(CNN) -- My teenage years, like many of our teenage years, were raw ones. I felt vulnerable, destabilized and confused, and I chronicled every bit of it on the pages of highly guarded diaries.

Looking back, I see there was a beauty to this rawness. All those strong feelings helped me figure out who I was and what kind of people I wanted around me. I also feel lucky to be a part of the last generation to experience childhood without much in the way of digital life, and the last to be influenced by Gen X slackers rather than the self-optimizers who came next. This rawness was somewhat protected from societal influences telling me I should do and be more.

That's not true today. Girls are growing with a rising number of external pressures, making their transition into teen and adulthood far more psychologically disturbing than it used to be. Research shows sharp spikes in depression and anxiety among girls in recent years, at rates notably higher than boys.

In her new book, "Girls on the Brink: Helping Our Daughters Thrive in an Era of Increased Anxiety, Depression, and Social Media," Donna Jackson Nakazawa looks into why this is the case, and what we can do about it. CNN spoke with Nakazawa about new brain science on girls and puberty, and how our fast-paced, online lifestyle doesn't work well with our psychological needs.

This interview has been edited and condensed for clarity.

CNN: What is it about this moment in time that makes life so much more emotionally challenging for teenage girls?

Donna Jackson Nakazawa: There is so much focus on performance and competition. Our children are missing that important part of childhood, those in between years, ages 7 to 13, when they should be doing things like hanging out with their friends and lying in the grass to chat about whatever. We've replaced that with a fast-moving culture and have also added in social media, which kids are not supposed to be on until age 13, but many get on much earlier.

Once they are on social media, the focus on appearance hits girls especially. They are more likely to be "liked" or "disliked" based on their looks, and sexualized, than boys. They learn that the more clothes you take off, the more "likes" you get, and that their bodies are going to get evaluated.

Add to this the threats of global warming, school shootings and everything else. It's all heating up, literally, and social media platforms are created to increase the intensity of emotion. And then we have to layer upon that the stark reality that girls routinely face added threats like sexual harassment, rape and violence against women by virtue of being female.

CNN: And girls' brains are particularly sensitive to these stressors?

Nakazawa: Puberty is a super vulnerable time for girls' brain development. Of course, this is true for boys and everyone on the spectrum, too, but it is especially true for girls. When estrogen comes on board during puberty, it is particularly powerful at increasing a potent stress response to unmitigated stressors, and there is good reason for that.

Estrogen, evolutionarily speaking, is a very groovy hormone and master regulator in the brain. On the good side, in normal circumstances, it gives women this added immune response that helps keep them healthy and strong. But when a woman faces big ongoing stressors in the environment, it can make our systems overreact. This is why women have a more robust response to vaccines, and why women suffer from autoimmune diseases at many times the rate of men. Social stressors can evoke an immune response similar to that of experiencing physical harm.

When girls experience overwhelming social and emotional stressors at the same time that estrogen is coming onboard during puberty, this can exacerbate the ill effects of stress on health and development.

CNN: On top of all that, girls are going through puberty at younger ages.

Nakazawa: Puberty is happening earlier at a time when the brain isn't supposed to be remodeled. All those parts of the brain that help discern what we should respond to and what we shouldn't, and when we need help, haven't fired up yet.

Scientists are still trying to parse out why puberty is happening earlier, but we do know that it is happening. Back in 1800, girls got their periods around age 16; in the 1900s, it was around age 15; and in 2020, the average age was 11. It might be that development is sped up by stress or a shift in diet. Some neuroscientists posit that it is possible that the sexualization of girls at an early age is perhaps another part of the reason why they are going through puberty early. If the environment is telling you you are sexual, then it might trigger the pathways that trigger puberty. But for each of these theories there is always someone who says we don't know.

Whatever the reason, more and more girls are going through puberty younger, which means they are having feelings and experiencing increased stress before their brains are fired and wired up to handle it. This is an evolutionary mismatch.

CNN: Puberty, for everyone, tends to be a time of strong feelings and some level of alienation. How can you tell the difference between typical moody teens and a mental health disorder?

Nakazawa: The classic sign is that your child is no longer talking to you or anyone. They are isolating, irritable, picking fights with friends, sleeping all the time or not sleeping at all, and experiencing persistent sadness, hopelessness and fatigue.

This is why, when your daughter comes to you with hard things, try to make it a good experience for her. If a child says they can talk to their parents about anything, that says a lot about how the child is doing. Parents need to try to find ways to keep the conversation open, and not just with them, but with anyone, whether a favorite aunt or teacher.

CNN: Still, the solution to this problem isn't something parents can or should handle on their own, right?

Nakazawa: There are so many different ways to bring in the wider community. Too many parents think they are alone in dealing with this, but we are not alone, and we shouldn't be thinking this is all on us. There is going to be a time when our kids aren't talking to us, and it is OK to reach out to the school and say you need help. You are not a failure if your child is anxious or depressed, and you can't handle it on your own. Why should we think we are the only ones with viable advice?

Talk therapy can help; there is very good evidence. So can having a wider community, which can provide a lot of reassurance for kids — because that is how humans evolved across evolutionary time — we knew that the tribe had our back. We came from communal settings, but today there is so much isolation, and kids feel as though they are competing against each other, which makes them less likely to feel connected.

When you get the community involved, your kids get a sense from the wider world that they matter and that there are other adults in the world that say, "I see you over there." We want to get our kids involved in community-wide events that are not about performance or evaluation, or about external validation, or building up their resume. Instead, we want these experiences to help them know they matter because they matter and build up their intrinsic worth.

Overall, the more we make the wider world seem compelling, inviting and exciting to our girls, full of healthy connection and different from their online social media world, the more our girls feel safe.

When they feel safe, the stress machinery in their brains is less likely to get engaged, and they have a better chance at getting through their teen years without depression or anxiety. Girls' brains at puberty are incredibly agile; they are taking a lot of social cues at once. If these cues are good and we eliminate a lot of the stressors, the adolescent female brain is a superpower.

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