A reader asks:

 I am 34 years old and have a long history of difficulty sleeping. My doctor diagnosed me with delayed sleep phase disorder (DSPD). It appears that my “normal” sleep time is 4 or 5 a.m., and I typically wake up around noon or 1 p.m. I would like to shift my sleep earlier so that I can fall asleep around midnight or even 11 p.m. I purchased a light box per my doctor’s instructions, but he is not sure how/when to apply the light box. What time should I use the light box? Immediately upon waking at noon? If I do so any earlier, it will disrupt my sleep.


Each case of DSPD needs individual clinical consideration because multiple factors can cause the sleep pattern, and therefore approaches to treatment will vary.  Thus we can only suggest a broad strategy here.  Light therapy can start at your current wake-up time, as you say. However, waking up for light therapy half an hour earlier than usual may speed up progress.

In conjunction with morning light, it is critical to control bright white (and bluish) illumination for several hours before sleep. Ways to do this include using blue-blocking glasses, such as the protective lenses we recommend on our site. You can also install f.lux software, available for free, on your computer, and Night Shift software on your iPad and iPhone.  Room light should be kept low, but comfortable, allowing clear vision at a distance.  Refrain from eating for at least three hours before current, expected sleep onset.

The bedroom should be dark, ideally with blackout shades for protection from the dawn twilight and early morning sunlight during hours you are sleeping. Given the darkness of the bedroom, it is helpful to set a bedside dawn simulator to provide increasing light, from darkness to maximum illumination, in the 30 minutes before you need to get up.  Set an alarm clock for back-up in case you don’t wake up spontaneously to the dawn signal.

If you are not oversleeping, after a few days, it will be time to begin shifting wake-up time progressively earlier, probably in 30-minute steps every 3-4 days.  Dawn simulation and post-awakening bright light therapy should be shifted together. Be careful not to rush the process. If you shift too rapidly, you may find yourself flipping into a delayed sleep pattern even more extreme than when you started. Therefore, the process requires close attention. Make sure you are waking up comfortably at each new wake-up time  before you try shifting your wake-up time 30 minutes earlier. Each 30-minute change may take just a few days, or require a week.

The dose of bright light therapy can make all the difference. The best length of time for a session at 10,000 lux can vary substantially between individuals. Thirty minutes will be effective for some people, but others will need 45 or even 60 minutes. Keep in mind that you may be successful at waking up earlier long before you are successful at falling asleep earlier to the same extent. Consequently, there may be an interval of days, or even weeks, when you don’t get as much sleep as usual.  At some point, however, you should be able to compensate for earlier waking with earlier bedtimes. Look for signs that you are starting to get sleepy earlier than expected, and yield to your sleepiness rather than continuing nighttime activities. However, don’t force yourself into bed before you get sleepy.

Beyond this general strategy, you may also need to practice good sleep, or consider the influence of your medications on sleep.

In short, you will be lucky if you can pull off this change on your own, without a clinician’s monitoring and guidance throughout. That said, many people have had such luck, and it is well worth the trial, even if it fails.