Eric Wargo, NIDA Science Writer
March 26 2013

“Marijuana is natural, so how can it be harmful?”

Lots of teens ask us this question, and it’s a good one.

People often think that substances found in nature are automatically safer than chemicals that are made in a laboratory or a factory. It’s not that simple, unfortunately. Lots of beneficial substances are human made (medicines, for example), and lots of harmful ones come straight from the earth.

A brief history of tobacco

Tobacco is a great example. Like marijuana, tobacco is a plant whose leaves have been dried, crumbled, and smoked for thousands of years. It was used in religious rituals by Native Americans, who believed that exhaling tobacco smoke carried their thoughts and prayers to heaven; they also believed it possessed medicinal properties.

Once American settlers began growing the crop and exporting it to Europe and the rest of the world, tobacco enjoyed a reputation kind of like marijuana does today: Some monarchs and religious leaders thought it was unhealthy and morally corrupt and tried to ban it; but lots of people enjoyed the “precious weed” and sided with the physicians of the time, who actually praised its healing virtues—claiming that smoking tobacco could cure most forms of sickness and even protect a person from getting the plague!

It wasn’t until around the 1950s that modern medicine, armed with better science, established the truth about smoking tobacco—it can cause diseases like lung cancer and it is highly addictive. No one would now argue that tobacco is safe, let alone good for you. But it is “natural.”

Natural does not equal safe

Marketers of foods and other products use the “natural equals good for you” assumption all the time to manipulate people’s buying behavior. For instance, when shoppers see the “All Natural” label on a food, they tend to think it’s good for them even if it contains lots of unhealthy sugar or fat—both of which are, like tobacco, “natural.”

We still don’t know whether smoking marijuana causes lung cancer like tobacco does, but strong evidence shows that it does other bad stuff: It interferes with thinking and memory, it can lower your IQ if you smoke it regularly in your teen years, and—as a result of these and other things—it can set you up to miss achieving your full potential in life.

Is a “natural” way to hurt your brain any better than an unnatural one?

Eric Wargo is a science writer at NIDA. Before coming to NIDA, he wrote for an association of psychological scientists, people who study all aspects of the mind and human behavior. He is excited to work at NIDA, because NIDA scientists study the brain, and the brain is at the root of everything we humans do.

-->