<qa>  What is the demand for effective therapies to treat PPD?PPD causes significant distress to a large number of women; the demand for effective therapies to treat PPD is considerable. Estradiol therapy has a prophylactic effect in women at high risk for developing PPD. The prevention of a decline in estradiol levels may prevent the onset of PPD. Studies also suggest that estradiol has antidepressant effects in women and may provide a safe and effective alternative to traditional antidepressants in women with PPD. 