One negative effect is doing drugs because it is bad for health and many people die from lung cancer on top of that. some kids may do it because of peer pressure and just to fit it.
another negative example is abusive realationship if someone is dating another you should watch out for them being abusive. they might convince the other to do things they don't want to. an effect is if its a girl she can end up being a pregnant teen and the father may not want to be involved leaving the girl all alone
What stages? What people? I need the bigger picture to help you.
It can increase the heart rate up to three hours
hope this helps
