What Is A SAD Lamp? Light Therapy For Seasonal Affective Disorder

Seasonal affective disorder (SAD), associated with seasonal depression or major depressive disorder with seasonal patterns, is a condition where people experience depression-related symptoms during a particular season. 

Most people with SAD experience symptoms in the autumn and winter, then see a remission from them in the spring and summer. A small proportion of people with SAD experience the opposite seasonal pattern with spring onset. 

SAD is a recurrent disorder, with most people’s symptoms returning at the same time each year. 

The direct cause of SAD and the reason why only some people are affected by the change in seasons isn’t known for sure. Experts believe several factors could be involved. 

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We make it easy for you to participate in a clinical trial for Seasonal affective disorder (SAD), and get access to the latest treatments not yet widely available - and be a part of finding a cure.

The circadian rhythm

SAD may result from a disruption to the circadian rhythm¹, which acts as a biological clock within the body.

The circadian rhythm is the 24-hour cycle that regulates numerous physiological processes, such as eating habits, sleep, body temperature, and hormone release. 

The circadian rhythm is governed by an area in the brain that receives information and messages from external cues, the most important of which is light exposure. When the days grow shorter in autumn, the circadian rhythm becomes out of sync with the clock time and sleep-wake cycle. This is known as the ‘phase-shift hypothesis,’ and it’s similar to what happens when you have jet lag. 

Vulnerability to phase shifting of the circadian rhythm in response to seasonal changes may be influenced by genetics. A pulse of bright morning light is thought to realign the circadian rhythm with the sleep-wake cycle. 


Serotonin is an important hormone, or chemical messenger, that helps regulate mood by sending messages between nerve cells. However, when too much serotonin is reabsorbed into the cell that produced it, it’s unable to send messages, and the hormone can’t effectively carry out its function. 

Some experts believe that people with SAD have lower levels of serotonin during the times of the year with fewer hours of sunlight. This is believed to be due to greater reabsorption of serotonin² during the autumn and winter months when light levels are lower. 

One factor impacting this is that vitamin D levels, influenced by light exposure, trigger serotonin production. Furthermore, some people may be vulnerable to lower light conditions that negatively impact serotonin receptor activity.

Melatonin is another hormone produced in the brain. It helps regulate the circadian rhythm and the sleep-wake cycle by promoting sleep and sending information to the brain about night length. The production of melatonin is stimulated by darkness; the brain generally starts releasing melatonin about 1 to 2 hours before you fall asleep in the evening. 

A change in seasons is thought to disrupt the balance of melatonin³, therefore influencing sleep and mood. 

What is light therapy?

Light therapy, also known as ‘phototherapy’ or ‘bright light therapy,’ is an evidence-based treatment for several mental health conditions, including SAD. 

Light therapy uses artificial light to improve mood and relieve depressive symptoms by affecting the body’s chemical messengers associated with mood and sleep.

SAD lamps

SAD lamps are one example of light therapy used for treating SAD.

Sometimes known as ‘lightboxes’ or ‘sun lamps’, they consist of a flat screen or a box that exposes your eyes to an artificial, bright white light that replicates natural daylight. Since winter SAD is thought to be triggered by reduced hours of sunlight, the artificial light provided by SAD lamps can help reduce depressive symptoms and improve mood. 

However, its purpose is not only to provide more total exposure to light. Light therapy also helps to repair the phase shift. 

The light passes through your eyes and stimulates an area of the brain that regulates the circadian rhythm. Consistent exposure to light in the mornings promotes entrainment, or synchronization of your biological clock, regulating your sleep-wake cycle and hormone production. 

Light therapy may also increase levels of available serotonin and halt the production of melatonin, helping to regulate its release.

How do you use a SAD lamp?

SAD lamps are relatively straightforward to use and don’t require a lot of work. However, for a SAD lamp to be effective, you need to follow some important instructions. 

Position of the lamp

You should place the lamp about 12–24 inches (30–61cm) from your face. It should be positioned at a downward angle, about 30 degrees from your line of gaze. 

You should not stare directly into the light, as this could damage your eyes. 

