One in two American children will develop a mood or behavioral disorder or substance abuse addiction before age 18.


When I read this statistic in Katherine Reynolds Lewis’ new book, “The Good News about Bad Behavior,” my reaction was: Wait, what?


I have been hearing anecdotally for years about an epidemic of anxiety, depression and substance abuse among kids, but could it really be this widespread?


Lewis had the same reaction when she found the government data by the National Institute of Mental Health that looked at more than 10,000 children.


“I was so shocked,” she said. “Why was this not on the front page of every newspaper?”


A veteran journalist, she dug into the study, reported it out and found the only people who aren’t surprised by the research are high school guidance counselors and mental health professionals — the ones on the front lines of this crisis. In fact, 32 percent of children have an anxiety diagnosis, she said.


Lewis builds a convincing case with a substantial amount of research that we are seeing an actual change in children, not just a rise in diagnosis. This is coupled with a documented rise in misbehaving, undisciplined children, she writes.


“Children today are fundamentally different from past generations,” she writes. “They truly have less self-control.” Her book explores why and what to do about it.


As a parent, it’s a relief to hear this confirmed. Many of us had the suspicion that our children and their peers were growing up fundamentally different than we did. Lewis explains why this might be: We had a lot more independence, more responsibility around the house, more unstructured time and free play. We could take more risks, had to learn to manage our own time and work out our own conflicts at a younger age. All of this helped us practice and learn self-regulation.


The other massive sea change is the explosion of media in all aspects of kids’ lives, bombarding them from ever-younger ages and for longer hours. The messages they often get from being immersed in social media: You are not good enough, and everyone else is having a better life. No wonder we are seeing skyrocketing anxiety in younger generations.


“We have to recognize that our kids need so much more support to manage their behavior and emotions than we did when we were growing up,” she says.


The parenting techniques our parents used will not work on our children because they are growing up in such a different way. That’s not to say our parents were wrong, Lewis said. We just need new parenting tools to cope with how modern childhood has changed.


She makes a radical argument: Traditional punishments and rewards simply do not work to raise capable children. These techniques are not helpful long-term and only create extrinsic motivation rather than building intrinsic motivation. Instead, we need better connections with our children, smarter consequences and more consistent boundaries with them.


So, how do we do this? It can be confounding, especially for those of us raised with a very different parenting style of strict rules and the fear of breaking them. Lewis says to begin with managing our own response before we respond to a child’s misbehavior. Even 10 seconds of breathing will calm our physiology, and children mimic our heart rate and breathing. We can either help them calm down or ramp them up even more, she said.


Then, find some small way to connect before you talk about the problem. Use a language of respect and mutual agreement. Set and enforce limits, and be willing to live with the natural consequences if those limits are ignored, she said.


Lewis has been a parent educator for years and is raising an 11- and 14-year-old, along with having helped raise a 25-year-old stepdaughter. Her tween and teen are allowed 30 minutes of screen time per day during the week, after they finish their homework, household chores and music or sports practice. No screens are allowed in the bedrooms. Cellphones and devices are turned in no later than 8:30 p.m. If they need their phone while doing their homework, an adult is nearby to help keep them on task.


“I’m looking forward to when they can self-regulate that,” she laughed.


I was amazed to hear how she and her husband have managed to set and enforce such limits without constant nagging, yelling and battles.


Ultimately, the challenging message she shares with parents is a hopeful one.