One study found increased breast cancer risk only with teenage (<20 years) OC use (OR=1.53 (95% CI 1.17–1.99) per year of use at age <20 years) (Jernstrom et al, 2005), and in the others there was even a suggestion of decreased breast cancer risk within BRCA1 carriers (OR=0.22, 95% CI 0.1–0.49 for OC use of at least 1 year) (Milne et al, 2005). This evidence concerns the gene BRCA1 and breast cancer.