A farmer planting his marijuana crop.
(Image credit: Eric Limon/Shutterstock)

Marijuana is an age-old drug made from parts of the Cannabis plant. It contains the mind-altering chemical tetrahydrocannabinol, or THC. Several countries, and a number of U.S. states, have legalized the drug for medical or recreational purposes. Here's the latest news on marijuana, from how it affects the brain and body, to its potential medical benefits or harms, to possible impacts of legalization.

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