Before adolescence, the rate of depression is about the same in girls and boys. However, with the onset of puberty, a girl's risk of developing depression increases dramatically to twice that of boys.
Some experts believe that the increased chance of depression in women may be related to changes in hormone levels that occur throughout a woman's life. These changes are evident during puberty, pregnancy, and menopause, as well as after giving birth or experiencing a miscarriage. In addition, the hormone fluctuations that occur with each month's menstrual cycle probably contribute to premenstrual syndrome, or PMS, and premenstrual dysphoric disorder, or PMDD -- a severe syndrome marked especially by depression, anxiety, and mood swings that occurs the week before menstruation and interferes with normal functioning of daily life.