Is it true that for society in general, people have a mind of their own by disrespecting or not taking account of their circadian rhythms, especially in cases of undiagnosed, Delayed or Advanced Sleep Phase Disorder (DSPD, ASPS)?

Thank you for this provocative question. Surely, it is true that most people with DSPD and ASPS, although they realize their sleep is displaced relative to the norm, do not identify the situation as a “disorder” or attribute it to their circadian rhythms. Many of them accommodate it by making a circle of friends with similar sleep patterns (active phone calling after midnight, etc.) and finding jobs that do not require a 9-5 work schedule (bartending, acting, free-lance writing, etc.) Importantly, however, many also experience depression, and cannot maintain self-supporting employment or family life. Some, with partners who sleep normal hours, develop serious conflicts at home (even with the threat of divorce). When such problems develop, you will recognize that you have a serious problem, but still you are unlikely to attribute it to a circadian rhythm disturbance.

The Center for Environmental Therapeutics has a major goal of teaching people with ASPS and DSPD the nature of the problem and guiding them toward effective treatment and adjustment using the most potent method available–light therapy. Light therapy needs to be complemented with restricted lighting at other times of day in order to normalize the sleep pattern. In DSPD, for example, it is important to receive ample light exposure after sleep, but to minimize light exposure before sleep. The opposite holds for ASPS. People have achieved dramatic improvement using these simple techniques.

Do most people respond to light therapy even at the “right time” for phase advances or delays? Does it need to be done at late night or early morning when it is dark?

The circadian rhythm system is most responsive to light–producing phase shifts–when it is done therapeutically at the edges of a person’s “subjective night.” What is subjective night? It’s not the same thing as night outdoors. People vary by as much as six hours (early types, late types; larks, owls) in their subjective night. How can you find out about your subjective night and the specific time that morning light therapy is expected to work best for you (by phase advancing your internal clock)? Complete our Automated Morningness-Eveningness Questionnaire at, and you’ll find the answer.

Is it possible to have a rare case of extreme advance of sleep, which means you get tired, earlier and earlier in the day, but without depression? It is actually the opposite of delay phase. The condition was caused by seeing light at the wrong time of the day, causing a phase advance, repeated again and again, leading to a very bad situation–really early sleep onset morning/afternoon with insomnia at night. Do you have suggestions to correct this rare case?

Yes, the advanced sleep phase syndrome is opposite to the more prevalent delayed sleep phase syndrome. This may be caused by inappropriate light exposure, a genetic predisposition for a fast internal circadian clock, or both. You indicate that before your repeated light exposure at the “wrong time of day” you did not experience the problem, so the cause appears to be environmental. Yet, it seems that the problem did not resolve after you eliminated the problematic lighting exposure. We would need to know much more about your abnormal sleep, and also your work schedule, in order to make a specific recommendation (which is beyond the scope of this forum).

However, we can offer some general hints. Using bright light therapy just before your daytime sleep episode (say, noontime), followed by restricted light exposure (strong wrap-around sunglasses) for the rest of the day after you wake up, should begin to move your internal clock later. As this happens, you can delay the light exposure accordingly, until you are going to sleep in the late evening (say, 10 p.m.). You can expedite the process by taking a low dose of melatonin (say, 3 mg) when you wake up in late afternoon or early evening. Be careful never to use melatonin when exposed to bright outdoor or indoor light. Caveat: If you are getting significant sleep at night, beyond your daytime sleep, the solution would require clinical consultation with a sleep clinician.

I experience advanced sleep phase syndrome (ASPS) in addition to SAD. My understanding of SAD is to treat it with morning light. My understanding of ASPS is to treat it with evening light. Which time of the day should I schedule my 30-minute light box treatment?

This is a terrific question. For our readers, ASPS is a circadian rhythm sleep phase disorder in which one falls asleep unusually early (say, 8 p.m.) and wakes up unusually early (say, 3 a.m.). To set the circadian clock to a later hour, light therapy has to be taken around the start of the “subjective night” (say, 8 p.m.), because morning light could shift the sleep cycle even earlier. On the other hand, light therapy for SAD is most effective at the end of the subjective night (say, 6:30 a.m. for a normal sleeper), and even those with a strong morning chronotype benefit most from morning light. (For a determination of your chronotype, complete the Morningness-Eveningness Questionnaire at

The chronotype of people with ASPS falls outside the range of normal chronotypes, and their antidepressant response to morning vs. evening light has not been adequately investigated. This may be a case where treatment should be scheduled in both morning AND evening, as was the original formula for SAD treatment. The specific timing of the two treatment sessions would need to be determined by a specialist, with the goal of delaying the sleep episode while maintaining morning exposure (in the case above, at, say, 6:30 a.m.). One technological means to implement such a schedule is with a dusk-to-dawn simulator used to straddle the sleep interval in the bedroom. A high-intensity dusk signal could be followed by a lower intensity dawn signal, to achieve an optimum balance. We definitely need more research on such applications.