Marijuana
According to the National institute on Drug Abuse (NIDA), marijuana is the most commonly abused illicit drug in the US.
Marijuana is typically smoked; this can be in the form of: 
1) a joint (cigarette like)
2) a blunt (a cigar that has had the tobacco removed and replaced as a tobacco Marijuana combination) this covers the Marijuana’s distinctive odor.
3) a pipe or in a bong/hookah (a water pipe).
When smoked, the main active chemical, THC, is quickly passed from the lungs into the bloodstream and throughout the body to the brain and other organs.
“Not surprisingly, marijuana intoxication can cause distorted perceptions, impaired coordination, difficulty with thinking and problem-solving, and problems with learning and memory. Research has shown that, in chronic users, marijuana's adverse impact on learning and memory can last for days or weeks after the acute effects of the drug wear off.2 As a result, someone who smokes marijuana every day may be functioning at a suboptimal intellectual level all of the time” (NIDA InfoFacts 11/10).
In Lane County, 80.6% of 8th graders report they have never tried Marijuana; that number drops to 54.4% by the 11th grade. When asked how many students hadn’t had any marijuana in the last 30 days 87.8% of 8th graders reported no use, of the 11th grade students 76.3% reported no use in the last 30 days (Student Wellness Survey 2010).
For more information about marijuana, visit the sites below.
Key Links:
Myths and Facts About Marijuana [Parents: The Anti-Drug]
Marijuana: Information for Teens [National Institute on Drug Abuse]