How Bright Light Therapy Helps with Low Mood, Sleep Problems and Jet Lag
By Daniel F. Kripke, M.D.
Last Revised November 2019
Good Sleep Habits
Since much of this book has been about using bright light to sleep better, it may surprise you that I think many people try to sleep too much. We are all familiar with the unpleasant feeling of having slept too little, but many of us have not thought about the possible harm of trying to sleep too much.
You may have heard somewhere that eight hours of sleep per night is recommended for optimal health. I do not agree with recommending eight hours or more of sleep for adults. In our studies in San Diego, the average adult is actually asleep only between 6 and 6.5 hours a night. Moreover, The Cancer Prevention Study II showed that people who report sleep of 6.5 to 7.5 hours live a bit longer than people who report sleep of eight hours or more. The shorter sleepers lived longer! Even some people who slept as little as 3.5 hours lived longer than those who slept eight hours or more. Certainly, if you get only 6.5 or 7 hours of sleep a night and are not too sleepy in the day, you are probably sleeping enough. A recent systematic review found that long sleep was significantly associated with cardiovascular mortality but short sleep was not. Another recent paper found that sleep of eight hours or more predicts future Alzheimer’s Disease. My opinion of the healthiest sleep duration is based on my own studies of data from over two million research participants. Additional studies with further millions of participants have confirmed my viewpoint. If somebody claims to have evidence that you need eight hours sleep for health, ask them how many million volunteers they have studied.
Incidentally, when we record sleep in people above age 60, the amount of brain wave sleep is often about an hour less than the person reports on a questionnaire. In a study of elderly volunteers for the Women’s Health Initiative, we found that women whose recorded sleep was 5 to 6.5 hours lived the longest.
Studies show that in the range that most Americans sleep (which is reported to be six, seven, or eight hours or so), there are few discernable differences between people. This may surprise you, but people who sleep six hours seem to be about as happy as people who sleep eight hours or more. Moreover, people who sleep six hours get just as much work done and are more likely to be employed than people who sleep eight hours or more. There may be some tendency for people with the shortest sleep times (five or six hours) to be outgoing and energetic, whereas people with the longest sleep times (nine or ten hours) seem to be more introverted, more imaginative, and (on average) more depressed. Notice the surprise! People who sleep a bit less than average may be less depressed!
Indeed, hospital studies of depressed patients show something very surprising. When depressed patients are kept awake all night (or at least for the second half of the night, e.g., after 2 am), they surprisingly feel less depressed the following day. The sleep loss helps depressed mood. This was part of the wake treatment which is now a part of chronotherapeutics and the triple treatment of depression. Moreover, after the wake therapy, taking a nap makes depressive symptoms recur. Wake therapy would be a very popular treatment for depression except for one problem: people with depression who stay up during the night do get sleepy, and after they sleep soundly the next night, the low mood usually relapses (unless bright light is used). Evidently, although it is true that people who are getting depressed have poor sleep, it is not true that getting more sleep helps depression. Often it is quite the opposite.
For these reasons, most depressed people should not struggle to get more sleep. People may often improve their moods by getting up a bit earlier.
There is another factor. Spending more time than necessary in bed – as you might expect – causes people trouble with falling asleep and makes them more likely to awaken while in bed. Sometimes, the frustration of lying in bed awake adds to the problem, and it builds on itself, getting worse and worse. The more time the person spends in bed trying to get more sleep, the more trouble develops in falling asleep and the more the person awakens in the night. Surprisingly, it seems that spending too long in bed might be a major cause of sleep trouble among both elderly and depressed people. Fortunately, there is an easy solution.
People who are spending a lot of time in bed lying awake should spend less time in bed. This means either going to bed later or getting up earlier. Getting up by a regular time seems to be important, so trouble falling asleep should not persuade you to sleep late. The less time you spend in bed, the sleepier you will be the next evening. Think about it. If you spend less time in bed, you will surely tend to fall asleep more easily and sleep more soundly in the future. Moreover, the less time you spend in bed, the more you will gradually restore the habit of falling asleep quickly after going to bed, and the more you improve the habit of sleeping soundly. Some doctors would recommend that you should not spend more time in bed than you actually sleep. If you think you only sleep as little as six hours a night, perhaps you should spend only six hours in bed until you are sleeping all six hours. Then you can try increasing time-in-bed about 15 min., e.g., to six hours and 15 minutes. You can gradually increase your time in bed on a weekly basis until you are no longer sleepy enough to sleep at least 85% of your time in bed. Once you are sleeping only 85%, that may be the longest time in bed that you should allow yourself. One warning: although this kind of sleep restriction is now a standard element of the cognitive-behavioral treatment of insomnia, it does produce more daytime sleepiness in the first few weeks of treatment, so caution is necessary when driving.
Most sleep experts also recommend that whatever bedtime you allow yourself, you should not go to bed if you do not feel sleepy. Moreover, if you awaken at night and no longer feel sleepy, get out of bed, and do not go back until you are sleepy again and expect to fall asleep. Even after being up during the night, you should get out of bed by your regular awakening time, because sleeping late tends to make the problem worse. Getting out of bed when you are not sleepy makes you sleepier the next night and helps maintain good sleep habits.
Almost all of us have stayed up entirely for a night or two, so we know that nothing terrible happens to us. Many of the patients I talk with say that they have slept only a few hours a night for years, and yet they are somehow terrified that losing sleep will harm them. Probably not. Remember that if anything, the short sleepers tend to live longer and often are less depressed. If you are willing to stay out of bed and amuse yourself somewhere else when you are not sleepy, soon you will stop worrying about sleep. If you lose a whole night’s sleep or part of a night, so what? It probably will be a minor problem at most, as long as you do not worry about it. When you do go to bed (because you are finally sleepy), you will have restored your confidence that you are likely to fall asleep, so the long-term problem resolves.
It is extremely common that depression, advanced sleep phase, or delayed sleep phase lead to poor sleep habits, and then the poor sleep habits become part of the problem. For this reason, it is important to observe good sleep habits when you are using bright light, in order to restore your sleep confidence. It has been shown specifically that sleep restriction can reduce depression.
If bad sleep habits are part of your problem, commercial websites such as CBTforInsomnia.com and SHUTi can give you more detailed pointers about how to correct sleep habits. (As this is written, the availability of SHUTi is in transition, so it would be best to look for it on the web when you need it.) DO NOT USE THE POPULAR SLEEPING PILLS: they are too dangerous. For more information about the risks of sleeping pills, you can look at my free website, The Dark Side of Sleeping Pills. Some of this information about good sleep habits is explained in more detail there.
Endnote for Chapter 8
87. Epstein DR, Sidani S, Bootzin RR, Belyea MJ. Dismantling multicomponent behavioral treatment for insomnia in older adults: a randomized controlled trial. Sleep. 2012;35(6):797-805; Kalmbach DA, Cheng P, Arnedt JT, et al. Treating insomnia improves depression, maladaptive thinking, and hyperarousal in postmenopausal women: comparing cognitive-behavioral therapy for insomnia (CBTI), sleep restriction therapy, and sleep hygiene education. Sleep Med 2018;55:124-34.[return]
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Brighten Your Life, in all its formats, including this ebook, copyright ©1997-2019 by Daniel F. Kripke, M.D. All rights reserved.