NIDA scientists are always saying that teens shouldn’t use drugs, tobacco, or alcohol. But do you know why they say that? Because of scientific studies like this one by Dr. Jay Giedd, which shows that your brain won’t reach its adult potential until you’re over 20 years old. If you’re a teen—even if you’re a high school senior—your brain is still maturing. Your neurons are still developing, and connections between different parts of your brain are still forming. Drugs and alcohol may mess up that process.
Along with his colleagues at the National Institute of Mental Health, Dr. Giedd created this scientific figure.
This picture is a cartoon depicting how the human brain continues to change between the ages of 4 and 21 years. As you move from left to right along the red arrow, the brain gets older. Above the arrow are side views of the brain (as if someone was standing in front of you, looking toward your right shoulder). Below the arrow are views of the brain from the top (like you are looking down on someone’s head).
So what’s with the rainbow colors? The colors represent the amount of “gray matter” (or active brain cells called neurons) that the researchers found in brains of different ages, using a brain imaging technique called MRI. Gray matter isn’t usually this colorful (hence the term ‘gray’ matter), but these brain pictures have been color-coded to show areas of more or less gray matter. Pink and red areas have the most gray matter, while green and blue areas have the least.
So, who do you think has more gray matter—you, or your parents? What does the figure show?
Yep—you do! It turns out that the number of neurons in your brain actually decreases as you get older. Younger brains have more gray matter (represented by the pink and red areas) than older brains (which are more green and blue). But wait—if the number of neurons in your brain is going down as you age, does that mean you’re getting dumber?
Fortunately, no. The total number of neurons in your brain isn’t as important as how your neurons connect to each other. As you get older, everything you learn and experience shapes the connections between the neurons in your brain. Over time, the connections between neurons become stronger. Your brain also develops more myelin—a white substance that wraps around neurons, insulates them, and helps them communicate more effectively. It’s like starting with a blob of clay and carving it away to make a sculpture: eventually you get a sleek, smart, mature adult brain, like the blue brains on the far right of the figure.
This figure also shows which parts of the brain mature first and which mature last. One of the very last areas to develop is the prefrontal cortex—the part of the brain located just behind your forehead. This part of the brain is responsible for helping you make good decisions, and isn’t fully mature until well after you graduate from high school! Scientists think this might help explain why teens tend to take more risks than adults, including experimenting with drugs.
Does all this mean that teens can’t make smart decisions? No. Teens can and do make good choices all the time. What this figure shows is that your brain doesn’t reach its full potential until you are in your mid-twenties. Basically, teenagers have a lot of brainpower still to come online—good reason to avoid stunting your potential brain power now with drugs or alcohol.
Watch some cool time-lapse movies showing how the brain changes with age.