(CNN) As a mom of two daughters, I'm mindful of how girls today have more opportunity than ever. In fact, I tell my girls this all the time: They can be anything they want and shatter any glass ceiling, even the highest one, the presidency.
Be confident and speak up, and you can achieve great things, we tell our girls. You can play any sport, join any after-school club, volunteer for any cause and get the grades. In fact, girls are regularly outperforming boys in school and enrolling in higher numbers in college.
It's a great time to be a girl -- or is it? Because behind all these possibilities is a troubling development: Girls' anxiety and depression are climbing and increasingly turning tragic.
Between 2007 and 2015, the suicide rate for girls between the ages of 15 and 19 doubled, reaching a 40-year high in 2015, according to new data from the National Center for Health Statistics.
"I think no one can dispute the wholesale kind of collapse of girls' wellness right now," said bestselling author Rachel Simmons, who has been working with and doing research on girls for the past two decades.
"It's really a crisis. I don't think I'm overstating it. Everywhere I go, I hear about levels of anxiety that are so crippling that it makes it hard for teachers to teach, and we can't not pay attention to this anymore."
Simmons points to the findings of a 2015 freshman survey by UCLA of 150,000 full-time students at more than 200 colleges and universities.
Twice as many girls as boys reported that they felt depressed frequently or occasionally, and twice as many girls as boys said they were "overwhelmed with all they had to do" -- a 25% jump in the number of girls in both categories in just over 15 years, according to Simmons.
What's behind these concerning numbers? As Simmons writes in her new book, "Enough As She Is: How to Help Girls Move Beyond Impossible Standards of Success to Live Healthy, Happy, and Fulfilling Lives," girls are growing up with outsize expectations of personal and professional success. The pressure to be great at everything is causing them to feel less confident, more fearful of failure and more critical of themselves, Simmons says.
"There is a deep mismatch in terms of what the culture is telling girls and their most vulnerable parts of their psychology," said Simmons, who is also co-founder of the national nonprofit Girls Leadership.
Girls are socialized at a very young age to rely heavily on feedback from others. They grow up paying more and more attention to what other people think of them and whether they are measuring up to those external expectations.
In today's society, that relentless concern about pleasing others is on what Simmons calls a collision course with two cultural changes: the ubiquitousness of social media, which is exacerbating the need to perform, and heightened expectations of what it means to be a successful girl today.
"We're now giving girls access to STEM (science, technology, engineering and math). We're giving girls access to opportunities they've never had before. And we're not doing that and saying, 'Oh, you don't have to have a bikini body anymore. That's cool. You're good. You can look however you want to look,' " Simmons said.
"No, we're saying 'keep your bikini body and become an engineering major and also have a totally lit Snapchat feed on a Saturday night,' and so that's exhausting, and I call that role overload and role conflict."
Social media alone becomes a "virtual second shift" for young girls, almost like a full-time job, as they spend more time on average on Instagram and Snapchat that boys do.
"Social media enables them to curate an exhausting range of identities -- jock, scholar, beauty queen, party girl, best friend, and on and on -- demanded by the new rules of girl success, crammed into a twenty-four-hour day," she writes in "Enough As She Is."
Simmons said she wishes she didn't have to write this book. In her bestseller "The Curse of the Good Girl," published in 2009, she wrote about the need to teach girls how to take up space, find courage and be confident. But in her work with girls on college campuses and elementary, middle and high schools across the country, she started to see that the wellness piece was missing.
"Despite very high levels of achievement, girls were struggling with a sense of imposter syndrome, low lack of confidence, overthinking and an enduring belief that no matter how hard they tried, they were not enough of whatever it was," said Simmons, who has a young daughter of her own.
"Moreover, the terms of success that they had established for themselves were so kind of outsized and unrealistic and unhealthy that they were on this hamster wheel of trying to get something they were never going to get."
Simmons said she has come to realize that in order to help girls become stronger and more confident, we have to attend to their emotional health. "We never thought about girls' leadership as being integrated into their wellness, and ... that's the shift that's taking place, is that we need to start thinking about wellness in tandem with growing their confidence and growing their achievement."
Tara Christie Kinsey, head of school at The Hewitt School, a girls' private school in New York City, and a former dean at Princeton University, said that what she and her colleagues in higher education have seen across college campuses for years are young girls with "amazing ... paper resumes" with all the right grades and SAT scores.
It "looks amazing on paper, and yet the interior life of young women in particular was sorely lacking," said Kinsey, who has a daughter in the third grade and a son in the fifth grade.
She tells the story of meeting with a female college student when her then-5-year-old daughter burst through the office door, so excited to show her mom the contents of her kindergarten folder. When her daughter left, "the young woman looked at me, and she said, 'I remember when I used to have that kind of confidence.' "
As an educator and an advocate for girls and women, Kinsey said, she is focused on the gap between what we know girls need to thrive and be healthy and how we're teaching them every day, whether it's in the classroom or in the home.
"I think that better understanding that gap holds many of the keys to closing yet another gap, the success gap between how girls are faring in school -- where we know they're crushing it, and they're outperforming boys, and they're achieving at levels we've never seen before -- and how they're faring in life after school," Kinsey said. "They're coming up against not only a structural glass ceiling but also a psychological glass ceiling that thwarts their self-actualization."
