It controls every thought, emotion, breath and every single process that regulates our bodies.
It, or the brain, is going through a significant amount of change during teenage years. Imaging studies of the brain and its development display a kind of ‘cleaning up’ from the back of the brain to the forward part of the brain. The forward part of the brain is involved with executive functioning — the process of being able to slow down, make decisions and think through them, not reacting impulsively, staying organized and being able to make complex decisions. Joanna Quigley, a child and adolescent psychiatrist at the University of Michigan (UofM), believes that there are significant physical changes that take place during the teenage years, impacting the connections within the brain.

“Your brain is literally growing up during your teenage years, so those areas of the brain are connecting more efficiently,” Quigley said. “That’s why some kids might struggle with consequences of behaviors or decision making.”

Amidst growing up and the changes that teenage brains undergo, there are a multitude of stressors that impact teenagers, like socioeconomic and environmental factors.

“There may be more exposure to bullying or other stressors,” Quigley said. “It’s all a big soup of change that happens at the same time and some of it is physical in your brain and some of it is environmental.”

Similarly, Christopher Monk, a professor of the Department of Psychology and Department of Psychiatry at (UofM), specializes in adolescent brain development and how their development differs from adults. Monk says that the symptoms of psychopathology — the study of mental illnesses and disorders — stems from adolescence.

“To reduce mental health disorders, it’s important to start looking at adolescents,” Monk said. “As well as trying to understand how to prevent mental disorders in the first place.”

On one hand, Monk shares that anxiety can emerge in childhood, but becomes prevalent during adolescence. On the other, depression is not as present in children — depression starts to surface in adolescence or young adulthood. Part of this is due to the fact that brain connections are made quite early during the brain’s development, even prenatally. Humans are born with thousands of synaptic connections, where neurons connect to communicate with one another.

Monk notes that babies create more connections, compared to adults, before they get ‘pruned away’ as too many connections prove to be overwhelming.

“You’re born with all these connections, but they’re really weak connections,” Monk said. “It’s really up to the environment to sculpt them, and figure out what connections are going to get stronger and what connections are going to get weaker. You don’t want all those connections, that actually would not be a good thing, in terms of processing information.”

The most important connections are the connections that you’re going to maintain for the rest of your life, Monk says. During infancy, that is the time when the brain can learn multiple different languages. This is because the brain is much more moldable, being able to differentiate sounds, whereas the adult brain is much more fixed.

“Your brain is a sponge and can just acquire all this knowledge,” Monk said. “Adults lose that ability to absorb our culture and the environment.”

Another significant factor in determining how the brain creates connections is dictated by genetics and “what’s going to be wired and what will be forgotten,” but it is arduous to identify what genetic markers impact connections, as there are a myriad of genes that increase susceptibility for having a condition.  “When we’re looking at most mental health conditions, particularly something like anxiety and depression, it is very complicated in terms of what genes may relate to it,” Monk said. “But the idea is that certainly, genes and the environment are interacting with one another to increase the risk for depression.”
That being said, each brain is different and Monk discloses that some individuals who have experienced hardships may be fine, but others who have experienced something similar may have a mental health condition.

“There are just individual differences of brain connections and it’s just because of that person’s response, both genetically and environmentally, that their brain is the way it is,” Monk said. “It has adapted to their environment as best it can be.”

Monk’s research focused on trying to understand from a physiological perspective why some brains may be more susceptible to depression or anxiety, wondering what factors impact the adolescents’ brains and their development and connections. Monk’s research focuses specifically on children growing up in low income backgrounds. To understand how stressors impacted their brain connections, brain imaging and assessment of their mental health was conducted, beginning when they were 15 years old and continuing to now, when they are in their early to mid twenties.

“Sadly, many of these now young adults were exposed to violence, experienced marital hardships and neglect,” Monk said. “But at the same time, there’s a lot of great things going on with these families as well.”

The challenges that Dr. Monk documented, such as violence exposure, were examined and were shown to alter brain activation, connections and myelination in the brain, all at 15 years old. But Monk feels that these complex experiences altered the network connectivity across the brain, not impaired.
“We’re not talking like neurological impairments; we see alterations in the brain due to these challenging situations and our interpretation of this is how the brain is changing in response to those situations,” Monk said. “It’s not like it’s good or bad, it’s just adapting to these environments.”

Childhood experiences and the impacts of those environments will influence the connections of the brain and how people live their lives. In addition to childhood experiences, age impacts the efficiency of connections because of the presence of myelin, a fatty sheath that covers axons, a part of the nerve cell which carries electrical impulses. These axons fire ‘action potentials,’ allowing the brain to communicate with different areas of the brain. Although crucial for fast connections between different areas of the brain, humans are born with relatively little myelin; throughout the first 20-25 years of life, humans develop more and more myeloma. Monk shares that this was surprising to find, as this indicates adolescents have less myelin than adults. But this is a double edged sword. For adolescents, myelin allows for more rapid communication between different areas of the brain. For young adults, they may have faster communication than an adolescent, but at the same time, they have more myelin covering, meaning there’s less plasticity, less flexibility in the brain, and less ability to learn new information.

“They process existing information really well, but have less ability to make new connections,” Monk said.

This development is not only restricted to mental cognition; athletic areas grow just as fast during adolescence, as teenagers learn new skills and improve their athletic capabilities.

“You have this nice balance from a neurological perspective in terms of being open to learning information, being coachable and being able to adapt, but also being incredibly fast,” Monk said.

