A large study published in May in the journal Pediatrics looked at a group of 8,327 children born in Hong Kong in April and May of 1997, for whom a great deal of health data has been collected. The researchers had access to the childrens health records, showing how their doctors had documented their physical maturity, according to what are known as the Tanner stages, for the standardized pediatric index of sexual maturation. What we found was the girls who had earlier breast development had a higher risk of depressive symptoms, or more depressive symptoms, said Dr. C. Mary Schooling, an epidemiologist who is a professor at the City University of New York School of Public Health, and was the senior author on the study. We didnt see the same thing for boys. Earlier onset of breast development in girls was associated with a higher risk of depression in early adolescence even after controlling for many other factors, including socioeconomic status, weight or parents marital status. Other studies, including in the United States, have shown this same pattern, with girls who begin developing earlier than their peers vulnerable to depression in adolescence. Some studies have found this in boys, though its not as clear. But there is concern that girls whose development starts earlier than their peers are at risk in a number of ways, and across different cultural backgrounds.