UV Lights For Seasonal Depression: Do They Work?

Seasonal depression¹, formally referred to as seasonal affective disorder (SAD), can be extremely debilitating. It occurs when an individual has periodic depressive episodes that follow seasonal patterns. 

These depressive periods often occur most frequently in the winter months. Common symptoms include low mood, changes in appetite, sleep disturbance, and general irritability. 

This disorder can also include bipolar variations², where an individual alternates between depression in certain seasons and mania during the rest of the year. 

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.

UV lights and SAD

One commonly posited reason for SAD is low levels of sunlight, which coincide with low ultraviolet (UV) light in the winter. 

UV light has a short wavelength, placing it just outside the light spectrum visible to the human eye. It is produced naturally by the sun and is strongest during the spring and summer months. 

Heightened UV exposure that takes place during the summer is thought to improve mood. UV light boxes may supplement reduced winter UV light availability and thus help treat SAD.

Interestingly, most of the UV light boxes have been used to aid in the treatment of other health conditions, like psoriasis. For those who suffer from SAD, UV-free lightboxes can work just as well, and they’ll also be easier to get your hands on if you’re ordering one online. 

Vitamin D and serotonin

UV light boxes are thought to take effect through their influence on the vitamin D pathway, as UV exposure on the skin is required for the body to synthesize vitamin D. 

Vitamin D receptors are present in the brain, and some experts suggest this vitamin may thus have a modulatory effect on mood.  It has, in turn, been directly demonstrated that lower vitamin D serum levels can exacerbate depressive symptoms³ and may produce mental disorders such as depression.

If UV exposure facilitates vitamin D synthesis, then it may also facilitate improvements in mood. 

Still, others point to vitamin D’s role in the synthesis of serotonin as the factor underlying UV light therapy’s effect on SAD. Serotonin is a neurotransmitter, often colloquially referred to as the “happy molecule.” The serotonin hypothesis proposes that low serotonin transmission is highly influential in the development of depression. 

If UV light boosts vitamin D levels, which increases sequential serotonin synthesis, then it may help increase positive mood.

How to use UV lights for seasonal affective disorder

As with any other treatment, it is essential to first discuss your options with a healthcare professional. UV light or light boxes may be inappropriate for some individuals.

To maximize the UV light box efficiency, you should follow some general rules. It is important to note here that different lightbox models may have slightly different use instructions. 

You should adhere to the manufacturer’s recommendations. 

Timing of use

It is recommended that UV light boxes should be used within the first hour after you wake up in the morning. This treatment could be done while you eat breakfast, read a book, or are getting ready for your day. 

Timing has been shown to greatly influence the efficacy⁴ of SAD treatment.

Duration of use

Most researchers and manufacturers recommend light therapy be administered for around 20–40 minutes daily, often with periods closer to 40 minutes being more efficacious. 

However, this time may vary based on the size and brightness of the specific box you use. Boxes with larger surface areas are often brighter and require lower durations of use, while smaller ones may require more time to be effective. 

Distance from the lightbox

You should place yourself about 40–60 cm away from the lightbox to maximize efficacy and minimize any possible damage. 

If you’re doing something else during this treatment (e.g., eating, reading), be mindful of staying within the desired range.

Use it with your eyes open, but do not stare directly at it

Although most experts discourage looking directly at the light box due to possible eye damage caused by UV light, it is still recommended that your eyes remain open while using it. 

Some of the UV light can be absorbed through the retinas and may be quite useful in reducing the effects of SAD. 

Use as a complement to other treatments

UV light therapy is usually considered an adjunct to other depression treatments. 

Individuals should not cease these other treatments without professional consultation. In fact, light therapy can be particularly useful in combination with these treatments when one’s response to those treatments is less significant than expected, as is the case with many selective serotonin reuptake inhibitors (SSRIs).

Does UV light actually benefit SAD sufferers?

There’s been quite a bit of research on the use of light boxes for SAD treatment over the years. Results have been mixed.

One particular meta-analysis⁵ demonstrated that, in the vast majority of cases, UV light exposure provides positive enhancements to mood and eases depressive symptoms. This systematic review also suggested that UV exposure through receptors—such as the eyes and skin—decreased individuals’ scores on depression rating scales. 

Another 2016 study⁶ investigated the effect of UV light on sub-syndromal SAD. The study found that 20 minutes of UV light box exposure for five consecutive days significantly reduced SAD symptom ratings, demonstrating an effective treatment. 

Other studies⁷ have also shown that light therapy improves sleep-related pathology, which can improve SAD symptomatology. 

However, some researchers have suggested⁸ that many of the studies examining light therapy efficacy do not meet the criteria for rigorous experimental design. This may be due to difficulty in administering a placebo and difficulty in blinding participants.

