Before we discuss marijuana drug testing and the types of marijuana drug tests available, let's examine the drug that is being tested in this case and the types and scale of its use in the United States.

Marijuana comes from the cannabis plant. The major psychoactive chemical compound in cannabis is delta-9-tetrahydrocannabinol (usually abbreviated as THC). At least 66 other cannabinoids are also present in cannabis. The most common form of cannabis is the dried, herbal type.

Recent trends in teen marijuana use have been promising, however there are still many users in the teen age group. For instance, past-year use has fallen by 24 percent among 8th-graders, 23 percent among 10th-graders, and 15 percent among 12th-graders since 2001. Perceived availability of marijuana fell significantly among 10th-graders, from 72.6 percent in 2005 to 70.7 percent in 2006. (Learn more statistics over at the National Institute on Drug Abuse's Marijuana Facts for Parents page!)

Some of the signs of marijuana use that can be qualitatively confirmed by a marijuana drug test include bloodshot eyes, dizziness, silliness, and difficulty recalling recent events. If you see these symptoms, you may want to try a saliva drug test for marijuana, as it can tell you whether someone is currently high.

A marijuana urine test is also a popular type of marijuana drug test. Within hours of use, marijuana can be detected in urine and will remain detectable in urine for up to 3-10 days after use, possibly longer (even 15-30 days after use) depending on frequency of use, body weight, and other factors. A marijuana urine test is very easy to perform and 98% accurate. You can also buy a home drug test that will test not only for marijuana but for other commonly abused drugs.

The final marijuana drug test we will discuss is the hair drug test. This test is unique, because it can give you a 90 day history of a person's drug use. If you take a 90-120 strand lock of hair from the root of the subject's head, you will for each half inch in length of hair learn about 30 days of drug history. Although it takes 5 days to a week after use for marijuana to work its way into the hair follicle, once it is there it will stay there.

National Institute on Drug Abuse (U.S. Government information on marijuana and other drugs)

SAMHSA (Substance Abuse and Mental Health Services Administration

Office of National Drug Control Policy

National Institute on Drug Abuse for Teens A resource specifically designed for teenagers.