What marijuana really does to your body and brain

Marijuana's official designation as a Schedule 1 drug - something with "no currently accepted medical use" - means it's pretty tough to study.

Yet both a growing body of research and numerous anecdotal reports link cannabis with several health benefits, including pain relief and helping with certain forms of epilepsy. In addition, researchers say there are many other ways marijuana might affect health that they want to better understand.

A massive report released in January helps sum up exactly what we know - and, perhaps more importantly, what we don't know - about the science of weed.