What to consider when purchasing a lightbox

Although UV and UV-free lightboxes can be purchased without a prescription, it is important to first consult your doctor. 

Light boxes can be expensive, potentially damaging, and are not covered by health insurance. 

If a doctor’s approval is obtained, there are a few points you should consider before making your purchase. Some light boxes are inherently better than others. 

Look for a light box that produces 10,000 lux

A light box that produces 10,000 lux has demonstrated significant reductions in the depression rating⁹ of patients with SAD. This lux intensity is significantly brighter than standard indoor lights, as it will aim to mimic the stronger light of the sun. Boxes with lower lux outputs may need to be used for longer to reap the same benefits.

Consider what the light box is made for

Light boxes have a variety of uses, including the treatment of psoriasis. Such boxes may offer variations in brightness or size that may not be as useful for treating SAD. 

It is important to purchase a box specifically designed for SAD treatment, as this will provide you with the greatest efficacy. This can also include light boxes that are UV-free. 

Shape and size

It is important to consider the shape and size of the lightbox. Larger lamps often provide more lux and can be used for shorter durations; however, they may be more expensive and can take up extra room in your home. 

If you can afford to spend a little more time on treatment, a smaller light box may be a better fit. Smaller boxes will provide lower lux outputs, but if they are used for longer periods, they’ll offer the same results.

Possible risks of UV light box

As with any treatment, the UV light box use does have potential side effects. Some light boxes, including UV light used for other purposes, have caused damage, especially among people who have lens and cornea damage. Researchers have suggested that retinal damage¹⁰ may also occur. 

An overview¹¹ of SAD even suggests that those light boxes emitting UV wavelengths should be avoided due to this possible damage to the eyes. 

Patients with previous ocular pathologies such as cataracts or glaucoma are usually discouraged from using these light boxes. 

However, further studies¹² suggest that individuals using light therapy for SAD are unlikely to suffer ocular damage when the therapy is used over a short period. The same study also demonstrated no abnormalities in the individuals’ ocular function, even after three years of light therapy use. 

The use of UV light therapy is not recommended in conjunction with medications that cause photosensitivity. These medicines can increase your sensitivity to sunlight—and UV light in particular—which can, in turn, increase your risk of skin cancer from UV exposure. 

Some other common and more benign side effects include:

  • Eyestrain

  • Blurred vision during use

  • Headaches

  • Spots in vision if individuals stare directly at lightbox

In comparison to the side effects of antidepressants, which can include liver damage, seizures, and cardiovascular issues, these side effects may seem milder and more preferable to many. 

Although light boxes are generally considered relatively safe if used properly, individuals should note they are not FDA-approved or regulated. Users should fully consider all risks before undertaking light therapy. 

A relatively uncommon side effect of light therapies, including UV light therapy, is hypomania. It has been noted¹³ that individuals with SAD and comorbid bipolar disorder can experience an improvement in seasonal depressive symptoms but paired with periods of mania in their remission seasons. 

A review¹⁴ of light therapy in people with seasonal depression, however, suggests that hypomania or mania is a relatively uncommon side effect of light therapy.

The lowdown

Light boxes have demonstrated varied but largely positive effects in the treatment of the seasonal affective disorder. Both UV and UV-free light boxes may be an exciting and effective new option for some SAD sufferers. 

The side effects are also usually less severe than those of antidepressants. For some people, therefore, UV light therapy may be an effective treatment option for SAD.

  1. Seasonal affective disorder: An overview of assessment and treatment approaches (2015)

  2. Seasonal variation of mixed and pure episodes of bipolar disorder (2002)

  3. Vitamin D serum level in major depressive disorder and schizophrenia (2020)

  4. Circadian Time of Morning Light Administration and Therapeutic Response in Winter Depression (2001)

  5. Effect of ultraviolet light on mood, depressive disorders and well-being (2018)

  6. The effects of low-intensity narrow-band blue-light treatment compared to bright white-light treatment in sub-syndromal seasonal affective disorder (2016)

  7. Illuminating Rationale and Uses for Light Therapy (2009)

  8. The efficacy of light therapy in the treatment of mood disorders: A review and meta-analysis of the evidence (2005)

  9. Short exposure to light treatment improves depression scores in patients with seasonal affective disorder: A brief report (2010)

  10. Ocular and systemic melatonin and the influence of light exposure (2018)

  11. Seasonal affective disorder (2012)

  12. Ophthalmologic examination of patients with seasonal affective disorder, before and after bright light therapy (1995)

  13. Rapid mood swings after unmonitored light exposure (1998)

  14. Light treatment of mood disorders (2003)

Other sources:

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.

Joining community groups and exercise programs for my condition made me feel empowered – but I want to be part of finding a cure.
Peter, 64


Join our email list

Want all the latest clinical trial and HealthMatch news in your inbox? We thought you might! Sign up below.