Reviews Health & Medicine Internal Time Chronotypes, Social Jet Lag, and Why You're So Tired by Till Roenneberg Share this: Share via email (Opens in new window) Email Click to share on Facebook (Opens in new window) Facebook Click to share on Reddit (Opens in new window) Reddit Click to share on X (Opens in new window) X Click to print (Opens in new window) Print By Science News June 15, 2012 at 12:43 pm Depression, weight gain and sickness are just a few of the health risks when internal biological clocks fall out of sync with daily life, a chronobiologist warns. Harvard Univ., 2012, 272 p., $26.95