A reader asks:

I’ve had Delayed Sleep Phase Disorder for more than fifteen years, and mood problems, too. However, my question is about the start time for light therapy.

I have developed sleep disruption (waking up in the middle of “my night” and falling back asleep two to three hours later). Even though I don’t drink coffee, or even eat sugar, I’m hit up from all sides, and I don’t have a regular daily wake up time. It’s fairly hellish.

Generally, I wake up between 11 am to noon or 1 pm wake. I fall asleep around 3 to 3:30 am, come hell or high water. Depending on if I sleep straight through or not, I wake up anywhere between 9:30 am and 1 30 pm.

My question is: When should I start daily light therapy? I’m most rested at about 11 or noon, but if I wake up earlier because of sleep disruption, should I just skip that day?

Finally, I don’t have an expert to work with here in my city, and I don’t quite understand the phrase, “moving the start time back to thirty minutes after a few days.” Does that mean you believe the client will be falling asleep thirty minutes earlier after only three days?
With so much thanks.


You are suffering from intermittent interrupted sleep.  When you sleep through without interruptions, you’re up at 9:30 am.  Otherwise, you compensate with a “second sleep” that can end at 1:30 pm, four hours later.  You don’t say when you fall asleep at the start of the night.  If in fact you have Delayed Sleep Phase Disorder (DSPD), we would guess you fall asleep around 1:30 am, since 1:30 to 9:30 gives an eight-hour sleep duration, even though it is delayed relative to a typical 11 pm bedtime. 

If this describes your situation, you would aim to start light therapy when you woke up at 9:30 am, and continue to fall asleep late. 

Some likely complications: 

1. You may find yourself waking up well before 9:30 am for several days, according to your current interrupted pattern.  In that case, stay awake until 9:30 am for the light therapy session.

2. After the session, you may want to go back to sleep.  Stay awake for the day, however.  This will build up sleep pressure and make it easier to start falling asleep before 1:30 am, while reducing the interruptions.  Take advantage of that — it will help you progress more rapidly toward your goal of an earlier bedtime.

If you get this far, you should be sleeping a solid eight hours starting at 1:30 am.  Now you are ready to shift your sleep episode earlier.  Try shifting wake-up time + lights earlier in fifteen-minute steps  every few days, using an alarm clock. If you are lucky, you will fall asleep earlier and earlier effortlessly as you advance wake-up time, and you will still get an eight-hour block of sleep.  

However, bedtime is an ingrained habit for many people, and might not respond immediately with the shift to earlier wake-up times. In that case, you’d find yourself sleeping fewer and fewer hours as you try to wake up earlier.  Within several days, however, sleep deprivation will build up sufficiently and you’ll suddenly switch to an earlier bedtime, falling into sync with the desired schedule. In the evening, don’t get into bed until you feel ready to sleep, and avoid bright light exposure for three hours before anticipated bedtime.

Keep a sleep log throughout, so you can monitor your progress as well as fallbacks.  This plan is not easy without professional monitoring and supervision. However, it is not impossible, and it’s worth a try. It may be easiest to wait for vacation, so your workday isn’t disrupted in the process.

After your schedule stabilizes, you can try light therapy in the morning to improve your mood. To find out how to do that, and what time of day is best for you personally to begin a session, read Light Therapy for Beginners: Six Steps.