Chronotherapy is a behavioural treatment that attempts to move bedtime and rising time later and later each day, around the clock, until a person is sleeping on a normal schedule.
[1] This treatment can be used by people with delayed sleep phase disorder (DSPD), who generally cannot reset their circadian rhythm by moving their bedtime and rising time earlier.
DSPD is a circadian rhythm sleep disorder, characterised by a mismatch between a person's internal biological clock and societal norms.
Animal studies have suggested that such lengthening could "slow the intrinsic rhythm of the body clock to such an extent that the normal 24-hour day no longer lies within its range of entrainment.
"[6] Czeisler CA, Richardson GS, Coleman RM, Zimmerman JC, Moore-Ede MC, Dement WC, & Weitzman ED.