Alexander the Great, as famed for his drinking as for his military exploits, was driven into out-and- out alcoholism by his over-demanding parents, according to new research by an American historian.

John Maxwell O'Brien, Associate Professor of History at Queen's College, City University, New York, bases his theory on a three-year study of modern alcoholism in New York. His findings will be published in Britain this month, in Alexander the Great: The Invisible Enemy.

The book suggests that the Macedonian king, who built an empire stretching from Greece to India in only 10 years before dying at the age of 32 in 323 BC, turned to the bottle to escape personal inadequacy.

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Alexander's drinking bouts are legendary: in one, he killed his friend Cleitus, who had saved his life in battle, with a spear. Alexander was so remorseful that he wept for three days. But no modern writer has previously linked Alexander's drinking directly to his increasingly degenerate behaviour - which is usually ascribed to the corruption of power.

'In the last seven years of his life, Alexander became increasingly unpredictable, megalomaniacal, and paranoid,' Professor O'Brien says. 'He was driven to extremes of behaviour, followed by intense remorse.' The New York study showed that these are all the classic symptoms of alcoholism.

His alcoholism killed him, the professor argues. In a feverish state, he insisted on drinking a huge quantity of wine to slake his thirst. A few hours later he was dead. 'His insistence on wine - rather than water - only makes sense if the fever was an acute case of alcohol withdrawal.'

The New York study also found that the root cause of alcoholism is insecurity, and Alexander again fitted this pattern. His was caused by his parents, says the professor. His father, Philip II, was sarcastic and unpredictable, deliberately keeping all his associates and son in a state of unease.

Alexander's domineering mother undermined his sanity by telling him that his real father was not Philip, but a god. 'Alexander's escape into alcoholism and desire to conquer the world were two sides of the same coin - uncertainty about his own identity, and a desperate desire to prove himself,' Professor O'Brien says.

His theory is challenged, however, by other historians. Dr Simon Hornblower, of Oriel College, Oxford, says that many of Alexander's contemporaries thought he drank too much, but there is not enough medical evidence to prove he was an alcoholic: 'He may just have drunk through boredom.'

Alexander the Great: The Invisible Enemy (Routledge, pounds 25)