By Melanie McGrath

Andrew Solomon is a depressive. Depression has made him nervous about showering (water too heavy) and afraid of lamb chops (too difficult to cut up). He has been dependent on Ambien, BuSpar, Dexedrine, Efflexor, Navane, Paxil, Serzone, Valium, Viagra, Wellbutrin, Xanax, Zoloft and Zyprexa. In a bid to rid himself of depressive symptoms, Solomon has seen psychotherapists, masseurs, crystal healers and had himself daubed in fresh ram's blood (you'll have to read the book). Over the past decade or so, depression all but killed Solomon, but it also motivated him to write this extraordinary and redeeming book.

Depression is not an easy subject and this is not an easy read. All the same, The Noonday Demon is too compassionate to be remotely alienating or depressing. Solomon is a meticulous anatomist of his subject.

Exhaustively researched, this is a work not only of great charm and individuality but also of impressive scholarship. In 500-odd pages Solomon elegantly cruises through the many contested definitions of the illness and moves on to case studies, scientific theories and their evidence, historical and literary description, research notes and interviews.

The minute autobiographical dissections of Solomon's own struggles with depressive illness ground the book in subjective experience, which is, in the end, the only definition of depression that holds true for all depressives. Nobody really knows what depression is, which probably explains why it is so widely misunderstood and why so many people, in the West and elsewhere, are left to suffer its devastating consequences alone.

Among the myths of depression are the following: that it is a Western, largely middle-class malaise; that it is exclusively a feature of modern life; that it is peculiar to humans; that it is a mental mirage (which can be cured, as one of Solomon's correspondents helpfully suggested, by 'doing things with yarn') and that there is nothing to be learned from it. Solomon debunks each of these (did you know, for example, that monkeys, rats, even octopi suffer depression?). By the end of the book you are left breathless at his rigour and clear-sightedness and, above all, by his humanity.

I was unconvinced by his chapter on the evolutionary function of depression (which seems to turn on the unsubstantiated guess that those who challenge the power hierarchy and lose become depressed and withdrawn, thus obviating the need to kill them or kick them out of the tribe) but for the sake of comprehensiveness I was glad to have it included.

Solomon is American and some parts of The Noonday Demon will strike a British audience as peculiar.

For starters, American psychiatry goes in for lurid and aggressive interventions. Psychopharmacologists in the US seem happy to prescribe complex cocktails of psychotropics to more or less anyone. One man was put on anti-depressants by his chiropodist. Solomon notes this trend but doesn't really develop a convincing argument for or against. His peculiarly American fondness for melodrama is bearable up to the point where he compares his depressed self to Dresden after the bombs. Is that tacky or what? And I suppose we have to forgive Solomon for such dreadful neologisms as 'modalities of treatment' but there's really no excuse for 'suicidality', is there?

These nit-picks aside, what I like most about this book is that it appears to follow the trend of upper-class misery narratives (begun by Elizabeth Wurtzel's Prozac Nation) while actually bucking it. And it is about time it was bucked too. Haven't we had enough of poor little rich kids and their woes?

OK, so Solomon is a bit of a poor little rich kid himself, but he has the grace and intelligence to see beyond his own circumstances.

If there is one persistent message it is that depression isn't a Modern Manhattan Malady, but an illness without class, geographical or even temporal boundaries. 'A long labour of the soul can produce melancholy,' said Hippocrates 2500 years ago. Some things never change.

You cannot fail to be humbled, moved and in some way renewed by The Noonday Demon. It is at once erudite, personable and profoundly challenging.