Fragmented day-night cycle induces period lengthening, lowered anxiety, and anhedonia in male mice.

Light exposure at night disrupts circadian-regulated biological functions, including mood. However, the consequence of fragmenting the night period and distributing it across the 24-hr period is less understood. Here we show that fragmenting an 8 -h and 6 -h night into equally distributed 2 -h periods throughout the 24-hr day results in period lengthening of the circadian rhythm in mice.