The time of day to use bright light - Business

The time of day to use bright light

For many people, bright light at any time of day will help depression. Some tests comparing morning, afternoon, and evening bright light treatments show about equal results with any time of use. There is some evidence that many SAD patients may do better with morning light (not every study agrees), but that may not be because of the seasonality of the depression, but possibly, because SAD patients tend to sleep late. I think it is the sleep pattern which provides the most useful clue to optimal timing.The principles for optimizing light timing from sleep patterns are simple. If a person tends to have trouble falling asleep and has trouble getting up on time each morning, that person is likely to do best with using bright light early in the morning. People whose depression is linked to sleeping more may also tend to do best with light in the morning. For such people, using bright light immediately after awakening is the most effective time to use bright light. Indeed, some studies suggest that getting up a bit early to use morning bright light increases its benefit. Dr. Terman recommends beginning morning light treatment about 2 ? hours after the middle of sleep. For example, if a person sleeps from midnight to 8 AM (with midsleep at 4 AM), the recommended time would be 6:30 AM. In contrast, evening bright light may be best for the person who tends to nod off early in the evening, who cannot stay awake for prime time television, and who awakens earlier than desired in the morning. For the person who does not fit clearly into either of these patterns, there might be little difference between morning and evening bright light treatment, and midday or afternoon bright light might work well also. We will explore these principles in more detail in the section on advanced and delayed sleep phase syndromes.

For the person suited for morning light, a way to get fast relief is to use wake therapy. The way to use wake therapy is to get up in the middle of sleep, turn on bright room lights, and stay awake for the second half of the night (e.g., a person who sleeps from midnight to 8 AM would get up at 4 AM.) Then, bright light treatment is commenced near the normal awakening time. Most depressed people experience surprising relief of depression after getting up so early, provided they stay awake all day despite some increased sleepiness. Although patients who are not using bright light tend to relapse after wake therapy as soon as they sleep again, with bright light treatment, the rapid gains of wake therapy are often maintained. I believe that a single night of wake therapy (getting up in the middle of the night) is helpful and practical at the beginning of light treatment.A special case are the patients with bipolar disorder (a history of being manic-depressive), especially those whose mood cycles rapidly between mania and depression. These patients may be prone to trigger unwanted and serious mania with use of bright light, especially in the morning, or with wake therapy. Mid-afternoon bright light may be the best for these patients, according to preliminary testing. I do not recommend wake therapy for bipolar patients, because of the risk of mania.

The most important aspect of treatment lighting is that it be very bright. So far as we know, sunlight and artificial lighting work equally well. However, in various climates, environments, and social situations, using sunlight may be impractical, so most people will need to buy, rent, or borrow special artificial lighting. So far as we know, both ceiling lighting and lighting level with the eyes work equally. There is some indication-not yet proven clinically-that light coming from below (e.g., a light on the floor) would not work as well.So far as we know, diffuse incandescent and fluorescent light of equal brightness might work equally, but there are two important advantages with fluorescent fixtures. First, since fluorescent lighting is more energy-efficient, you pay for less electricity and produce less wasted heat with fluorescents. That heat could be annoying in the summer. Second, fluorescent tubes are large, so it is easy to diffuse the light over an area of several square feet. This means that unlike the very bright point of light produced by incandescent bulbs, fluorescents produce somewhat dimmer light over a larger area. When the light goes through the lens of the eye and hits the retina (the back of the eye), the energy of diffuse light is spread over a large area, so it should not heat the retina or make you see spots (like the spots you see after looking at a flash bulb). Diffused bright light is safer for the eyes and will cause less strain. As a general rule, you could not burn your retina by staring at any of the common fluorescent bulbs with diffusers, even if you are receiving 10,000 lux. Obviously, nobody should stare at a light if it hurts or seems to dim the vision. Some people are annoyed by the flicker or sound of older fluorescent ballasts, so fluorescent fixtures with electronic (high frequency) ballasts will probably cause less headache and sense of eye strain. Avoid the older models flickering with the 60 cycles household alternating current.

I am not certain that staring at very bright incandescent bulbs is entirely within the range of safety. I would never recommend that anyone take any unnecessary chances with their eyes, so I feel that nobody should treat themselves by looking directly at bright incandescent light (such as 300 watt halogen bulbs) without diffusers. Indirect incandescent lighting or lights with large diffusers or shades should be safe, as I will discuss in the section about using lighting for the elderly. The problem with using indirect incandescent lighting for treating depression is that the standard commercial lamps lose most of the brightness by bouncing the light off the walls and ceiling, partly because the light travels a greater distance. As a result, the lighting store "torchiere" incandescent lamps are probably not bright enough to do the job well for serious depressions. Another problem is that the 300-500 watt halogen incandescent bulbs used commonly do not last very long and may be a bit difficult to replace. For these reasons, all of the lighting fixtures which I can currently recommend for significant depression use fluorescent bulbs and diffusers.