Adolescence is the prime time for new experiences and learning, and some of those new areas of exploration include substance use. There’s new research coming to the surface about the impact of substance use in teenagers and its impact on brain connections; in Michigan, as well as other places throughout the United States, cannabis has been legalized and is more prevalent. The Adolescent Brain Cognitive Development study, partly conducted at the University of Michigan in addition with a handful of other institutions across the country, are conducting brain imaging on thousands of kids, starting at age 10 and following them into adulthood.

“We will be focusing on the relationships among childhood experiences, brain maturation and mental health and how these influence one another over time,” said Dr. Mary Heitzeg, a leader of the study on their website.

The primary focuses are identifying factors that impact one’s environment: family, friends, their neighborhood etc. These aspects help shape lives and their connections within the brain, resulting in harmful or beneficial outcomes. With the focus of modern adolescents’ brains and their connection, Monk observes that Gen Z is much more open and accepting of individual differences in regards to mental health. This is exceptionally different compared to previous generations, when the norm was to conceal and deny hardships one experiences, Monk says.

Today, in addition to unique environmental factors that impact individuals, there are other factors — such as technology and economic stressors — which contribute to the “mental health crisis.” Specifically, the influx of iPhones and the relevance that social media holds in society today is a major aspect in many teenagers’ lives today.

“But it is a real potential risk,” Monk said. “Things like cyber bullying, fear, missing out on something and just constantly being on your phone, always trying to have to curate whatever on social media, it’s a constant stress.”

Monk declares that there are potential ties with mental disorders and social media focused interaction: “You can stay in on Friday night because you can just talk to your friends through social media, rather than going out and then maybe something is lost and that could somewhat result in depression and anxiety,” Monk said.

Beyond the surge of technology, economic stress is another crucial factor worth noting; Monk shares that there seems to be an assumption that a growing number of individuals, particularly among the millennial and Generation Z demographics, will not be as economically successful as their parents, casting a cloud of anxiety.

“An assumption until recently in the United States is that offspring, in general, would do better economically,” Monk said. “Now, things are less and less secure. I think that increases anxiety and fear a lot.”

Undoubtedly, COVID-19 led to an increase in anxiety and depression, as well as eating disorders, Monk shares. This is consistent with a study conducted by three doctors at UCLA — Denise Chavira, Carolyn Ponting and Giovanni Ramos — who found that 17% of youth had a probable mental health disorder in July 2020 compared to 11% in 2017. Monk believes that being home for that extended period of time is one of the primary reasons why anxiety and depression rates increased.

“Being at home all the time can be a real stressor for everyone and people get on each other’s nerves and worse,” Monk said. “That was certainly the early signs that it contributed to worsening mental health in young people.”

Needless to say, stressors can significantly impact teenage brain connections; Quigley, who works with kids with a variety of different mental health care needs, believes there’s a possibility to work preventively. To Quigley, getting treatment during adolescence for a mental condition leads to healthier brain development. Moreover, it can reduce the risk of a mental illness being severe in adulthood and better equip those with a disorder with the skills to manage it.

“If you get cared for now, you’ll have better outcomes as a grown up,” Quigley said. “All this change going on in your brain can have a really big impact over time.”

The brain makes connections on the level of the cells in the brain: neuron and glial cells. There are also different types of neurotransmitters that are released and used by the cells, and it is through those connections between the cells, which are part of bigger pathways in the brain, that connections are made between different parts of the brain. An example of this is serotonin, a neurotransmitter that is responsible for happiness.

“Serotonin is a molecule that has actions on different types of cells,” Quiqley said. “When the cells interact with serotonin, it can then trigger other processes in that cell or other pathways to get activated.”

Quigley feels that these areas are most likely less developed during the teenage years in part of being able to embrace independence and have risk-taking tolerance, which may look like leaving the home you grew up in.

“Those risks go way, way back, like to go out and hunt on your own, gather on your own, do those things on your own, feeling comfortable trying new things,” Quigley said. “There was a role for it, but we live in a world where we’re dealing with really complex levels of decisions.”

Quigley shares that one of the challenges of studying the brain lies in the fact that “we can’t break your head open and look at it.” As a result, brain researchers rely on MRIs and complex psychological tests to get a glimpse under the hood and hopefully better understand one’s emotions, behavior and personality. Currently, people who have higher use of technology and social media are being studied, wondering how they are doing in terms of their emotional health and in their ability to make decisions.

“We’ve been able to look at that by how long you spend on certain platforms, and it looks like kids who spend more than a certain amount of time might struggle more,” Quigley said.

There are similarities across teenagers and their brain connections, especially when teenagers are going through a period of self improvement as well as questioning their identity — they tend to deal with pretty strong emotions that can feel like all-or-nothing.

“All these things are going on at one time and that’s pretty universal for all teenagers,” Quigley said. “How likely someone is to be impulsive or how likely someone is to worry more or be vulnerable for depression, all those things are different on a person to person basis.”

During these times, the different parts of the brain are still communicating with each other, it’s just not as efficient.

“The parts of your brain that deal with emotion, and even risk taking, are working pretty well and then the connections to that part of your brain then helps you slow down and put the brakes on decisions,” Quigley said. “Those connections are still developing, they’re just not talking as well to each other, so you don’t slow down.”

Stress and trauma can have a big impact on the brain and its connections, a sentiment shared by Monk and Quigley, but substance use is another determining factor.

“That’s why, as doctors, we get worried about alcohol use and cannabis use and any substance use during this time of your brain growth,” Quigley said. “There are changes or probably impacts of dealing with serious depression or really, really bad anxiety, which is why it’s so important to be getting treatment for those.”