Using light therapy for seasonal affective disorder (SAD)

Seasonal depression, also called seasonal affective disorder (SAD) affects roughly 5% of people every year (most frequently, during the darker days of winter when the lack of light affects our circadian rhythm). SAD is more than just being annoyed about shorter, darker days. It happens when the levels of certain chemicals in your brain like melatonin and serotonin are out of balance, leading to symptoms like low energy, excessive sleeping and eating, sadness, and loss of interest in normal activities (APA, 2020).

Light therapy in the form of SAD lamps and light boxes mimic sunlight to help your body adjust its circadian rhythm, raise serotonin levels, and regulate melatonin. These devices are often used as a first-line treatment for mild to moderate SAD (Avery, 2020; Maruani, 2019).

Since its first use in the mid-1980s, light therapy has been refined and improved. Nowadays, there are countless SAD lamps and light boxes you can choose from, and we’ll help you with that in this article (Campbell, 2017; Rosenthal, 1984).

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There are two types of SAD lamps that can be used on their own or in combination: bright light therapy devices and dawn simulation lamps.

You can purchase SAD lamps at medical supply stores, pharmacies like CVS, and online retailers like Amazon. As you can imagine, there’s no shortage of options when it comes to selecting a lamp, which can make it hard to make the right choice.

Here are some science-based recommendations around what to look for in a light therapy device, as well as how to use them.

Bright light therapy devices

Bright-light therapy (BLT) involves sitting in front of a box that uses fluorescent tube lights or LED light bulbs and a diffusing screen or reflector to deliver bright white light—equal to the light that meets your eye outside on a bright day.

Bright-light therapy has been shown to be effective and to work safely and quickly—typically within a week. Multiple studies have shown that, on average, 67% of people with milder cases of SAD respond positively to bright-light therapy, as do around 40% of people with severe cases (Maruani, 2019).

Experts recommend using commercially available light-therapy boxes rather than constructing your own, given the need for precise measurement of lux. Lux tells you how bright something is; higher lux equals higher brightness. For example, 500 lux is the brightness of indoor office lighting, while 100,000 lux is direct sunlight in the middle of a bright, sunny day (Avery, 2020).

Here are some key aspects of bright light therapy and things to look for when buying a BLT product (Avery, 2020; University of British Columbia, n.d.).

• Brightness: 10,000 lux (approximating daylight) is the common recommendation (Terman, 2006).

• Light source: Don’t select a lamp that uses ultraviolet or UV light. These lamps are made to treat skin conditions like psoriasis but should be avoided in bright light therapy since UV light can damage the eyes (Pail, 2011)

• When to use it: Ideally, start as soon as possible after you wake up in the morning.

• How to use it: You’ll usually want to face the light from 16–30 inches away, based on the manufacturer’s directions. The light should at least be in your peripheral vision. While it’s okay to glance at the light, do not stare directly into the light. As long as the light is shining on your face, you can do other things like working at your desk.

• Duration: Sessions are usually 20 to 30 minutes per day for a 10,000-lux setup. The lower the lux, the longer you have to sit in front of the lamp. For example, you need two hours of exposure when using a 2500 lux light box to achieve the same benefit of 10,000 lux for 30 minutes.

• Frequency: Once a day, and a consistent, daily routine is important.

Dawn-simulation devices

In this variation, less intense light emanates from a device in the room before a person wakes up, simulating sunrise. Dawn-simulation lamps are sometimes used in tandem with bright light products.

Research suggests that dawn simulation may be at least as effective as bright light therapy, with the benefit of working like a natural alarm clock. One study found that dawn simulation induced remission (total resolution of SAD symptoms) in more people than bright light therapy or placebo (Avery, 2001). Another study compared bright light therapy and dawn-simulation devices. Each reduced depression symptoms in mild to moderate cases of SAD, but among people with severe depression, bright light therapy worked better (Danilenko, 2015).

Here are some key aspects of dawn-simulation devices and things to look for when buying one (Avery, 2020; Terman, 2006):

• Brightness: 250 lux at the peak, which is much less intense white light than bright light therapy.

• Light source: Beside the bed, 36 inches from the pillow.

• When to use it: During the final hours of sleep. Dawn-simulation therapy devices are set ahead of time to deliver a dose of modest morning light automatically.

• How to use it: Their big advantage is they don’t require you to sit in front of a device while you are awake. 

• Duration: Anywhere from 30 to 90 minutes before your normal wake-up time. Light exposure ends with your wake-up time.

• Frequency: Daily

Bright-light therapy is generally safe, and side effects are typically mild and rare. Eye irritation, headache, nausea, have been reported, but many of these symptoms tend to go away within a few days. If you feel agitated and irritable after light therapy, it’s best to reach out to a healthcare provider (Maruani, 2019; University of British Columbia, n.d.).

If you have retinal disease, macular degeneration, or diabetes, or if you have any concerns about the effects on your health, see a doctor before you try bright-light therapy (University of British Columbia, n.d.).

SAD can make life extremely difficult, particularly during the winter months. Speaking with a mental health professional can help you find the right treatment for you. Light therapy may be part of the solution, as it offers a potential remedy for SAD that sometimes works more quickly than antidepressants. Additional strategies to treat SAD include increasing physical activity, improving diet, and spending more time outside in bright, natural light.

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Current version

December 01, 2021

Written by

Robert Roy Britt

Fact checked by

Felix Gussone, MD

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About the medical reviewer

Felix Gussone, MD, Ro

Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.