A single concussion experienced by a child or teenager may have lasting repercussions on mental health and intellectual and physical functioning throughout adulthood, and multiple head injuries increase the risks of later problems, according to one of the largest, most elaborate studies to date of the impacts of head trauma on the young.

You cannot be an athlete, parent of an athlete, sports fan or reader of this newspaper and not be aware that concussions appear to be both more common — and more dangerous — than most of us once thought. According to a report released last week by the health insurer Blue Cross Blue Shield, based on data from medical claims nationwide, the incidence of diagnosed concussions among people under the age of 20 climbed 71 percent between 2010 and 2015. The rates rose most steeply among girls, with the incidence soaring by 119 percent during that time, although almost twice as many concussions over all were diagnosed in boys.

The report acknowledges that the startling increase may partly reflect a growing awareness of the injury among parents, sports officials and physicians, which has led to more diagnoses. But the sheer numbers also suggest that more young people, particularly young athletes, are experiencing head injuries than in the past.

Similar increases have been noted among young people in other nations.

But the consequences, if any, for their health during adulthood have largely remained unknown.