Self harm is a very unhealthy way to deal with stress, anxiety, and any other type of unusual situation. It can be very dangerous to your health and leave permanent damage on your body and soul. If you know anyone who is self harming be sure to tell an adult and be as supportive as you can. You never know what someone might be going through! :)
A person can possess a knife and a gun potentially becoming a murder
Try chewing some gum, of your choice,
don't use mouthwash for a bit (the alcohol can make your mouth drier)
reduce your caffeine intake, stay away from caffeinated drinks like coffee, and even soda.
I do think that mass hysteria can affect the environment because the hysteria can cause people to do something to the environment. I just recently read a story about mass hysteria causing people to spray everything with chemicals...it was interesting. But the chemicals would affect the environment.