Schernhammer's research interest is in exploring the exposures that influence the circadian system in humans and health consequences. She has done work on the effects of light at night on cancer risk through the melatonin pathway and demonstrated that the effects of light at night may affect not only breast cancer, but also other cancers such as colorectal cancer, generating evidence that supports a new hypothesis on the development of cancer. She has also conducted urinary melatonin measurements in the Nurses' Health Study to assess the hormone's variations according to shift work status and its association with breast cancer risk in the Nurses' Health Study. Current projects study the role of clock genes in these associations and melatonin's cancer preventive potential.