Isaac Newton & Bipolar Disorder: the Breakdown of 1693

Isaac Newton was probably the most powerful scientific mind who has ever lived, and by every contemporary account a deeply strange and difficult man — solitary, secretive, vindictive in dispute, and capable of periods of work so intense that colleagues feared for his health.

In 1693, at fifty, he suffered a documented breakdown involving insomnia, paranoia and letters accusing close friends of plotting against him. What caused it has been argued about for three centuries.

The Working Bursts

The famous story is the plague years. When Cambridge closed in 1665–67, Newton returned to Woolsthorpe and in roughly eighteen months laid the foundations of calculus, developed his theory of colour and light, and began working on gravitation. He was twenty-three.

The Principia itself was written in about eighteen months of sustained effort in 1685–86, after Edmond Halley prompted him. Contemporaries described his working state during this period: his assistant Humphrey Newton recorded that he forgot to eat, rarely went to bed before two or three in the morning, sometimes did not sleep at all, and would leave meals untouched.

He also spent years on alchemy and on unorthodox theology, writing more on those subjects than on physics, with the same obsessional intensity and complete secrecy.

Between these bursts were long fallow periods in which he published nothing and, by his own accounts, achieved little.

The Breakdown

In 1693 something went badly wrong.

Newton experienced severe insomnia, described by him as going five nights without sleep, and lost his appetite. He wrote to the philosopher John Locke accusing him of attempting to embroil him with women and saying he had wished Locke dead. He wrote to Samuel Pepys in similar terms, saying he must withdraw from his acquaintance and see neither him nor his other friends again.

Both letters were followed weeks later by apologies in which Newton said he had not slept, that he had written without knowing what he was saying, and that he could not remember what he had written. Both men, to their credit, forgave him.

The episode lasted some months. He recovered, and afterwards left research largely behind — taking up the position of Warden and then Master of the Royal Mint, where he was ruthlessly effective, personally pursuing counterfeiters and having several hanged.

The Competing Explanations

Bipolar disorder is the most commonly proposed reading, and it accounts for the pattern: prolonged periods of extraordinary, sleepless productivity, alternating with fallow periods, culminating in an episode with paranoid features and reduced need for sleep.

Mercury poisoning is a serious rival explanation with physical evidence behind it. Newton conducted alchemical experiments for decades, worked with mercury constantly, and recorded tasting his compounds. Analysis of surviving samples of his hair has been reported as showing elevated mercury. Chronic mercury poisoning produces insomnia, tremor, irritability, memory loss and paranoia — the historical condition known as erethism, from which the phrase "mad as a hatter" derives.

Situational stress should not be dismissed. In the period before the breakdown Newton had lost a close friendship with the young mathematician Nicolas Fatio de Duillier, and he was in the middle of bitter priority disputes. He was also fifty and had been working at an unsustainable pitch for thirty years.

Autistic traits have also been proposed, based on his social difficulties, extreme focus and indifference to company. This is speculative in the same way all the others are.

So Was Newton Bipolar?

Unresolved, and probably unresolvable.

The strongest point in favour of a mood-disorder reading is that the pattern of intense productive bursts and fallow intervals is visible across his whole adult life, decades before the alchemy is thought to have poisoned him. The strongest point against is that we have a well-evidenced physical explanation for the specific 1693 episode, and one that fits its symptoms closely.

Our reading is that mercury is the better explanation for 1693 specifically, and that a cyclical temperament is a plausible but unproven explanation for the longer pattern. It is entirely possible both are true.

What we would resist is the tidy version in which Newton's genius is explained by mania. He did his best work in sustained, disciplined, extraordinarily careful bursts of reasoning, and mania does not produce the Principia. Mania produces confidence, not proofs.

Legacy

Newton's scientific legacy needs no summary. He also reformed the English currency, served as President of the Royal Society, was the first scientist knighted for his work, and conducted several of the most vicious priority disputes in intellectual history — particularly against Leibniz over calculus, in which he used his position at the Royal Society to rig the investigating committee.

He never married and by most accounts had no romantic relationships. He was buried in Westminster Abbey.

We include him because the question is asked frequently, and because his case is a useful demonstration of something this website returns to often: when a historical figure behaves strangely, the psychiatric explanation is only one candidate, and the physical ones are often better evidenced.

Frequently Asked Questions