Length of therapy sessions

Each session of light therapy with a SAD lamp should be around 30 minutes, although it can be increased up to 60 minutes⁴ if needed. This is assuming that the standard treatment using 10,000 lux is applied.

You should not exceed the time recommended by the lamp manufacturer or by your doctor. 

If you do experience mild side effects from light therapy, you may need to start with shorter sessions and gradually increase them to 30 minutes over time. 

Frequency of use

Light therapy sessions should be consistent and regular. You should try to incorporate light therapy into your daily routine. It might be helpful to set aside a specific time to use your SAD lamp every day. You should aim to use it at the same time every day for the best results.

It’s okay to take a couple of days off occasionally. However, stopping light therapy too early can cause SAD symptoms to return². Even if you feel better during light therapy, it’s important to keep going for the entire treatment time. 

When to begin and end light therapy

There is no harm in trying light therapy, even if you aren’t sure whether you have SAD. It’s best to begin the treatment before you typically get SAD symptoms.

For example, this could be: 

  • Two to four weeks before your predicted recurrence of symptoms 

  • Early autumn, when the daily hours of sunlight begin to reduce 

You should continue light therapy for several weeks throughout the winter and early spring until natural daily sunlight levels increase again. 

Some experts recommend continuing light therapy for a further two weeks after symptoms end. For example, a person may begin light therapy on 1 October and end it on 1 April.

The time of day

Evidence suggests that SAD lamps are most effective in the early hours of the morning² and preferably as soon as possible after you wake up. A good rule is to aim for some time before 10AM. 

Although some people may benefit from using light therapy throughout the day, using a SAD lamp in the evening⁵ is not recommended. Doing so could interfere with your sleep, cause insomnia, and further disrupt your sleep-wake cycle. In turn, this could worsen your SAD symptoms. 

What to do during light therapy

Most forms of light therapy, including SAD lamps, can be carried out at home without having to go to a treatment center. 

One benefit of light therapy is that you can do many everyday tasks while using the lamp. You could read, watch TV, eat breakfast, or work.

As long as your eyes remain open for the duration of the treatment and the light can indirectly reach them, you can do almost anything you like to occupy yourself. 

One study even suggests the potential effect of light therapy on mood when combined with exercise⁶, such as using a treadmill or an indoor stationary bike. 

You should not wear sunglasses during light therapy as it’s important for the light to reach your retina. 

Who should use SAD lamps?

SAD lamps are available for purchase by anyone and have straightforward instructions with minimal risks. If you decide to use one yourself at home, monitor your symptoms for potential changes and talk to a healthcare professional if you have any concerns. 

If you notice yourself feeling low or sad during the winter months, you may indeed benefit from a SAD lamp. It is also a helpful year-round treatment for people who experience insomnia. 

As for formal regulations, the Agency for Health Care Policy and Research (AHCPR) states that the following principles should be followed when considering light therapy:

SAD lamps should be recommended and administered by a healthcare professional who has experience and training in light therapy and thinks it’s suitable for the patient living with SAD. 

SAD lamps can be used as a first-line treatment for SAD in the following conditions: 

  • There are medical reasons for avoiding antidepressants 

  • The patient shows a positive response to light therapy

  • The patient doesn’t experience negative effects and doesn’t have a history of side effects to using a SAD lamp 

  • The patient requests light therapy and has no conditions precluding its use

  • The patient isn’t severely suicidal

SAD lamps can also be a second line of treatment for SAD if medication has failed. Many people use SAD lamps for winter blues, which is when your mood is low in winter but not as low as with clinical depression.

What are the benefits of using SAD lamps?

Studies have found that people experience positive outcomes around 80%⁷ of the time when they try morning light therapy. 

SAD lamps can reduce SAD symptoms and improve your mood. In one study² of patients with SAD, 61% of the participants experienced a reduction in symptoms and/or remission of SAD after just four weeks of regular bright light therapy. 

Light therapy targets some of the proposed causes of SAD. 

  • When done in the morning, light therapy is believed to correct the phase delay between the circadian rhythm, the clock time, and the sleep-wake cycle.

  • Light therapy may increase the amount of serotonin in the space between nerve cells in the brain. Having more serotonin in this area allows messages to be sent between nerve cells more efficiently, which in turn helps regulate mood. 

