Originally Posted by CoffeeBeak
It can cause impotence later in life, apparently.
Masturbation has no negative effects whatsoever except when it interferes with other daily activities.
As for spazattack33,
You are 13, and your hormones are going crazy and they will continue to do so for the next 6 years or so. Get used to regular charges in sexual functioning because it probably become stable until very late teens.