In TCM, as in many other cultures, the health and medicine of female bodies was less understood than that of male bodies. Women's bodies were often secondary to male bodies, since women were thought of as the weaker, sicklier sex. Yin and Yang were critical to the understanding of women's bodies, yet they were only understood in conjunction with male bodies. Women's diseases were harder to treat and cure in the eyes of many cultures, but especially in TCM. Finally, social and cultural beliefs were often barriers to understanding the female body.