  • Since light inhibits melatonin production, SAD lamps could help you feel more alert and improve your mood.

Light therapy works quickly

Light therapy is relatively fast-acting. Some people start to notice the positive effects of light therapy after only a few days of treatment. 

A couple of smaller studies⁸ have shown that after 20 to 40 minutes of light therapy with a lightbox, some people with SAD demonstrate an early and instant reduction in their self-reported depression scores.

However, it can take two to three weeks to begin to feel the effects in some cases. 

Light therapy isn’t effective for everyone. If you haven’t experienced any sort of positive response after three weeks of regular use, you could consider alternative treatment options rather than waiting for the light therapy to work.

Light therapy compared to other treatments

Light therapy can also help increase the effectiveness of other treatments used for SAD, such as antidepressants and psychotherapy. If you are on antidepressants, you may be able to reduce your dosage, which could, in turn, reduce or prevent negative side effects from that medication. 

A combination of light therapy and antidepressants is often recommended for people with severe SAD. What’s more, some people with SAD may tolerate light therapy better than antidepressant medications.

In general, the overall effectiveness of antidepressants and light therapy for SAD has been shown to be similar⁹.

However, compared to antidepressants, light therapy may⁹: 

  • Have a quicker response 

  • Result in depression scores being lower after one week

  • Have fewer negative side effects

Always speak to your doctor before making any treatment changes. 

The safety of light therapy

SAD lamps filter out ultraviolet (UV) light, so the light will not damage your eyes or skin. SAD lamps are safe for most people. However, there are still some risks that you should be aware of. 

Side effects

Some people experience minor side effects from using SAD lamps. These include:

  • Eyestrain 

  • Headache

  • Nausea 

  • Fatigue due to changes in your sleep-wake patterns 

  • Photophobia

  • Insomnia (difficulty sleeping, when used in the evening 

  • Irritability, anxiety, and agitation

  • Eye irritation and dryness 

These side effects are usually temporary and should resolve on their own as you continue to use the SAD lamp. In fact, very few people¹⁰ need to discontinue light therapy after experiencing these side effects. 

To reduce side effects, you could make minor adjustments to the treatment by: 

  • Increasing the distance you sit from the lamp 

  • Reducing the lamp’s light intensity

  • Taking a break during a session

  • Reducing the total time of each daily session

  • Changing the time of day you use a SAD lamp

  • Limiting your screen time while using your SAD lamp

If symptoms don’t resolve after a couple of weeks, see your doctor for advice. 

If you have summer-pattern seasonal depression, SAD lamps are not a good treatment choice. This is because summer SAD can be triggered by the increased hours of sunlight per day. In fact, for people with summer SAD, it’s recommended to limit your exposure to sunlight. 

Risks with pre-existing medical conditions

You should take caution with SAD lamps in the following circumstances:

Certain eye conditions

Some eye conditions make your eyes sensitive to light, including macular degeneration, glaucoma, and retinopathy.

If you have one of these eye conditions, you should speak to your ophthalmologist (a doctor who specializes in eye disorders) before using a SAD lamp because the doctor may wish to monitor your eyes.

Bipolar disorder

People with bipolar disorder may experience hypomania or mania when using light therapy.

Physical conditions

Some conditions can also increase your sensitivity to light, such as systemic lupus erythematosus. Diabetes can damage the retina and make your eyes more vulnerable to phototoxicity.

Some medications

Certain medications such as lithium, tetracycline, tricyclic antidepressants, anti-inflammatories, the herbal supplement St John’s Wort, and antibiotics can increase your sensitivity to light.

SAD lamps are not a cure for SAD

It’s important to understand that light therapy is unlikely to cure SAD fully and should be viewed as an ongoing form of treatment.

Its effects are relatively short-term, and most studies show that SAD lamps don’t provide long-lasting effects that could prevent SAD from recurring the following year.

SAD lamps should also not replace medication such as antidepressants if you have been prescribed them.

How to choose the right SAD lamp

Light intensity

Lux is a measure of the output of light (lumens) that reaches the eye in a given area.

