Mary Harrington researches circadian rhythm entrainment.  Her past research has been on neural systems mediating entrainment, in particular non-photic entrainment pathways utilizing neuropeptide Y and serotonin. Currently she is investigating the role of circadian disruption in health. 

One line of research examines effects of pro-inflammatory cytokines on circadian rhythms, in work related to fatigue and sleep disruption associated with illness, stress, and aging. She is also characterizing mouse models of jetlag using mice with a bioluminescent report for the circadian clock protein Per2. She is also conducting experiments on cultured hepatocytes to better understand cell coupling in the circadian clock in the liver.