The research, published in international journal Archives of Pediatrics and Adolescent Medicine, polled students aged 13 to 17 in 1999 who were followed up five years later.

• 该项在《儿科与青少年医学档案》国际期刊上发表的调查开始于1999年，调查对象为13岁至17岁的中学生，他们接受了为期五年的跟踪调查。