Is there an ideal number of minutes after actual sunrise for the earliest morning sun to have an optimal effect on SAD and circadian rhythm?

By “optimal effect,” we assume you mean antidepressant and circadian phase-advancing effects. 10,000 lux, the high-dose standard for white light therapy, occurs outdoors about forty minutes after sunrise.  But that’s too pat an answer.  Studies of dawn simulation show that antidepressant and circadian effects begin before sunrise.  Dawn is a continuous event that may last 90 minutes or longer.

Based on New York data, the average SAD patient experiences remission of winter depression during the first week of April, with sunrise around 6:30 AM.  There is a wide spread of dates across individuals, though.  In most cases, remission occurs as early as the spring equinox around March 20-22, with sunrise around 6:55 AM, and as late as the start of May, with sunrise around 5:45 AM.

These statistics indicate that a person’s chronotype (as determined by our AutoMEQ questionnaire) influences the time of day when sunrise — and the dawn that precedes it — will have optimal effect. Evening chronotypes may respond best to light therapy at 8 AM or later, while morning chronotypes may respond best at 5:30 AM or earlier.

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.

I am considering using a light box to adjust my circadian rhythm, which is now severely delayed. I live in an apartment with large windows providing lots of daylight. At night, a nearby parking lot provides some light through my blinds. I recently bought a large sleep mask, as putting up blackout curtains could create problems with my landlord. Is my approach reasonable, or totally illogical?

To correct delayed sleep phase, there are two principles and procedures to keep in mind: (1) Restrict light exposure as much as possible in the evening and at night until about 1.5 hours before wake-up time. (If your wake-up time is in the mid- to late morning, minimizing light exposure will be important throughout early morning.) Before sleep, you want to turn down the lights to a comfortable level for reading or watching TV, but nothing more. During sleep, even low levels of light can be counterproductive, so consider adding dark curtains inside your blinds to block light from the parking lot. (2) Starting at wake-up time, or 1.5 hours earlier, you want to enhance light exposure to counteract your delayed rhythm. Since your bedroom will be dark, you cannot utilize light through the windows.

There are two complementary solutions: First, you can use a dawn simulator for 90 minutes before wake-up time, or simply an appliance timer to turn on bedroom lights. Second, 30 to 60 minutes of bright light box therapy will be helpful when you wake up–a good time for breakfast and reading the newspaper. Over a couple of weeks, move your wake-up time (and light exposure) gradually earlier–say, 15 minutes every three days. Before long, you can expect to normalize your delayed pattern.

Does time of day matter when undergoing surgery? I realize that a patient is at the mercy of the hospital scheduler, but as a night person, would I do better to opt for morning or afternoon? Or is the circadian rhythm of the surgeon a more important determinant? After all, he should be at his peak of energy and alertness when he operates.

Very provactive questions, with no easy answer. Consider also that there are daily rhythms of sensitivity to anesthetics and pain tolerance, which are not necessarily in synch with your behavioral tendency toward eveningness. There may well be times of day when you could achieve full anesthetic effect at far lower dose, and with shorter stay in the recovery room. The best place to read about these possibilities is in The Body Clock Guide to Better Health, listed at the top of the Recommended General Reading list at //

Do people who suffer from SAD usually have circadian rhythms that are somewhat “off”? I am just curious since you have said that the best antidepressant effect comes from resetting the internal clock earlier. Do people who have “normal” circadian rhythms tend to not get SAD?

On the one hand, we could say that the circadian rhythms are “off” during winter depression, in the sense that relief is obtained by shifting the rhythms earlier. Furthermore, come springtime, it appears that the internal clock spontaneously shifts earlier, at least for people who are “evening types” in winter. (To check your chronotype, take the Automated Morningness-Eveningness Questionnaire at On the other hand, SAD patients can be morning types, intermediate types or evening types — the same distribution that exists in the healthy, non-depressed population. What appears different about people with SAD is their mood lift when light therapy shifts the internal clock earlier, regardless of chronotype.

I would like to know what to do about my severely advanced circadian rhythm!

Here are some strategies: (1) Keep your room lights bright all evening before you go to sleep. (2) Use bright light therapy an hour before you go to sleep, and edge it later as you start sleeping later. (3) Keep your shades drawn to avoid dawn and early daylight exposure. (4) Try the lowest possible dose of immediate-release melatonin (0.1 mg) as soon as you wake up, but be sure not to go into bright light, including outdoor light, for at least two hours. (5) Wear dark sunglasses whenever outdoors in the morning. An alternative, for better visibility, would be 4% dark-orange wrap-around’s from Readers may notice that these strategies are generally opposite to those used to counteract the more common delayed sleep phase syndrome. They are also opposite to the general strategy for treating depression. Any of these strategies may work on their own, but in all likelihood you’ll need to find an effective combination.