[Curmudgel]

>The information about amphetamines made an impression. His friends at times tried to discourage him, but he claimed that without them, he could create no mathematics. Given his colossal output, this means that a significant part of the landscape of modern mathematics owes it existence to this drug.

Erdős was a heavy user of many other stimulants (like coffee), but only started to use antidepressants and then amphetamines in 1971 when he was 58 after his mother died. He was already established as a first rate mathematician (he should have won the Fields Medal), and using amphetamines to work 19 hours a day was his way of coping with the death of his mother.

See http://www.untruth.org/~josh/math/Paul%20Erd%F6s%20bio-rev2.... for more.