I think (based on observation alone) currently the most common psychiatric diagnosis and co-morbid state is “anxiety.” Kirk has some good insight about it.
From Kirk’s Enemies of the Permanent Things:
“Anxiety” means distress of mind produced by prolonged apprehension of impending disaster. In our century, the dominant schools of psychology have arrogated the word as a term of pathology; and when many psychologists employ it, they imply that anxiety is apprehension without real cause: that is, a dread purely subjective, conjured up by the sufferer’s mental sickness.
But in truth anxiety is produced by disorder: disorder in private existence, and disorder in social existence. If the disorder which afflicts the anxious man is purely illusory, the product of his sick fancy, then anxiety falls within the borders of pathology; but if the disorder, internal and external, which the anxious man experiences is the product of a real moral and social confusion in his time, then the cure for anxiety lies not in psychiatric and physiological treatment,
but in a stern endeavor to lessen this real disorder—an endeavor best lightened occasionally by letting cheerfulness break in.
A condition of anxiety brought on by a demonstrably real decay of order can be alleviated only by a restoration of order—or, at least, by satisfying work toward such a restoration, both in the order of the soul and in the order of politics. Anxiety results from the collapse of normative belief, the dissolution of standards of private conduct and public justice. Before anxiety may be dissipated, norms must be recognized and obeyed….[I]t is essential that the sufferer from anxiety become aware of the reality of norms, and that he do something to signify his recognition of those standards, at least in his inner life, before he can be relieved from his affliction in any degree. Anxiety battens on fecklessness, impotence, frustration; it shrinks when conformity to norms restores purpose to a man’s existence.