Bipolar Disorder, Light, and Darkness

Table of Contents

Light and Darkness as Treatment (less meds!)

What you’re about to read gets to the heart of bipolar disorder. Bipolar has many causes – neurotransmitters, stress, inflammation – but the leading cause is circadian rhythm disruption. In other words, a broken biological clock.

How do we know that?

  1. The genes with the closest connection to bipolar are the same genes that program the biological clock (the are called the “clock genes”).
  2. Energy, sleep, motivation, appetite, concentration change throughout the day and are regulated by the biological clock. These are also the symptoms of bipolar disorder.
  3. People with bipolar disorder are more likely to be night owls.
  4. The melatonin system, which regulates the biological clock, does not respond as well to light and darkness in bipolar disorder.

There’s more. The sudden increase in sunlight in the spring is a common cause of mania, and antidepressants may even make people more vulnerable to that springtime flip by increasing the brain’s sensitivity to sunlight. On the other hand, several treatments for bipolar disorder repair the biological clock (especially lithium and social rhythm therapy, but also lurasidone/Latuda).Geoffroy, Calabrese

How to Set a Broken Clock

If your clock didn’t run right, you’d need to set it every day to keep it from getting too off track. Light and darkness are the main signals that set the biological clock, and there’s a natural therapy that stabilizes bipolar disorder by accentuating those signals. It involves extra light in the morning, and a strong dose of darkness in the evening. Jim Phelps, the founder of this website, helped develop the evening side of this therapy. Phelps, Burkhart

Here we’ll look at how light affects the brain, how lithium works on the same pathways, and how we can use this knowledge as part of standard bipolar treatment.

How Light Affects the Brain

You know about rods and cones, right? Those are the two kinds of light receptors in your eye, on your retina. But you didn’t know that there is another receptor for light in the eye (I’m guessing you don’t know, because until I came across this research, I didn’t know either).

Whereas the rods and cones send information to the visual cortex, this other light receptor sends its information to the biological clock. The nerve cables from these receptors don’t even go to the vision center at all. They go straight to the middle of your brain, to a region of the hypothalamus called the suprachiasmatic nucleus, which is the location of the biological clock for us humans. (That’s an oversimplification but the general idea is correct. For the minute details, light researchers would prefer an overview and series of articles in Nature 2005).

Everybody has a biological clock. It’s the gizmo that sets your biological rhythms every day — when you feel like eating, when you feel like sleeping, when you feel like getting up in the morning. The clock gets confused by airplane travel, causing jet lag. It regulates hundreds of chemical reactions all timed to match the natural cycle of days and nights in our environment.

Mental and physical functions peak at different times in the 24-hour cycled, but these same functions break down during mood disorders

Or what used to be our environment. Nowadays we’ve altered that environment in many ways, of course (nature is getting ready to get back at us, big time). One of the most significant changes is that we now have light when we used to have darkness.

Our morning light is much dimmer because we live indoors, and our evening darkness is more illuminated by blue light emitting diodes. These blue lights come from energy efficient bulbs and flat-screen computers, phones, and TVs. They are good for the environment because they use less energy, but they are bad for our brains because it’s the blue spectrum that tells our brain whether it’s morning or night.

Our brains were simply not built for this. There were built for a regular period of darkness within every 24 hours. Some people are not very affected by our artificially lit environment. But others, such as those with bipolar disorder, may suffer when they get too little, or too much. Actually, people who are prone to depression have this problem as well, just to a lesser degree (not by much though, only about 20-30% less).

From the Retina to the Biological Clock, and Then What?

Each morning, light sets the biological clock by shutting down melatonin, the hormone that makes us sleep. This reset is essential for everyone – not just people with mood disorders – because the average biological clock runs 15 minutes slow. In mood disorders, this morning reset is even more essential.

There’s a complex cascade of chemical reactions beyond shutting down melatonin that are involved in this reset. One of the enzymes in the process is affected by lithium. Here we find “ground zero” of our biological rhythms, the very center of the clock process, and there’s lithium right in the middle of it. Very interesting. If that’s enough to get you interested, have a look at the long story about how the clock works, including how lithium affects it.

Light is Central to Biological Rhythms, and so is Darkness

If light starts the clock every day, is it possible that darkness is a necessary ingredient as well? Look at the question this way: sleep deprivation can cause manic episodes. In part that’s too little sleep itself, but could part of the story be “too much light?” Generally when people are sleeping less and heading toward mania, they’re not hanging out in the dark. They’re up late at night in very well lit places, like casinos, roadways with bright car lights in their eyes, or in their office preparing the big talk that will secure their future millions, and so forth. They’re not sitting in some dark room. Is there any chance that being forced to stay in the dark during an emerging manic episode could actually turn them in the other direction? We’ll look at some evidence for that in just a moment.

Here’s another angle on light and dark. Suppose that the appearance of light every morning can reset your clock only when you’ve had enough darkness. Maybe the brain needs to see the contrast? What would happen if you didn’t get enough darkness? Maybe you’d lose your biological rhythm entirely. Your body wouldn’t know when to go to sleep and when to wake up. You’d be up in the middle of the night sometimes, for days in a row, backwards to real time. Then you might be so asleep during the real day you could hardly get out of bed; getting up in the morning would feel like getting up from sleep in the middle of the night does for the rest of us, ugh.

