What’s the harm in a little beer? That’s usually how it starts. Teenagers often are tempted to try some alcohol. Many give in when they are just 12 to 16 years old. Although they know they should avoid alcohol, many don’t. Some will soon end up drinking a lot — and often. This is called binge drinking. And when it begins at a young age, it can have lasting impacts. That’s the conclusion of a new study in rats.