My theory is that Shakespeare, genius that he was in his understanding of humanity, portrayed in Hamlet a man with manic depression centuries before manic depression was labelled.

Presumably the condition was around before the psychologists described it; I don't see why Shakespeare couldn't have noticed it among his acquaintance (actors and writers are very prone to the condition).

Melancholia was a term in widespread use in Shakespeare's day, and he gave us a straight melancholic personality in Jacques in `As you like it'. Hamlet is certainly melancholic much of the time, and his speeches portray the two most obvious symptoms: suicidal thoughts, and lassitude -- inability to do what he believes he ought to do.

But Hamlet also shows signs of mania: his variability of character that perplexes people; his considerable energy that comes in spurts while at other times he is hanging around moaning; his courage (or recklessness) in going off with the ghost; the way he gets utterly wrapped up in the production of `The Mousetrap'; his unthinking action in stabbing someone through the arras without checking to see who it is; his sporadic brilliance, charm and wit; and the way that we are never quite certain how much method there is in his madness.

While these aren't necessarily what a modern psychologist would pin down as symptoms of mania, a lot of them are recognisable to anyone who has lived with manic depression, either as the person who has it or who lives with a person who has it.

OK. Some doubts about my theory.

-- There is a well-recognised tendency to read into Hamlet our own characteristics. He is Everyman, and every man and every woman can find something in his character that matches their own. I have manic depression, so maybe I'm just doing that.

-- I may be making the same mistake as Oedipus Shmoedipus in reading modern psychological theory into Shakespeare's characters.