Erdos took amphetamines (speed, Adderall, etc), not methamphetamines. They are related drugs, but meth is much stronger and dangerous.
Take Galois, for instance (http://en.wikipedia.org/wiki/Galois). Solved one of the major mathematical problems of his time. Founded a major branch of abstract algebra (seriously -- in a three quarter grad level course, you spend about a quarter on it).
Died at 20.