Again, researchers were unable to determine if Depo Provera caused the breast cancer or merely accelerated its growth. In particular because North American women, at one in eight, have a much higher incidence of breast cancer than do women in Thailand, Kenya and Mexico, and because North American women have been and continue to be exposed to hormonal contraceptives and other drugs from a much earlier age and for much longer than Southern women. The combined effect of long-term exposure to synthetic hormones is not well known nor well evaluated. Depo Provera and Bone Density Also troubling are the recent data on Depo Provera's impact on bone density, particularly among teenagers - Depo Provera's target market. Several studies have documented that Depo Provera increases loss of bone density.
Findings suggest that the loss progresses the longer the use.
New Zealand studies have documented bone density loss of up to 8 per cent. One 1996 U.S. study, looking at teenage girls, found that after two years use, girls on Depo Provera had lost 3.1 per cent of their bone density. This at a time when girls are naturally increasing their bone density as they grow and mature. A 1994 British study suggests that once women stop using Depo Provera they regain some, but not all, of the lost bone density in most bones of their body. Researchers are calling for a longer term assessment of Depo Provera's impact on bone density.