Erdos took amphetamines daily after his mother died in 1971, and claimed to sleep for about 4 hours a day while on amphetamines. He did not recommend them to anyone else, and he objected to the use of amphetamines being included in his biography because he didn't want to cause any kids to start taking drugs.

Erdos was also apparently more prolific after starting amphetamines, perhaps because he started sleeping significantly less.[1]

[1]: The Man Who Loved Only Numbers, Paul Hoffman, http://www.amazon.com/The-Man-Loved-Only-Numbers/dp/07868840...