When you're young, life should be filled with exuberant play. Sadly, the Centers for Disease Control and Prevention (CDC) says that less than 25% of kids ages 6 to 17 get even 60 minutes of physical activity daily.

That takes a toll on muscles and memory, scholarship and socializing, health and happiness.

And a new study confirms the big impact that lack of physical fitness can have on kids’ mental health.

The study in JAMA Pediatrics looked at data on almost 2 million kids and found that those who were the least fit experienced more anxiety and depression. They also had poorer cardiorespiratory fitness, muscular endurance, and muscular power, which contributed to worse mental health.

That followed a study in the journal Mental Health and Physical Activity that found when 11-year-olds got higher levels of moderate or intense physical activity, they experienced less hyperactivity and behavior problems over the next two years than their more sedentary peers.

It’s little wonder that U.S. kids, who get so little physical activity, contend with a lot of emotional strife. The Department of Health and Human Services says that nearly half of adolescents deal with a mental health disorder, and the CDC found 40% of students feel persistently sad or hopeless.

To promote your children's happiness, help them enjoy daily physical activity. Whether they enroll in school or intermural sports, take long walks, ride a bike, or throw a ball (with you or against a wall), it will make a difference in their todays and tomorrows.