Many athletes throughout the world illegally use anabolic steroids in order to have an edge on the competition.
Most heroin users who use the drug regularly are incapable of concentration, learning, or clear thought.
Nicotine withdrawal symptoms can include irritability, anxiety, depression, headaches, fatigue, disturbed sleep, increased appetite, and an intense desire for nicotine.
Using a combination of several different types of anabolic steroids is a practice commonly referred to as "stacking."