Here's a bit of fact:
The REASON mary-jane (I can't spell it correctly. -grin- ) will affect your vitality is thus (also where the myth about Mountain Dew comes form. In some cases, it can be true.):
When the drug is finally absorbed into your body (ALL parts), it gets into the "bodies" of your sperm, making them extremely active. (( same for caffine). The sperm then begin to, for lack of a better expression, "swim around" a lot, and then tire and die very quickly.
They, in the end, do not have enough energy to reach the eggs - if you were trying to impregnate a woman. Poor little buggers die halfway there.
This is NOT and effective contraceptive, so do NOT try it.