Circadian Rhythm Disorders Guide

Deep in the brain, just above the optic nerves, sits a small group of cells called the suprachiasmatic nucleus. It is the body's master clock. It tells the rest of the body whether it is day or night, and governs when you wake, when you get sleepy, when body temperature falls and when melatonin is released.

The clock runs on its own, about 24 hours per cycle. But it is reset every day, and the most important reset signal is light reaching the eye. Light in the morning sets the clock earlier. Light in the evening and at night sets it later. Meals, activity and regular habits help too, but light counts most.

The lowest point of the clock is called the nadir. For most people it falls around four in the morning. Body temperature is lowest then, and being awake is hardest. Light just after the nadir moves the clock earlier. Light before the nadir moves it later.

Many people with delayed sleep phase have heard all their lives that they just need to pull themselves together, go to bed earlier and get up at a normal time. Most have tried, many times. It works for a few days, then it crashes.

The reason is that the alarm clock can be moved, but the biological clock does not move because you got up. Getting up at 07:00 when your clock says it is the middle of the night is like being woken at 03:00 every single day. It is hard to fight your own body, and it is not a lack of discipline.

Circadian rhythm disorders often run in families, usually begin in the teens and tend to soften with age. They can occur together with other problems, not least insomnia, anxiety and depression. Then both need to be taken seriously.

Treatment is not about forcing yourself to sleep, but about moving the clock itself. The two things that matter most are getting up at the same time every day and getting light in your eyes right after you get up. Timed melatonin and less light in the evening can be added on top.

Get up at the same time

The clock is set by when you get up, not by when you go to bed. So a fixed rise time, weekends included, is the first and most important step. In treatment the time you have now is stabilised first, before it is moved gradually.

Light at the right time

Bright light in the hours after the nadir moves the clock earlier. Light in the evening and at night moves it later. So daylight or a daylight lamp is used right after you get up. Dimmed light or blue-blocking glasses in the evening can be added to stop the clock drifting later again.

Melatonin as a supplement

Melatonin is not a sleeping pill but a signal to the clock that evening has come. In circadian treatment it is given as a fast-release tablet, not a slow-release one, about twelve hours before you plan to get up. It is a supplement to a fixed rise time and light, not a replacement.

Chronotherapy in three phases

First the rhythm you have now is stabilised. Then it is moved gradually, often half an hour a week. Finally the new rhythm is stabilised. It takes time, and it is easier when you do not have to move everything at once.

A week-by-week plan

Enter when you think you can get up the first week, and when you want to get up in the end. The plan holds the first time for one week, then moves it half an hour a week until you arrive, and holds the new time the last week. The further the clock has to move, the more weeks it takes.