Multi tasking is a myth so dont try to use your phone while driving.
facilitating, monitoring,providing and realizing
The brain gets used to you taking the drug. Some drugs will affect your neurotransmitters, or messages that get sent to your brain that regulates how we think or feel. You will eventually become dependent on the drug so if you stop you might feel sick or go through "withdrawal". Which people dont want to go through so they will continue to take the drug.
