*it ruins your immune system (especially if you use it regularly, even once a month is regular)
*it ruins your endocrine system - any gland pumping vital hormones within your body may say "fuck you, I'm quit" anytime
*depression - do you think you know what depression is? No you dont until you've suffered mdma hangover
*there are also minor risks like having unprotected sex with unknown people while you're high
It doesn't mean you WILL have those symptoms, but there's a good chance you will, depending on your health condition.