AFAIK, there are no long-term (30+ year) studies comparing women who have never-used, briefly-used, and long-term-used hormonal drugs to suppress their menstrual cycle. The Women's Health Initiative found that prescription horse piss (PREMARIN, made from PREgnant MARes' urIN) was not good for women's health.

I have personally used non-prescription Progesterone USP to recover from a head injury, so I'm inclined to believe the heretical scientists who heckle the birth control peddlers.