Several manufacturers (listed in the box below) make fluorescent fixtures which do a very nice job of helping depressed patients. A good place to find lighting manufacturers is at In general, 160-300 watts of fluorescent light illuminating a bright diffuser about 1 yard from the eyes will give about 2000-3000 lux. The exact brightness depends on various aspects such as the bulbs, the diffusers, and the reflectors. To get 10,000 lux, the manufacturers may recommend a somewhat bigger fixture with more wattage or placing the fixture closer to the eyes, perhaps 12" to 18". There is considerable difference in the brightness of different models, so the dimmer models may need to be closer to the eyes. Some of the designs hold the light tilted a bit above the eyes, which seems to be convenient for getting light treatment and also getting something done reading, writing, eating, or watching TV.

Some researchers have recommended that people stare at the fluorescent diffuser most of the time when they are getting the treatment. Others have recommended glancing at the light every minute or two. Others seem to feel that having the light source anywhere in the field of vision (even if you aren't looking at it directly) is just as good. Unfortunately, we really do not know yet whether it makes much difference whether you look directly at the lighting. Most evidence suggests that having the light within the field of vision and glancing at it occasionally is sufficient. Also, unfortunately, we really do not know if it makes a difference where the light is during treatment: above the eyes (tilted), straight in front, to the side, or even below where the person is looking. There is some evidence-not fully convincing--that light slightly above or even with the eyes would be more effective than light coming from below where the eyes are looking.

I wish we had some sort of independent testing of different brands and models of bright lights, to see which ones helped depressed people the most. We do not. Comparative testing would be difficult and expensive, so almost none has been done. I suppose that all of the fluorescent light boxes quoted to give the same brightness are likely to be roughly equivalent, but I do not really know.A lot has been written about natural lighting and whether one should use lighting with a "full" spectrum. I suspect this spectrum of claims is largely baloney! In fact, the FDA forced one company advertising "full spectrum" light into a consent decree admitting that their claims were deceptive. First of all, almost any white light produces the full visible spectrum of colors (light wave lengths). The question is the balance of the different wavelengths, which does differ from one light source to another. If one looks at the fine spectrum with a precision spectrophotometer (which measures the color balance of light exactly), I doubt that any of the commercial sources really produces a light spectrum which could be mistaken for the rather smooth spectrum of natural sunlight. Fortunately, the eye is not a spectrophotometer, and there is no evidence that the sunlight spectrum is necessary.

The main issue is how much ultraviolet light the light source produces, because some of the "full spectrum" bulbs give off enough ultraviolet to possibly increase cataracts or skin cancer. There is no evidence that the ultraviolet is needed for the bright light treatment benefit, so needless to say, I do not recommend anything with significant ultraviolet. Most of the fluorescent manufacturers use a plastic diffuser which filters out the harmful ultraviolet. There is more discussion of the risks of ultraviolet in the chapter about risks. It is true that many Americans get so little ultraviolet sunlight in the winter that they become vitamin D deficient, especially when fear of obesity unwisely persuades people to avoid Vitamin-D-fortified dairy products. It is sun striking the skin, not the eyes, which helps with Vitamin D, so if you are going to a tanning saloon for Vitamin D, keep the ultraviolet out of your eyes. Then light up your eyes without the ultraviolet. Anyone concerned about vitamin D would probably be wiser to buy some in the grocery store than to try ultraviolet lighting to prevent vitamin deficiency. Dairy products can be good for you. Did you know that you might actually get depressed, if your cholesterol is too low?

In terms of color, almost all of our research on light treatment uses white light, which clearly works. There is some speculation that green light or blue-green may be the best part of the color spectrum for treating depression, but do not worry about that, because we really are not sure yet. Anyway, all of the usual white light sources have plenty of green.There has been a good deal of hoopla and advertising about light visors. The idea is that if you could wear the light source on your head like a baseball cap--and get bright light treatment without blinding yourself--it might be easier to go about your business. I never recommend light visors, because I am not the least bit convinced that they work for treating depression. In fact, there have been several studies suggesting that various light visors which have been tested do not work better than a ineffective dummy treatments.Apparently a more promising approach to making light treatment easy is providing light exposure during sleep. There is some evidence that gradually increasing light toward the end of the night, simulating dawn, has a useful effect. I do not think that the dawn simulation idea has yet been proven superior to using a steady intensity of light during sleep. There has not yet been sufficient research on this technique from different laboratories. I do not recommend trying dawn simulation unless it is quite impossible to arrange for sufficient light when you are awake, but some manufacturers provide dawn simulation devices, if you want to take a chance on trying light before waking up. Light before waking up is a form of morning light, and it probably will work best for people with trouble falling asleep and with trouble getting up on time.If you tried bright light and you felt better, what do you do next? Many people should keep using light. Often, our need for bright light is not temporary. Depression may be a long-lasting problem, not temporary like a sore throat. If you need supplemental light, you may need light supplements for years, or at least until your habits change. You would not expect your need for food or exercise or sleep to be temporary. You would not expect a rose bush to need time outdoors only occasionally. These can be life-long needs. For some people, a need for light might also be life-long.

Therefore, some people who benefit from bright light need to use bright light almost every day for years.

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