Light Therapy

About Light Therapy, Seasonal Affective Disorder (SAD), Depression & Melatonin.
by Gila Lindsley, PhD., A.C.P.

The following is an excerpt from Dr Gila Lindsley article, the full article can be downloaded as a PDF file from this link. » FULL ARTICLE

SAD Symptoms

Depression that responds to light

For those who turn within and become SAD with the coming of the cold, dark months the consequences can be very severe. I’ll never forget the first patient I saw with severe SAD. It was in the winter of ’87 I think, or perhaps it was ’88. I was running a Sleep Disorders Center in a New Hampshire psychiatric hospital and had become very interested in SAD as well. The patient in question was a woman who was 35 or so. She was an emergency admission because she had tried to commit suicide, and darned near succeeded. I was shaken. I hadn’t realized until then that SAD could be so life threatening. When I talked to her I found out that she felt SAD every winter, but generally was able to hang on until her kids’ February vacation from school when the family took a vacation in sunny Florida, which immediately lifted her spirits. “What happened this year,” I asked her. “‘February’s vacation didn’t come until the first week of March. I couldn’t hold out any longer.” On so little did so much hang.

We treated her with bright light therapy, and discovered soon thereafter that she had an unusual amount of company when the lights were on. Even her personal counselor mysteriously rearranged the scheduling of counseling sessions so they “just happened” to coincide with this woman’s bright light sessions! The lights lit up the lives of many people that winter.

Sadness, anxiety, irritability, and violence

I described this patient to emphasize that SAD is more than just a case of the blahs. Winter Depressions can be very, very severe. Even if not severe enough to warrant hospitalization as was the case for these two people, the symptoms can still be severe enough to disturb how you function and perhaps even interfere with your personal relationships. Mood certainly changes. Some people become sadder, to the point of experiencing real grief at times. Others become more anxious, and yet others become more irritable. At times the irritability can be so extreme that feelings of violence can erupt. This perhaps is one small part of the reason why the incidence of child abuse seems to increase during the dark months.

Other symptoms of seasonal depression

Physical activity decreases. The person feels very sedentary, and often sluggish. Physical activity, sometimes of almost any sort, seems to be just too much. On the other hand, appetite, and especially craving for carbohydrates (sugars or starches or alcohol) actually increases. Hypersomnia can develop: most people with SAD end up sleeping for very long hours (or wish they could, if life would allow it). In many ways, other than for the sometimes severe emotional symptoms, it is as if a person were hibernating during the cold, dark months.

How scientists discovered that light is the key to SAD

But can it be that we become more vulnerable to feelings of aloneness and other sad thoughts because of the decreasing hours of daylight and that it is the shorter day’s length which sets the stage for depression. Very probably so, think the scientists. In a now classical research paper authored by Norman Rosenthal and his colleagues, then at the National Institute of Mental Health (NIMH), SAD found its first description and received its name; and preliminary findings regarding a form of treatment with light was documented.

To make sure that this association between change in mood and amount of light was more than just mere coincidence, the next step was to supply light to see if it they could reverse the SAD mood. They used two different kinds of light, just to make sure the extra attention paid to the SAD patients wasn’t what helped resolve the depression. The dimmer, yellow light they used had no effect. However, the brighter light with a frequency spectrum more or less simulating the frequencies in sunlight, produced a marked change in mood in most (but not all) the patients who received that treatment. Their mood lightened, as it were, with the administration of light.

Since then, there has been quite an accumulation of evidence that it is indeed the decreasing length of the photo period (duration of the light part of a 24-hour period) which produces SAD in affected individuals.

About light therapy, depression and melatonin

According to my own research with just a handful of people, the first thing that changes with bright light therapy treatment is energy level. People begin to report feeling less sluggish and less fatigued, and shortly thereafter report having more energy. They also report that colors begin to seem brighter and the world stops seeming as faded as it did when they were in the depths of their SAD experience. And then, and only after all this has occurred, does the actual depression begin to lift. Working backwards, we began to think that perhaps the feeling of depression came only after energy levels became depleted, and the sleep need increased. For some reason, it was being unable to function well because of the feelings of lethargy which seems to have led to depression. And so this turns us once again to light, but with a different kind of question. What does light have to do with sleepiness and sluggishness? Well, that’s where melatonin may come in, if it comes in at all.