Kinsey was familiar with Simmons' books and incorporated her research into her work in higher education. When she moved to The Hewitt School, she wanted to bring Simmons' teachings and experience to students, faculty and parents in the community. In 2016, Simmons was named the inaugural Girls' Research Scholar in Residence at Hewitt.
Simmons' work at Hewitt involves helping the girls and young women build their skills in the broad category of emotional intelligence, Kinsey said, with a focus on healthy risk-taking, conflict resolution, self-advocacy, managing friendships, and the giving and receiving of feedback.
She may be sprawled on the floor with an entire grade of middle-schoolers, tracing their bodies for an exercise on the difference between feelings you sometimes keep inside, such as jealousy, and feelings you express, such as anger. She might be sitting crisscross apple sauce with elementary school girls, talking about the difference between a real apology and a not-so-real apology.
Or she may be standing on a chair and reciting a poem demonstrating how the pressure to be perfect really undermines the ability to give and receive authentic feedback.
"What I'm trying to do is fill in the blanks in terms of some of the skills that they don't have," Simmons said. "So, sure, they're really good at doing their worksheets and the homework and sitting quietly in class discussions and taking exams, but when something goes off the rails, then we're working with them on, how do you cope? We're filling in the blanks, and I contend that if you fill in the blanks ... then we're going to see a better balance between all of this ... on-paper success and what's happening inside.
"But right now, things are out of whack. We got overdeveloped on paper and very underdeveloped in life and in terms of resilience (and) adaptability."
It is that fear of failure that can really be crippling for girls and young women today, which is why Simmons, who is also a leadership development specialist at Smith College, regularly concludes her orientation programs on college campuses with a graduation ceremony. The young women who attend will each receive a "Certificate of Failure."
The mock diploma reads, "Having honorably fulfilled all the requirements imposed by the overload of high school, you are hereby certified to screw up, bomb or otherwise fail" during college "and still be a totally worthy, utterly excellent human," Simmons writes in her book.
The girls laugh, she writes, but then they take those certificates back to their dorm rooms. "Every girls needs a Certificate of Failure," she writes.
At Hewitt, Simmons also works with the teachers, helping them see the importance of trying to teach soft skills such as resilience and adaptability just like they are teaching anything else.
Instead of giving feedback on written work, a teacher might do a one-on-one consultation with the student in which they focus on her goals and what she hopes to achieve in her next writing sample.
In math, teachers don't typically give girls grades on quizzes; they give written feedback so the girls can learn from their mistakes.
"You see how that's just completely transformative to girls and relationships, to their own achievement," Kinsey said. "It's not about grades. It's about growth. It's about feedback. It's about failure. It's about honoring mistakes as a necessary part of the learning process."
As part of her work at Hewitt, Simmons also meets regularly with parents and tries to help them "combat the sense of shame and 'not-enoughness' that so many parents have."
"This is an era in which parents are probably the least confident they're ever been in themselves," Simmons said. "If we want our kids to feel like they are enough, the parents have to feel like they are enough."
During coffee talks, she tries to help parents feel comfortable enough to share what they are most afraid of, such as concerns that their daughter doesn't have a ton of friends or isn't getting the best grades.
"We had a couple of faculty members who aren't parents who were sitting there going, 'Oh, my God. I had no idea that parents were that scared about their kids, and all I see is 'my daughter didn't get a good grade on the test,' and that anger is actually fear,'" Kinsey said. "That anger is fear, and what Rachel is doing in such a beautiful way is saying ''if you don't get in touch with that, you're not really modeling for girls what they need.' "
Muffy Flouret, who has a daughter in the seventh grade at Hewitt, said Simmons is helping students and parents understand what it means to fail and how to bounce back.
"She's on the edge of the research of how do we raise girls in the community, and it's invaluable, because parents who might not think twice about saying, 'Well, you didn't get the A. I'm not so happy about that,' might now think twice about that reaction," Flouret said.
She also said Simmons is helping the community understand the perils of trying to be the best at everything.
"To create this sort of pressure that you have to be the top of the soccer team and you have to be top of the debate team, it's not sustainable, and it's not realistic," she said. "Where does that leave you as an adult? You have to be able to bounce back and react to things."
Jo-Anne Williams, co-chairwoman of the Hewitt Parents' Association, who has a daughter in the seventh grade at the school, attends nearly every one of Simmons' events with parents.
"It really causes you to take a step back and say, 'What am I really doing? Am I just trying to create a cookie cutter of myself, or (what) I want her to be?' " Williams said. "I worked in finance. I was always strong in certain subjects that she doesn't happen to like all that much. Am I pressuring her too much on math because that's not her thing? She's a dancer. She's a great writer. She's other things."
Williams said her daughter recently told her mother that she chews her fingernails because she's a perfectionist.
"I said, 'Well, I used to chew my fingernails when I was a kid,' and I said, 'I stopped doing it. And I also used to be a perfectionist and I've stopped doing that, so there's hope for you.' "