Effects of drugs on behavior: paranoia, aggressiveness, hallucinations, addiction, impaired judgment, impulsivity, loss of self-control. Drug and alcohol use affects almost every part of the body, from the heart to the intestines. Substance abuse can cause abnormal heart rates and heart attacks, and injecting drugs can cause vein collapse and heart valve infections. An addicted person devotes more and more attention to acquiring drugs, finding ways to use them and hiding them from others.
All these behaviors separate us from anyone who doesn't participate in our addiction, makes it possible or, at least, denies it or is willing to look the other way. One of the first goals of getting help for substance abuse is to break that wall of isolation. Knowing that they don't have to fight the battle alone is a relief for almost anyone caught in the throes of an active addiction. If you find yourself involved in an addiction, challenge yourself to break that isolation.
Tell the truth about what is happening to someone you can trust. If you see someone you want to isolate and suspect that they might need help with substance abuse, give them a signal that you're in a safe place. He's willing to listen without judgment and to help if he can.