And finally, imagine that if your clock cuts loose from real time, losing even the 24-hour connection. Remember, the clock is not really a 24 hour machine in most people. Maybe you would lose your rhythm entirely so that you would fall asleep or turn wide awake at random times throughout the day. You’d have no idea where you were, in terms of body cycling, totally erratic. Extreme forms of “rapid cycling bipolar disorder” look just like this: No rhythm at all.

All of these lines of thought led a research team at the National Institute of Mental Health to wonder: Maybe the connection between the clock and external cues of light and darkness gets cut in rapid-cycling bipolar disorder. Maybe one way to treat rapid cycling would be to enforce evening darkness. The results of their test of this idea will be described in a moment.

What it Means for Treatment

There are two aspects of this story with major implications for the treatment of bipolar disorder. First, sleep and rhythm; and then, darkness and light.

Sleep and Rhythm

This one’s pretty simple. Everybody needs sleep. But people with bipolar disorder need to protect it even more. Sleep deprivation is associated with mania, mood swings, and depression. But perhaps even more important than the amount of sleep is the rhythm. Sleep needs to happen at the same time each day to keep your clock organized. Move it around too much and you may be setting yourself up for cycling – the ups and down of depressive, manic, and mixed-state symptoms that make life with bipolar disorder so miserable.

This is why shift work is such a problem in bipolar disorder. That wandering day/night schedule is about the worst kind of job schedule you could arrange. A close second might be an international job like pilot or flight attendant, changing time zones over and over again. Third worst would be graveyard shift work, unless you were extremely attentive to keeping your light exposure limited to your artificial day (using a dawn simulator to wake up and bright lights at work) and avoiding real daylight during your artificial night (heavy blinds and a sleep mask, for example).

So, the treatment bottom line. Keep regular hours of sleep, even on weekends. I know, it’s going to feel really stupid to be getting up at 6 am on a Saturday. You’ll probably have to conduct some personal tests to find out if this is really worth it. I’ll admit. Even if it’s theoretically a good idea for the long run, it’s going to be hard to keep it up unless you discover some shorter-term benefit as well. So keep some mood/energy/sleep records and see what you think.

Darkness and Light

If you have bipolar disorder you should very deliberately manage your exposure to light and darkness, especially darkness. This may be as important as regular sleep. Obviously the easiest way to arrange this would be to make sure you’re getting good quality darkness when you’re asleep. That means no nightlights (in one study, as little as 1/500th of midday sunlight, just 200 lux, was enough to disturb people’s melatonin, the sleep chemical in our brainHallam, and in another study a dim nightlight in the bedroom was enough to double the risk of depression over two years!).

That means don’t turn on the lights in the middle of the night if you get up to go to the bathroom (no hallway nightlight either). Don’t let early morning sun, in the summer, hit your closed eyelids (which means using, if you have to, a $3.50 sleep mask you can buy at the pharmacy. You’ll get used to it, and if you need light to use the restroom when you wake up in the middle of the night try these amber nightlights that won’t disturb the brain).

Here is a stunning case example to demonstrate how powerful Dark Therapy can be. A patient with severe rapid-cycling bipolar disorder who stopped cycling entirely — with no medications — just by carefully using very regular darkness (first 14 hrs a night, then within a few weeks, to stay well, only 10 hrs. a night). The graphs of his mood chart, before and after this treatment, are amazing. Please have a look, now or later, on my page about Dark Therapy.

No nightlights? You can use nightlights, actually, but they have to emit no blue light, as you’ll see in the next section.

Blue Alert

One particular wavelength of light is key to regulating the biological clock: blue light. Like the blue sky on a sunny day, blue light tells the brain “it’s morning time, wake up!” For an explanation of that research, see Why Blue Light is So Important.  So the last thing you’d want to be doing right before bed is looking at a blue light. Uh, oh. You can see it coming, can’t you: what color is the light from your television? How about from the computer screen you’re staring at right now? (not after 9 pm, is it? uh oh…)

The good news is this: You can significantly regulate your bipolar cycling by avoiding blue light at night. Here’s what you do:

  1. Avoid screens, and dim the lights, 1-2 hours before bed. Or wear the blue light filtering glasses described below 1-2 hours before bed.
  2. Sleep in a pitch dark room (if you need some nightlights to use the bathroom at night, or because you have a phobia of sleeping in the dark, there are amber-tinted brain-friendly nightlights on that link).

Some people are very susceptible to light; others are not. But if you’re one who is, these could be very important ideas to consider. One woman wrote, after reading this section:

“My daughter was very recently diagnosed with Bipolar II. I found your site while trying to understand what she is dealing with. When I read the article about darkness, I was amazed. My own sleep patterns are poor at best, so I decided to try some of your suggestions. I got away from the computer and the television two hours before retiring for the night. I bought an eye mask. In a little over a week, I have gone from waking up 3 to 5 times a night (and not falling back to sleep) and getting out of bed to awaking once to turn over and fall right back to sleep! I am at the point where I am telling anyone who will listen to me.”

