Mental-health challenges are not unique to competitive student athletes like Isabella, of course: Nearly half of American youths struggle with a mental illness before turning 18, while 12 percent have experienced a bout of depression. But even though playing sports on a regular basis can boost physical and mental health, for some serious high-school athletes—many who train year-round and might need an athletic scholarship to afford college tuition—sports can be a key contributor to depression and anxiety.

“The professional consensus is that the incidence of anxiety and depression among scholastic athletes has increased over the past 10 to 15 years,” says Marshall Mintz, a New Jersey–based sports psychologist who has worked with teenagers for 30 years. As one 2015 study by the National Athletic Trainers’ Association found, “Many student-athletes report higher levels of negative emotional states than non-student-athlete adolescents.” Though parents and coaches are often best positioned to remedy the problem, they also often make it worse.

One reason for this trend is that high-school sports have begun to copy the training methods and intensity levels of college sports. This “sports professionalization” says Timothy Neal, a professor of health and human performance at Concordia University Ann Arbor, is a trickle-down effect of big-time sports, from professional to college and now to high school. More students are specializing in only one sport and playing it beyond one season, sometimes competing on multiple teams throughout the year. The American Academy of Orthopaedic Surgeons found in 2017 that high-school, college, and professional athletes trained in a single sport for a comparable number of months each year. As “intensive parenting” has become the norm, parents in recent decades have pressed upon their kids the idea that endless practice is the route to athletic mastery. Private clubs and teams, which need income year-round to stay in business, have also urged this devotion to one sport.

This professionalization has led to overtraining and exhaustion, which is central to the mental-health problems of competitive high-school athletes. “The biggest problem is sleep loss—all these kids are sleep-deprived,” Mintz says, “and this becomes a major contributor to anxiety and depression.” Long practices and multiple daily workouts mean that athletes have less time than before for other activities, which can amplify the pressures of high school. “Do they need two and a half to three hours of practice?” asks Lonnie Sarnell, a sports psychologist in Millburn, New Jersey, who works with high-school athletes. “That extra hour of practice adds so much stress when you have four hours of homework to deal with.”

Read: The case against high-school sports

All that extra time practicing makes players more vulnerable to injuries, which can be another emotional challenge, especially for those whose identity is closely tied to the sport they play. Some athletes who drop other interests and activities to focus on a sport, and whose self-worth is linked to their performance, can feel lost when they’re sidelined; it’s the rudderless feeling Isabella experienced after tearing her ACL. On top of these strains, teenage athletes have to contend with ordinary frictions that come with being on a team—worries over playing time, making mistakes, and working with difficult coaches. These challenges are only more fraught for players with grand athletic goals.