I haven't heard of "Yaz" but i used to be on a pill called "Yasmin" many moons ago (for endo) and that definitely made my periods lighter - i went from having 7 days of very heavy, painful bleeding to 4 days of light to moderate bleeding- i had to go off it for other hormonal reasons tho and haven't been back on any pill since.
:yeahthat: I have never heard of Yaz? Does sound good though? Have you tried google?

Good luck xoxo