Dark Therapy

Mood disorders are caused in part by a breakdown of the body’s internal clock. That clock is set by light and darkness. In bipolar disorder, morning light improves depression and evening darkness calms agitated moods like mania and mixed states.

A Famous Case

Mr. J went in and out of mania and depression for many years. His condition was so untreatable that he went to the National Institutes of Health for help. Researchers there had recently discovered that insomnia improved when people stayed in a pitch dark room throughout the evening. Sleep and are tightly linked, so they tried this therapy on Mr. J.

Every night, he stayed in total darkness for 14 hours, from 6 pm to 8 am. His mood improved quickly, and they eased the dark schedule from 14 to 10 hours of darkness per night (10 pm to 8 am). Within a few weeks, he was fully recovered.

Since then, a dozen studies have confirmed the benefits of dark therapy for insomnia, shift work, and bipolar disorder. A note of caution on that. Most people with bipolar disorder do not feel they sleep better with dark therapy, In the studies, it didn’t help them fall asleep, but their sleep did get deeper and more regular. Dark therapy improves manic moods even if you’re still awake all night while doing it.

Dark Therapy the Easy Way

The original dark therapy required a pitch dark room. An easier approach is to use amber, blue-light blocking glasses. It’s the blue wavelength that causes mental health problems when it’s too intense in the evening.

There’s a special receptor in the eye that detects blue light (melanopsin), and the brain uses that signal to set the biological clock. Blue light is helpful in the morning, but too much of it at night is bad for the brain.

In a landmark study from 2016, people who wore these glasses from 6pm to 8am (except when in bed in the dark) had a significant improvement in mania within a week. The patients who improved did not actually sleep more, but their sleep did become more regular. It’s as if the glasses allowed their brains to get some of the benefits of sleep without actually sleeping.

Blue Blocking Glasses

As news of their sleep-enhancing qualities has spread, blue light blockers have become very popular. Celebrities endorse them, and sports teams wear them to improve next-day performance. One book touts them for weight loss (it is true – a dark bedroom improves metabolism).

Unfortunately, that popularity has brought a tide of poor quality products. For this to work, you need glasses that block at least 90% of blue light. The models below past that mark in testing by Consumer Reports or proved their merits in clinical trials.

How to Start Dark Therapy

If your symptoms are severe, start with a full 14 hours (6 p.m. to 8 a.m.) of darkness, and transition to 10 hours (10 p.m. to 8 a.m.) as you start to recover. When transitioning, adjust by 1 hour every two nights (e.g. darkness at 7 p.m. for two nights, then 8 p.m. for two nights, until you reach 10 p.m.). If lowering the time spent in darkness makes your symptoms worse, just back-track and increase your dark-exposure by an hour. For milder symptoms, you can start with 10 hours of darkness (wear the glasses 2 hours before bed and then sleep in a pitch dark room for 8 hours).

It’s best to keep the lights down low while wearing blue blockers. Don’t drive with them on. The glasses are not comfortable to sleep with, so you’ll need to create total darkness in the bedroom. Try black-out curtains, a windowless room, a sleep mask, or more tips here.

Do not use dark therapy during the day. Remember the idea is to set your clock, and daytime light helps with that.

Dark Therapy in 6 Steps

1. Evening. At 6 pm, put on blue-light blocking glasses. Wear them until ready for bed, and keep the lights down as low as you’re comfortable with. Don’t take the glasses off unless you’re in a pitch dark room. Pitch dark means you can’t see your hand in front of your face.

2. Sleep. Get your bedroom pitch dark with these steps. When ready for bed, lay down in the pitch dark room and take the glasses off.

3. Overnight. If you get up at night and turn the lights on, make sure to wear the glasses. Otherwise remain in your pitch dark bedroom throughout the night, whether asleep or not.

4. Morning. At 8 am, turn on the lights, or use a dawn simulator to wake up. Don’t wear the glasses during the day.

5. As you improve. Once your symptoms improve, slowly put the glasses on later in evening, moving the start time up by 1 hour every two days until you’re wearing them 2 hours before bed.

6. Prevention. Once recovered, keep wearing the glasses 2 hours before bed and sleep in a pitch dark room. That will improve overall health (less cancer, weight gain, and diabetes) and prevents bipolar. It will also deepen your sleep quality so you’ll feel better the next day.

Troubleshooting. If you can’t get the room pitch dark, use a black sleep mask. If you can’t tolerate pitch darkness, use a low-blue night light. If you’re used to having the TV on in the bedroom, try music or podcasts instead (or search for the top sleep-inducing track: Weightless by Marconi Union). Don’t expect this therapy to make you sleep. Dark Therapy gives your brain many of the healing properties of sleep even if you’re wide awake all night.

Bottom Line. During Dark Therapy, you’ll need to be in virtual darkness (with blue light blocking glasses) or pitch darkness for the entire evening.

Other Health Benefits

Reducing blue light in the evening causes weight loss and lowers the risk of cancer, diabetes, and heart and eye disease.

Other Ways to Lower Blue Light

What if you can’t sleep without light? Try a low-blue nightlight:

• Click Lighting Products at LowBlueLights.com
• GE SleepLite
• Beams MB720A Night Light
• Bulb: Harth Sleep-Shift Sleep Ready Light

For reading in bed, try the Harth Blue Light Blocking Book Light.

There are also apps that reduce blue light from computers and phones, like F.Lux, Nightshift Mode, and Twilight. These do some good, but they don’t filter enough blue light on their own. Most blue light comes from energy efficient bulbs, and these apps won’t reduce that.

Side effects

Blue light glasses can cause vivid dreams and headaches. They can improve depression if worn 2 hours before bedtime, but they can cause depression if put on too early (before 6 pm).

–Chris Aiken, MD, Updated 5/16/2024

Key points

• Dark therapy improves agitated moods like mania and mixed states.
• It involves staying in a pitch dark room, or wearing blue light blocking glasses, from 6 pm to 8 am each night.
• Dark therapy can deepen sleep, but it works even if you aren’t able to sleep.

Dark therapy deepens sleep, but it improves agitated moods even if people are unable to sleep and up all night while doing dark therapy.

Can’t stand the dark? With dark therapy, the less light the better, but low-blue nightlights are good options if total darkness isn’t feasible.

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