In this section, you’ll get a better understanding of factors that may affect your breast cancer risk.
Some factors increase breast cancer risk and a few lower risk. Some affect risk a great deal and others by only a small amount.
Although we’ve learned a lot, we still don’t know what causes breast cancer to develop at a certain time in a certain person. It's likely a combination of risk factors (some of which are still unknown).
However, why a certain combination of factors might cause breast cancer in one person, but not in another, is still unclear.
The data in this section come from 2 main types of research studies:
The goal of these studies is to give information that helps support or disprove an idea about a possible link between an exposure (like alcohol use) and an outcome (like breast cancer) in people.
Although they have the same goal, observational studies and randomized controlled trials differ in:
Learn more about different types of research studies.
Animal studies add to our understanding of how and why some factors cause cancer in people.
There are many differences between animals and people however that make it hard to translate findings directly from one to the other.
Animal studies are also designed differently than human studies. They often look at exposures in larger doses and for shorter durations than are suitable for people.
While animal studies can lay the groundwork for research in people, we need human studies in order to draw conclusions for people.
All data presented within the About Breast Cancer section of this website come from human studies.
Some organizations conduct research and/or prepare summary reports of research on certain factors shown to have a link (or no link) to breast and other types of cancer.
Good places to find detailed, reputable up-to-date information (for example, if you have concerns over a news item on cancer) include:
IARC is a part of the World Health Organization. The CDC, NTP and FDA are all part of the U.S. Department of Health and Human Services.
Breast Cancer 101 - Risk Factors
Facts for Life: Breast Cancer & Risk
Research Fast Facts: Breast Cancer Inequities