Depression is a common disorder among children (less than 18 years). Approximately 5% of children at any one time may suffer from serious depression. The prevalence of depression increases with age, especially after the onset of puberty. There is no gender-related difference in the prevalence of depression among pre-adolescent children. However, onset of puberty is associated with a marked increase in the rate of depression among females, with a female to male ratio of 2:1.
John Bennett ¸University of Michigan
While some researchers have suggested that hormonal changes may be the cause of the sudden rise in depression among young women, others have found that measurable hormonal changes have no direct correlation with depression in adolescents. Gender differences in attitudes toward secondary sex characteristics, do correlate with depression, though it’s hard to know if the differences in attitudes are a cause of depression or an effect (or both) IQ correlates with depression in girls. (Smart girls are more likely to become depressed.) In boys the correlation is inverse (stupid boys get depressed more often)

Why is puberty such a depressing time for young women? Could it be the increasing emphasis on appearance?

Girls usually begin puberty approximately two years before boys. Therefore, they experience the dramatic bodily changes that secondary sex characteristics bring, such as breast development and weight gain, while boys’ bodies stay the same for a couple more years. Girls tend to dislike the physical changes in their bodies, especially the weight gain that makes their bodies curvier. However, boys tend to like their physical changes once puberty hits (Nolen-Hoeksema, 1990).
The pressure to cease being a tomboy? So, what is it?: the transformation from a fairy princess in to a potential liability, an object whose chastity must be guarded? Could it be the fact that until puberty girls are pretty much as strong and as fast as boys and just as fierce at winning at tag or dodgeball?

There is no accepted reason for the higher rates of depression among women, or the puberty correlation—

Another study showed that a mother's depression may cause her daughter to hit puberty earlier (Journal of the Society for Research in Child Development: Bruce J. Ellis, PhD, of the University of Canterbury in Christchurch, New Zealand and Judy Garber, PhD, of Vanderbilt University in Nashville) Is the daughter rushing to join her mother in the sadness of womanhood?