line dividing the profession into two viscerally opposed camps.
More here.