Reviews Health & Medicine Internal Time Chronotypes, Social Jet Lag, and Why You're So Tired by Till Roenneberg By Science News June 15, 2012 at 12:43 pm - More than 2 years ago Share this:Share Share via email (Opens in new window) Email Share on Facebook (Opens in new window) Facebook Share on Reddit (Opens in new window) Reddit Share on X (Opens in new window) X Print (Opens in new window) Print 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