Updated February 07, 2013.

Marijuana is the illegal drug most often used in this country. Since 1991, lifetime marijuana use has almost doubled among 8th- and 10th-grade students, and increased by a third among high school seniors.

These questions compiled by the National Institute on Drug Abuse are the most asked by parents concerning marijuana.

• What is marijuana? Aren't there different kinds?
  
  What are the current slang terms for marijuana?
  
  How is marijuana used?
  
  How many people smoke marijuana? At what age do children generally start?
  
  How can I tell if my child has been using marijuana?
  
  Why do young people use marijuana?
  
  Does using marijuana lead to other drugs?
  
  What are the effects of marijuana?
  
  What happens after a person smokes marijuana?
  
  How long does marijuana stay in the user's body?
  
  Can a user have a bad reaction?
  
  How is marijuana harmful?
  
  How does marijuana affect driving?
  
  What are the long-term effects of marijuana?
  
  What about pregnancy: Will smoking marijuana hurt the baby?
  
  What happens if a nursing mother uses marijuana?
  
  How does marijuana affect the brain?
  
  Can marijuana cause mental illness?
  
  Do marijuana users lose their motivation?
  
  Can a person become addicted to marijuana?
  
  What is "tolerance" for marijuana?
  
  Are there treatments to help marijuana users?
  
  Can marijuana be used as medicine?
  
  How can I prevent my child from getting involved with marijuana?