It’s believed that 10,000 lux is the most effective light intensity for treating SAD. This is much brighter than a standard lamp you might use in your home. For reference:

  • A well-lit room is around 250 lux

  • A cloudy day can reach up to 5000 lux

  • A bright summer day can reach up to 100,000 lux

If your SAD lamp has a different light intensity, the distance of the lamp from your face and the duration of the light therapy session should be adjusted accordingly. For example, a 2,500-lux lamp requires daily sessions of 1 to 2 hours to have the same effect as a higher intensity lamp.

If you choose a SAD lamp with lower light intensity, you may need to wake up earlier than usual so that you have time to complete a full session. This could be unhelpful when you’re trying to normalize your sleep-wake cycle and repair the circadian phase delay.

The wavelength spectrum

You shouldn’t use a SAD lamp that’s designed to treat skin disorders. These are not effective for SAD, and more importantly, they often emit UV light, which can damage your eyes and skin and can lead to skin cancer. Although SAD lamps and those used for treating skin disorders may look similar, they serve a very different purpose.

A lamp made for treating SAD should have a diffusion screen that filters the UV light. It will be clearly labeled by the manufacturer for its intended use.

Instead of UV light, make sure the SAD lamp is either full-spectrum visible light or cool-white fluorescent light.

Clinically tested or reviewed

SAD lamps are not regulated by the US Food and Drug Administration (FDA), so it’s important to do your research, seek advice from your doctor, and read authentic reviews before you purchase a SAD lamp. 

There are no official certification or regulation standards, but many widely available lamps have been verified as high quality. 

Size and style of the SAD lamp

SAD lamps can vary in their design. 

The size and style you choose are up to your personal preference and your budget. SAD lamps can be purchased as floor lamps, desk lamps, and even small portable lamps suitable for travel. Some have adjustable brightness settings. 

Make sure to always read and follow the manufacturer's instructions provided. You must know what to expect to ensure that your light therapy will be safe and effective.

Are there other types of light therapy?

There are several other forms of light therapy, most of which are less effective than SAD lamps. However, if you find that SAD lamps are not working for you, one of these options may be suitable.

Actual sunlight

If you live somewhere with longer days and available sunlight, you can merely opt to go for a walk outside in the morning. Sunlight is as effective (or more effective) than a SAD lamp, but this is not a viable option for many people in cooler climates. 

Dawn simulators

A dawn simulator is a lighting device that mimics a natural sunrise. The light gradually increases from darkness to around 250 lux over 1.5 hours in the early morning while you’re still asleep. When you wake up, the gentle light surrounding you resembles dawn. 

Studies have shown that dawn simulators have an antidepressant effect, and, like SAD lamps, they can help normalize sleep-wake cycles and reduce SAD symptoms. Some people prefer dawn simulators to SAD lamps as they require less energy and commitment since they work while the person is asleep. 

Light visors

Light visors are head-mounted portable lighting. Like dawn simulators, they are often seen as easier to use than SAD lamps. They’re thought to demonstrate phase shifting of the circadian rhythm. However, some studies show they’re no more effective than exposure to dim light¹⁰.

How can you get a SAD lamp?

SAD lamps don’t require a prescription, so you don’t need to see a doctor. However, it’s recommended to do so. Your doctor can talk through your medical history to ensure a SAD lamp is safe and effective for you. This can protect your health and save you a lot of money if it turns out that a better treatment is available for your situation. 

SAD lamps can be purchased in retail stores and online and generally range from US$40 to $500. You don’t need an expensive one to get the most benefit. 

The lowdown

Light therapy is an easy, safe, and effective treatment for depression related to SAD. In recent years, it’s become the first line of treatment for SAD. 

SAD lamps are the most common form of light therapy. They help realign your sleep-wake cycle and your body’s internal clock (your circadian rhythm). Make sure that you follow all recommendations for choosing a SAD lamp and the instructions by the manufacturer or your doctor so you can have the safest and most effective outcome.

Have you considered clinical trials for Seasonal affective disorder (SAD)?

We make it easy for you to participate in a clinical trial for Seasonal affective disorder (SAD), and get access to the latest treatments not yet widely available - and be a part of finding a cure.

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