Beginning at adolescence, kids have what's called a delayed sleep phase, where they start sleep later and sleep later in the morning.
青春期伊始，孩子们会产生所谓的睡眠相位后移症，症状表现为入睡比平时晚，起床也比平时晚。
2
It's particularly surprising to see that a boy's puberty can be delayed as a result of events that happen in adolescence. We've previously assumed that these things are 'locked-in' in early childhood.