Ghost of a flea

Using brain-imaging techniques, researchers have found that meth's toxic chemicals eat away at brain tissue, eventually robbing addicts of the ability to feel pleasure without the drug. With each hit, meth changes the way the brain works, impairing judgment, giving rise to psychosis and aggravating any existing mental illness, Rawson said. Meth also boosts heart rate, blood pressure and respiration. Over time, a user's eyes and mouth dry up. Teeth fall out. The body stops craving food, and only wants meth.