“Research on rough-and-tumble play in animals and humans has shown that it is necessary for the development and maintenance of social awareness, cooperation, fairness, and altruism. Its nature and importance are generally unappreciated, particularly by preschool teachers or anxious parents, who often see normal rough-and-tumble play behaviour such as hitting, diving and wrestling (all done with a smile, between friends who stay friends) not as a state of play, but a state of anarchy that must be controlled.
"Lack of experience with rough-and-tumble play hampers the normal give and take necessary for social mastery, and has been linked to poor control of violent impulses in later life. While studying the young murderers in Texas many years ago, we found an absence of rough-and-tumble play in their early backgrounds when compared to similar nonmurderers we interviewed as controls in our study [among a number of other studies cited].” p89
Neuroscientist Jaak Panksepp proposes a connection between lack of rough-and-tumble play and ADHD. (p100)