Does cannabis cause impotence?

Smoking ANYTHING can cause a reduction in blood flow. The longer you smoke, the more at risk you are of causing permanent damage to your blood vesicles, as well as your sperm count. Does this happen every time you get high, or is it an isolated incident? Do you have a hard time getting an when you don't smoke? If so, you may have poor circulation, causing your impotency. If it's an isolated incident, it could be your bodies way of telling you to lay off the weed, or maybe it was just a bad day.....