The master biological clock

Here is our current understanding. We are biological creatures and in general the human race depends a great deal upon being able to see. When primates and then humanity were evolving, before electricity was discovered, of course, but also before the discovery of fire, we could not see well when it was dark out. What better time, then, to sleep; to find a safe place to hole up in and get rest so one’s batteries could be recharged by sun-up for the next day’s hunting and gathering And so it became necessary to synchronize our internal biological clocks to the light-dark cycle in the geophysical world so that we’d be alert by daylight, and become sleepy as the sun began to set.

In recent years, a small cluster of brain cells (i.e. neurons) dubbed the suprachiasmatic nucleus (SCN), has been identified as the master biological clock’s probable site. Not surprisingly, in retrospect, one kind of information the SCN receives has to do with the amount of light coming in through the eyes. With this visual information, the SCN is in a position to coordinate the rhythms of our inner world with the rhythm of the light-dark cycle in the outer world.

Following a complicated pathway which involves a part of the nervous system called the Sympathetic Nervous System, the SCN eventually sends that information to a small gland at the base of the brain called the Pineal Gland. And it is melatonin, a hormone, that is produced by this gland. The amount of light seems to determine how much pineal melatonin is actually released from the pineal and secreted into the blood stream. The more light, the more release is suppressed. The less light, the more melatonin the blood carries. Light suppresses melatonin release.

What does that mean for the changing seasons?

During those seasons when the photoperiods are long, in the spring and summer, melatonin secretion is at its lowest since it can only be secreted at a significant rate during the relatively fewer hours of darkness. On the other hand, the closer we move toward the winter solstice, the fewer hours of light there are each day and, correspondingly, the longer the period of time each day when melatonin can be released into the blood stream.

The sleep-wake cycle: SAD, melatonin, body temperature

But, to sum things up, the most important association of melatonin to SAD seasonal depression, or Winter Depression, has to do with the relationship among blood levels of melatonin, body temperature and the sleep-wake cycle as related to the number of daylight hours. Melatonin is suppressed by daylight, so that in the spring and summer when the photoperiods are long, there is less time in a 24-hour period for melatonin to be secreted in the blood, and therefore less time for it to be involved in the lowering of body temperature. On the other hand, as we approach the winter solstice and the daylight hours grow shorter, melatonin has fewer hours of daylight to suppress it, and more hours when it can lower body temperature and possibly have some involvement in the triggering of sleep and perhaps sleepiness. In turn this may offer an explanation of why in some people — but not in others — their moods drop as the number of sunshine hours per day drop, and their moods come back up again as we move toward spring, away from the shortest day of the year.

Tips for avoiding the winter blahs, blues, or SAD

  • Pay attention to your moods and energy levels. If you realize that your spirits begin to sink at the end of the summer, take preemptive action. A good offense is better than after-the-fact defense.
  • Plan active events for yourself in advance of the fall.
  • Expose yourself to as much bright light as you can. If it is a sunny day, go outside as much as you can. If it is gray and overcast, use as much light indoors as you can.
  • Stay physically active, and begin your physical activity before the blahs get you.
  • Try to establish a mental set that will help you to enjoy the wintertime. It is going to happen, so gear yourself to get pleasure out of it.
  • By all means, if you feel yourself sinking and realize you are losing control, don’t feel ashamed or try to hide it. You are in good company. Many people feel this way. Seek competent professional help. What you learn from this season is something you can probably do for yourself in all the falls and winters to come.

Bright light therapy

  • Bright light therapy is the most established treatment for SAD.
  • Bright light therapy consists of looking at special broad spectrum bright lights from 1/2 to three hours a day, generally in the early morning hours. One should not stare directly into the lights because of possible eye damage.
  • A substantial amount of light is needed, which means the distance from the lights to your eyes needs to be monitored—close enough to give you the best amount of light, but distant enough so you don’t hurt your eyes.
  • The timing and length of the exposure per day are highly individual.
  • Bright light therapy is unlikely to help in certain situations because depressed mood is not always related to the decreasing number of daylight hours. Other possibilities are that you may have an ongoing depression, unlikely to be helped by bright light therapy. Your increasing irritability may be due to your spending more hours in the house cooped up, isolated from friends and neighbors. Or it might be due to keeping your dogs or cats in the house more than you do in the summertime and spring. If you are allergic to cats and dogs, doing this will produce allergy symptoms, which can produce poor sleep, which in turn can produce the impression of SAD–but such a mood change then will definitely not respond to bright light therapy. There are many other sources of depressed mood unrelated to light exposure.
  • If a few days of a light trial don’t make a difference in your depression, seek a different kind of help.


Comments to Dr. Lindsley:

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