What Are The Best Lights For Seasonal Affective Disorder?

Seasonal affective disorder (SAD) is a subtype of major depression, caused by a change in seasons. SAD differs from major depression in that it occurs during a particular season, usually winter, with full remission for the rest of the year. 

About 5%¹ of the US population experience seasonal affective disorder. The condition is most common among females, those aged between 18 to 30, and those with a family history of depression. 

An effective way to treat SAD is with light therapy, which can help to relieve symptoms by regulating your biological clock.

How do lights help seasonal affective disorder?

Limited exposure to sunlight is a key cause of seasonal affective disorder. Lack of light leads to lower levels of vitamin D, a reduction in serotonin, and excess melatonin production. 

Melatonin is a hormone produced in the pineal gland of the brain which regulates sleep by causing you to feel tired at nighttime. The production of melatonin is inhibited by light and stimulated by darkness. 

Cells in your eyes sense when it is getting darker in the evening and send a signal to the suprachiasmatic nucleus² (SCN) in your brain. The SCN then tells the pineal gland to produce melatonin, which is released into the bloodstream. This process occurs about two hours before you fall asleep. 

During the day, melatonin levels in your bloodstream should be very low as sunlight inhibits melatonin production. 

During the winter months, the days are darker and shorter so there is less sunlight. This may cause melatonin to be produced³ even during the day, resulting in excessive melatonin in the bloodstream which can cause sleepiness. This is a common symptom of seasonal affective disorder and disrupts your body’s biological clock, called your circadian rhythm. 

Exposure to sunlight helps your body produce both vitamin D and serotonin, whereas too little exposure to light and too much darkness can lead to deficiencies that are associated with depressed mood, low energy, and other symptoms of seasonal affective disorder. 

A first-line treatment option for SAD is light therapy, which has been used since the 1980s.⁴ Light boxes mimic the sunlight lost during the winter months in order to regulate your circadian rhythm⁵ and stop the production of melatonin during the day. Light boxes may also help restore serotonin levels. 

Side effects

Light therapy is considered to be a safe treatment option for seasonal affective disorder, but there are a few minor side effects that may occur. These tend to present at the beginning of light therapy and only last for the first few days. 

Side effects of light therapy may include: 

• Nausea

• Headache

• Dizziness

While light therapy used to treat SAD does not damage your eyes, it is important to get your eye health checked before starting light therapy. 

Some medications, like St. John’s wort, can increase your photosensitivity, meaning your body is more sensitive to light. If you are taking any medication, you should check with your doctor whether light therapy will result in any such complications. 

What kind of light is best for seasonal affective disorder? 

There are lots of light therapy products available. Use the following section as a guide to make sure you buy the right light box for your seasonal affective disorder treatment.

Intensity

Light boxes with an intensity of 2,500 to 10,000 lux¹ are suitable for SAD treatment, with 10,000 lux being the most recommended intensity. 10,000 lux is the light intensity of the sky just after dawn. Using a light that accurately mimics this time of day shortly after waking up will help to regulate your circadian rhythm and halt the production of melatonin. 

As light boxes generate much more intense light than the regular lights in your home, your home lights will not be effective for SAD treatment. 

If you use a light box with a lower light intensity, you will need to increase the length of your exposure and sit closer to experience the same benefits. 

Screen size

When purchasing a light box, you should choose one with a minimum screen size of 155 square inches, or 11 inches x 15 inches. The larger the better, because light intensity decreases the further you are away from the light source. 

If you turn your head slightly away while using your light box, you will decrease the amount of light you are exposed to which can result in you being under-treated.

To avoid this, use a light box with a large screen size covering as much area as possible. 

UV filter

It is essential to use a light box that filters out ultraviolet (UV) light. UV rays are harmful to your eyes and do not offer any benefits for SAD treatment.  Some light therapy products do not have a UV filter, which is used to treat certain skin conditions. 

Color temperature

The best light boxes for SAD treatment produce a cool white light, with a color temperature of less than 5000 kelvin (K). 

A number of light therapy products are advertised as “full-spectrum”¹ or with a color temperature above 5000 K, which are effective for treating SAD. However, they do not provide more benefit than those that are not “full-spectrum” or under 5000K. They are also often more expensive and may cause glare. 

Light boxes with a stand

When using your light box, it is best to place it above eye level, tilted down towards your eyes. You should place your light box about 14 inches⁶ away from your eyes, or closer if your light box is a lower intensity than 10,000 lux. 

Light boxes with an adjustable stand make it easier to position your light box. 

Where to buy a light box for seasonal affective disorder

Wherever you choose to buy your light box, make sure you check the specifications first. Use the above section as a guide for the minimum requirements. If a product does not meet these requirements, you are unlikely to see sufficient improvement in your symptoms. 

Ecommerce sites like Amazon offer many different kinds of light boxes. You can also purchase light therapy products at stores like Best Buy and Walmart. 

Prices vary widely, usually based on the screen size. Some products are around $40, while others can be as expensive as $200. A light box of adequate size — at least 155 square inches — is likely to cost about $120. 

What are the specifications to be looking for?

When purchasing a light therapy product to treat SAD, ensure that the light box filters UV light, produces a cool white light and has a screen size of at least 155 square inches. A light box with a light intensity of 10,000 lux is ideal and it should also have a stand for ease of positioning. 

An example of a good light box for treating seasonal affective disorder is the Carex Day-Light Classic Plus light box. It costs approximately $120 and meets all of the required specifications. 

It has a large screen size — slightly larger than 15 inches by 12 inches — and has an adjustable stand to position it at the ideal height and angle. It has a light intensity of 10,000 lux when placed 12 inches away from your eyes, and its cool white color temperature is 4000 kelvin. In addition, it blocks 99.3% of UV light. 

The lowdown

Light therapy is a proven treatment for seasonal affective disorder. It works by temporarily inhibiting melatonin production, decreasing common symptoms of seasonal affective disorder, and helping to restore serotonin levels which improve your mood.

Light boxes used for light therapy are available to purchase both online and in stores throughout the US. 

When selecting a light box, make sure that it meets the requirements for SAD treatment, as there are light therapy products that are used for other conditions and are not effective in treating SAD. 

Before starting light therapy, it is important to discuss with your doctor whether it may assist with your symptoms. You should always use your lightbox as directed by your healthcare provider.