Blue Light Filtering Glasses

Amber colored glasses that filter out blue light are getting trendy. Professional sports teams are wearing them (yes, they are performance enhancing, but legit). Celebrities from Miley Cyrus to Eddie Murphy are wearing them (J.Lo and Drew Barrymore have their own line). We don’t have our own line at PsychEducation, and we don’t make any money off these, but we’re increasingly convinced by the science behind them.

When you wear glasses that block blue light, your brain will think it’s in a pitch dark room. That means all the brain changes associated with darkness will kick into gear, starting with melatonin:

Melatonin rises between 9-10 pm if you’re wearing blue light blockers (“goggles”) or in a dark room (“dim light”), but if you’re in a brightly lit room the melatonin line is flat and barely rises at all (Kayumov, 2005)

The glasses change brain chemistry, and a 2016 study showed they can work like medication in bipolar disorder. The Norwegian researchers gave every patient with bipolar mania who came into the hospital a pair of glasses. Half of them got purple glasses (the placebo) and the other half got a pair that filtered blue light (the exact pair was from

Everyone put the glasses on at 6 pm, and the ones who got the blue light blockers were also instructed to sleep in a pitch dark room.

Within a week, they improved significantly (without any med changes!) compared to a placebo group. Dark therapy was pretty powerful in this study, clocking in with an large “effect size” (a measure of how much better it worked than placebo.Henriksen Here’s what else they found:

  1. The patients improved even though they didn’t sleep more. Actually, the ones who got dark therapy slept a little less than the placebo group.
  2. Although they didn’t sleep more, their sleep patterns became more regular, and their sleep quality improved (fewer night-time awakenings, deeper sleep, and less time tossing and turning in bed – what sleep scientists call “sleep efficiency).

The the full dark therapy protocol, read our six-step guide.

F.lux, a Computer Program to Shift Light

If light matters so much, and blue light matters most regarding mood and sleep — how about just taking out the blue at night automatically? Perfect. Someone built a program for this(the f.lux program), but unfortunately it does not take out enough blue. You can tell the difference, less blue, but still plenty of it. One reader described using a sepia theme on her e-reader, which is very much the same idea, the right idea. There is a blue-blocking filter to put over your computer screen or flat screen TV from They also make one for iPad mini, and iPhone.

Light Therapies: Dawn Simulators and Light Boxes

Finally, what about light? A regular rhythm of light in the morning would be good, by this analysis. How are you going to arrange that? Here we’ve left the realm of good solid research. So you don’t have to go buy one of these, just think about it: what about a “dawn simulator” for use when the sun is coming up long after your alarm? This is not a light box. It costs about $100. It’s just a light next to your bed that gradually comes on over about 45 minutes, while you’re asleep. Your regular bedside lamps can be part of it. The light will go through your eyelid and your brain will see it, even though your eyes are still closed (remember that special light receptor that connects straight to your biological clock; it works with eyelids closed!) You probably won’t need it in the summer; but depending on how far North you live, you might need it in the winter to have a more summer-like light exposure in the morning. (Here’s a list of dawn simulators by price and options).

Then there’s a true “light box”. These used to be big, suitcase-sized boxes, very bright, hard to tote around, and hard to situate near your breakfast table or bed (we’re talking morning light, right?). But now there’s a tiny one, about the size of your hand, the “little blue one”. If you’re not almost asleep already, and you’re interested in light as therapy, learn why blue light is so important. Consider a light box if you have repeated winter sag in mood and energy. Here’s the full story on light therapy.


Darkness is the unsung friend of people with bipolar disorder. Of all the things you could do for yourself to minimize the number of medications you take, and get the best possible outcome, this could be the easiest and it is almost certainly the safest (you can’t even twist your ankle with this approach!). Regularly timed, light-free darkness is your friend.

If you’re going to use light therapy, learn about the why blue light may be the key. Then learn about light therapy in general.

Now gloat, because you know a lot about light and dark that many people with bipolar disorder don’t!

If you would like to read a 4 page summary of blue light research by a health reporter, try this one: Holtzman (same link as above; moderately difficult but still plain English).

Related pages

So that you don’t have to chase them down if you skipped a link you’d now like to pursue, here are those which have been presented in this essay:

Technical Details 

In case someone needs the transmission data for the UVEX amber lenses, here ’tis:


And then you’d need to know that 550 nm light, where the graph line shoots up indicating that wavelength is “greener” is being transmitted, does not affect the circadian system much. Well, that’s not perfect. If the light is bright enough, it will, and if you are exposed long enough. But that green light is surely less powerful in this respect compared to blue light, as shown in this graph (I’m saving this information for myself. If you understand it, great. If not, well, you weren’t expected to show up here! You’re welcome of course. If necessary, you’ll figure out what these graphs mean:)


Reference: Lockley and colleagues, 2003.

Reference: Thapan, Arendt and Skene 2001

Artwork: The Starry Night, Vincent Van Gogh, 1889

(updated 11/2020)

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