Think back to how self-conscious you were as a teenager. I remember staring at my pimply face, frizzy hair, and rapidly changing body, feeling like I would never conform to the beauty standards of the day. I looked around at friend groups, wondering what it would take to be accepted into one of them. I thought that I wasn’t funny enough, or pretty enough, or from the right place to fit in. Being a teenager can feel like you are a purple alien trying to fit into a group of humans.
Why do we all feel this way? Brain science is giving us new answers—and despite what many parents and experts today fear, it’s not social media.
The Primitive Part of Our Brains
The science is this: We have two thought networks. The first, the central executive network (CEN), is responsible for the thoughts we choose to have. When we focus our attention on something, we are using this network.
The second thought network, the default mode network (DMN), is embedded deeper in the brain and is therefore more primitive. Yet often, its thoughts are those we listen to. It constantly harps on us to do more to fit in and tells us that we are not good enough.
The DMN isn’t trying to hurt us; it’s trying to keep us in the clan and therefore safe from danger. But in the process, it often beats us up. Why did I say that stupid thing at the party? Is this outfit ugly? Are they judging me?
A key takeaway from the research literature is that this voice is not you, as in your deepest, truest self. It is an automatic, survival-based system trying to keep you alive, even though its software hasn’t been updated since the caveman days.
The Default Mode Network and the Adolescent Brain
How the thought networks develop from childhood to young adulthood explains why the teenage years are such a sensitive time. In childhood, the two thought networks haven’t wired together yet. Children are not self-conscious or worried about people judging them, because the DMN isn’t running.
The default mode starts coming online in middle childhood and reaches full maturity in adolescence. The central executive network comes online later and doesn’t reach full maturity until the late 20s to early 30s.
During adolescence, we are at the behest of this default mode network, without full support from the CEN to turn it off. For reflective teenagers, this is a total system shock. They look back on how confident, passionate, and self-assured they were as children and wonder what happened. Often, they believe they developed low self-esteem or mental health issues. Not knowing what the DMN is, they take credit for its critical, judgmental thoughts and believe that there is something wrong with them.
Going through this developmental change during the high school years is a perfect storm. The high school environment produces endless “clans” that our teenagers’ DMNs feel they need to fit into to survive. Whether it is being accepted onto a sports team, into advanced math, a friend group, or the invite list to a birthday party, they are constantly presented with potential rejection.
If lots of people in high school are wearing a certain type of clothing or engaging in a certain behavior, it feels to teenagers that the entire world is. And if they don’t fit into those norms, the DMN tells them that they are fundamentally flawed and don’t belong. If you think this is extreme, consider the sobering 2023 statistics on suicidal ideation in adolescents: 27 percent of girls and 41 percent of LGBTQ+ youth report having seriously considered killing themselves.
Taming the Default Mode Network Takes Time
As we get older, we get used to the voice of the DMN. We also rely on past experience to tell us we will be OK. We survived our first romantic break-up, and life went on. The next romantic break-up doesn’t hit as hard. We got fired from our first job, then found a new one we liked better. We learn that we can survive the hard times.
With age, we also get more data points on how there are lots of ways to live. We go out into the world and find our “clans,” which soothes the DMN. During the teenage years, it is all so fresh and new that rejection, hurtful comments, poor performance, and social hiccups hurt that much more deeply.
Why has teenage mental health declined in the past decade? The influences are many. Social media is a crucial factor, as is the rise of real and perceived danger in the world, with teenagers citing climate change, the geopolitical landscape, school shootings, and the pandemic as stressors. Trauma plays a huge role.
Another factor is that with greater awareness comes greater attention and reduced stigmatization. Teenagers who learn about depression, anxiety, suicide ideation, trauma, etc, are more accurately able to identify such experiences in themselves and feel comfortable reporting them in surveys or seeking help in times of need.
No matter what the era, adolescence has always been a precarious time for mental health, and a key driver is that teenagers are listening to their brand-new DMNs, which are telling them that they are not good enough, and too different, to make it in this world. The more we educate teenagers on where this voice is coming from—that it is a primitive, automatic thought network trying to protect us by putting us down—the more power we give them to fight those messages.
We can reassure adolescents that what they are experiencing is normal. They are not weak, or different, or bad—they are experiencing a regular (altogether unpleasant) part of brain development that will get easier in time. Equipping them with knowledge of the DMN—how it behaves, what it sounds like, how to turn it off—can shift their mental health trajectory for life.
