Chronotherapy (sleep phase)

In chronotherapy, an attempt is made to move bedtime and rising time later and later each day, around the clock, until the person is sleeping on a normal schedule. This treatment can be used by people with delayed sleep phase disorder who generally cannot reset their circadian rhythm by moving their bedtime and rising time earlier.

Example
Here's an example of how chronotherapy could work over a week's course of treatment, with the patient going to sleep 3 hours later every day until the desired sleep and waketime is reached. (Shifting the sleep phase by 3 hours per day may not always be possible; shorter increments of 1–2 hours are needed in such cases.)


 * Day 1: sleep 04:00 to 12:00
 * Day 2: sleep 07:00 to 15:00
 * Day 3: sleep 10:00 to 18:00
 * Day 4: sleep 13:00 to 21:00
 * Day 5: sleep 16:00 to 00:00
 * Day 6: sleep 19:00 to 03:00
 * Day 7 to 13: sleep 22:00 to 06:00
 * Day 14 and thereafter: sleep 23:00 to 07:00

While this technique can provide temporary respite from sleep deprivation, patients may find the desired sleep and waketimes slip. The desired pattern can only be maintained by following a strictly disciplined timetable for sleeping and rising.

Other forms of chronotherapy
A modified chronotherapy is called controlled sleep deprivation with phase advance, SDPA. One stays awake one whole night and day, then goes to bed 90 minutes earlier than usual and maintains the new bedtime for a week. This process is repeated weekly until the desired bedtime is reached.

Sometimes, although extremely infrequently, "reverse" chronotherapy – i.e., gradual movements of bedtime and rising time earlier each day – has been used in treatment of patients with abnormally short circadian rhythms, in an attempt to move their bedtimes to later times of the day. Because circadian rhythms substantially shorter than 24 hours are extremely rare, this type of chronotherapy has remained largely experimental.

Side effects
The safety of chronotherapy is not fully known. While chronotherapy has been successful for some, it is necessary to rigidly maintain the desired sleep/wake cycle thenceforth. Any deviation in schedule tends to allow the body clock to shift later again.

Chronotherapy has been known to cause non-24-hour sleep–wake disorder in at least three recorded cases, as reported in the New England Journal of Medicine in 1992. 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."

Recommended reading
Czeisler CA, Richardson GS, Coleman RM, Zimmerman JC, Moore-Ede MC, Dement WC, & Weitzman ED. (1981). Chronotherapy: Resetting the circadian clocks of patients with delayed sleep phase insomnia. Sleep, 4, 11–21.