Newton, autism and mercury

Sir Isaac Newton was one of the most famous scientists the world has known. His remarkable life, during which he discovered the calculus, the nature of white light and the theory of gravitation, is outside the scope of this book. What is of relevance is a short period of his life, four years after this portrait of him was made, when he went mad.
During 1692-3, at the age of 50, he withdrew, accused friends of plotting against him, slept little, and reported conversations that did not exist. There have been several theories as to why he might have gone through this period of “short-lived lunacy”, one of which was toxic metal poisoning. It was before and during this period that he laboured late into the nights on his alchemical experiments. We know from Newton’s own diaries that he worked with mercury: “after I had stirred the mercury and salt together”, he wrote, “I put it on the fire to evaporate. The salt flew away quickly and left the mercury congealed in a hard rugged lump.” He also tasted this highly toxic metal, describing it as, “strong, sourish ungrateful.” He even joked later in life that his hair had turned prematurely grey because of his experiments with mercury.
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This theory received a huge boost in the late 1970s when a chemist, along with a historian, managed to obtain samples of Newton’s hair, which they then tested – finding mercury at concentrations nearly 40 times the normal level. Newton appears to have gone through a
short-lived period of madness as a result of mercury poisoning.
However, the story does not stop there. Professor Simon Baron-Cohen, head of the Autism Research Centre in Cambridge, has described Newton as having many signs of Asperger’s syndrome, a form of high-functioning autism. Newton’s lack of interaction with his colleagues and friends, bad temper, and such extreme obsession with his work that he often failed to eat or sleep, are typical of the syndrome. As autism and Asperger’s syndrome were not identified until over 200 years after Newton’s death, he could not have been diagnosed during his lifetime. But could Sir Isaac Newton be the fist case of mercury-induced autism?