When we’re exposed to sunlight, the production of serotonin is triggered in our bodies. Serotonin is a hormone that plays a key role in regulating your mood and promoting feelings of happiness.

Not getting enough sunlight can lead to lowered serotonin levels. It’s thought that this dip in serotonin during the darker winter months may contribute to seasonal affective disorder (SAD). Light therapy can be incredibly effective in treating SAD, and may prove beneficial in the treatment of certain sleep disorders.

What is light therapy?

Light therapy — also known as phototherapy — works by recreating the effect of natural sunlight using artificial light.

Most light therapy devices provide 10,000 lux (a unit that measures light intensity). This level of light is similar to that of the afternoon sun. The goal is to mimic the sunnier days of the summer so that you can enjoy the serotonin-boosting effects of sunlight exposure, even in the fall and winter months when the sun sets early.

There are many light therapy boxes and lamps available on the market today. Light therapy devices usually have fluorescent lights on a metal reflective base, and a plastic screen is included on top to diffuse the light and filter out ultraviolet light (UV) rays. You can even find light therapy alarm clocks, which fill your bedroom with progressively brighter light for 30 minutes before you’re due to wake up to ease you into the morning smoothly.

What does light therapy do?

Light therapy helps your body produce more melatonin, serotonin, and vitamin D. Because of this, it’s very effective in treating various mental health conditions and some sleep disorders.

Seasonal affective disorder (SAD)

Light therapy triggers a chemical change in your brain, causing you to produce less melatonin (a sleep-promoting hormone) and more serotonin (a mood-boosting hormone). The positive effects of light therapy can be felt in as little as a few days, but some find it can take up to two weeks of treatment to notice mood improvements.

A 2017 study found that 61% of participants with SAD who underwent light therapy over four weeks experienced a remission of their symptoms. Since the designation of SAD as a mental health disorder in the 1980s, research has proven that bright light therapy can be a highly effective treatment.

Because of all of its mood-boosting benefits, light therapy can also be a welcome addition to treatment plans for depression that is not seasonally related.

Circadian rhythm disorders

Light therapy can be used for circadian rhythm sleep disorders, which are sleep conditions related to your body clock. For example, if you have trouble falling asleep but no trouble staying asleep, you may have sleep onset insomnia. This is linked to irregular circadian rhythms.

Regularly feeling tired in the late afternoon or early in the evening is a sign of advanced sleep phase disorder. Those with this condition usually go to bed between 6pm and 9pm. Because they go to bed so early, they often wake up between 2am and 5am. In these circumstances, light therapy in the early hours of the evening can help recalibrate your internal clock.

If you find yourself staying awake late into the evening (often past midnight) and waking up later in the morning as a result, you may have delayed sleep phase disorder. In this case, doing your light therapy treatment early in the morning immediately after waking up can help by advancing your internal clock so you feel tired earlier in the night. 

Recent research has shown that light therapy may also be effective in preventing jet lag. It’s not generally recommended to use light therapy for sleep disorders not linked to irregular circadian rhythms.

How do you use light therapy?

Typically, daily light therapy treatment sessions should last between 20 and 30 minutes. Once your light therapy device is switched on, you simply sit close enough for your eyes and skin to absorb the light. Generally, you should try to sit within one and a half to two feet away from the lamp or box. Each device is different — always adhere to the manufacturer’s recommendations.

To avoid damage to your eyes, don’t look directly into your light therapy device for the whole session. Try instead to allow your eyes to pick up the light indirectly.

Pros and cons of light therapy

Light therapy is an affordable and effective way to treat SAD and certain sleep disorders. It’s:

  • Safe: while there are potential side effects (particularly if the lamp is used incorrectly), light therapy is typically low-risk
  • Noninvasive: light therapy can be an alternative to (or addition to) medications, as it doesn’t have to be taken internally
  • Accessible: you can complete your treatment at home as and when you please, using a rented or purchased light therapy device
  • Convenient: you can still carry out activities like reading or eating a meal while you complete your light therapy, meaning you don’t have to interrupt your day for your treatment 

You shouldn’t use light therapy if:

  • You have a medical condition that makes your eyes sensitive to light
  • You take medications that increase sensitivity to light

While the risk of side effects is low, there are a few negative effects that can occur, including:

  • Headaches
  • Strained eyes
  • Irritability
  • Issues with sleep
  • Tiredness
  • Blurred vision

Most of these symptoms can be prevented by changing how you use your light therapy lamp. If you’re experiencing symptoms that don’t disappear when you adjust the way you’re using your lamp, consult with your doctor to determine whether to continue with treatment.

We’re still learning about light therapy, how our bodies react to it, and what it can do for our minds. What we do know from research is that it can be hugely helpful in the at-home treatment of mental health conditions and sleep disorders.

If you believe you are suffering from seasonal affective disorder (SAD) or you feel a light therapy device would be useful in treating your sleep disorder, consult with your doctor for guidance.