Common Side Effects From Light Box Therapy and Ways to Alleviate Them

Headaches, Mood Changes May Result from Phototherapy

Light can have profound effects on our ability to sleep. It may impact the ease in which we fall asleep and wake in the morning. It can also impact our mood.For example, in the dead of winter, it can become difficult to wake up and get the day started due to morning sleepiness. With chronic circadian disorders, such as in those who are night owls by nature, insomnia may also occur at night. If you have been advised to use a light box for phototherapy to treat your circadian rhythm disorder or seasonal affective disorder (SAD), you may wonder if there are any potential common side effects with light box therapy and ways to alleviate them. Light therapy glasses may be another treatment option as well. Fortunately, there are very few side effects with this type of phototherapy and if they do occur, they are quickly reversible once therapy is stopped.

Some of the potential side effects that may occur include:


Light box therapy may cause photophobia, literally a fear of light
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The light emanating from the light box itself may prove bothersome, inciting a case of photophobia (literally, "fear of light"). If you have this symptom, you may experience a light sensitivity that may even cause eye pain. Associated symptoms may include squinting. You may find that the light is irritating and something you simply feel compelled to avoid. This may lead to looking away from the light excessively and intolerance that shortens the treatment period.


Light box therapy may cause a headache as a side effect

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A headache may result from the use of a light box, especially if you are prone to migraine headaches. The bright light may intensify the discomfort. It may come on suddenly. Some may fade quickly with discontinuation whether others could persist for a prolonged period. 


Light box exposure at the wrong time may cause increased fatigue

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Curiously, the light box may actually incite a case of fatigue. This may occur if your circadian rhythm becomes shifted inappropriately. Using the light in the evening when you are a night owl, for example, would cause worsened morning fatigue. Your body may suddenly be compelled to sleep later into the morning and as a result, you will naturally feel fatigued at that time with difficulty waking. This would also be associated with difficulty falling asleep at the beginning of the night, or sleep-onset insomnia, as discussed later.


Irritability or mood problems may occur in some as a side effect to light box therapy

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In some people, the use of a light box may result in increased irritability. You may find yourself losing your patience with others, becoming annoyed, and unexpectedly snapping at them. This may have negative impacts on professional or personal relationships. There can be other mood changes as well.


Woman up at night in the fridge

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There are situations where a light box can actually provoke an episode of hypomania. Mania is a period of elevated mood and increased activity. It often occurs cyclically with bipolar disorder. In predisposed individuals, the light box may cause a milder form of a manic period called hypomania. This may be tolerable, but it could also lead to some adverse behavioral changes.


Light box may cause insomnia as a side effect and make it hard to fall asleep

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Finally, the light box itself may cause difficulties falling or staying asleep called insomnia. Again, this likely relates to a shift in the circadian rhythm and the body's desire to sleep. If the light box is used at the wrong time, such as in the evening in night owls, it may result in improper timing and a delay of sleep. This is one reason why it can be important to avoid screen light before bedtime.

Ways to Alleviate Side Effects

Light box therapy can be used effectively to minimize side effects
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Many of these negative side effects associated with light box use might be improved by taking a few simple steps. First, you might simply increase the distance you are sitting from the light box. Additionally, it might be necessary to take short breaks or even shorten the session times. Some devices may allow you to reduce the intensity of the light. By reducing the intensity or the amount of time that you are being exposed, the side effects might go away.

For those with sensitive skin, migraine headaches triggered by light sensitivity, or a tendency to mania such as in bipolar disorder, it may be best to simply avoid light box phototherapy all together. 

A Word From Verywell

If you have questions or concerns, you should speak with your healthcare provider about your treatment and possible alternatives. Traditional light boxes, and even newer light therapy glasses, can provide relief in those who need the treatment. It is possible to sleep normally and feel better, and phototherapy with a light box may help.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading
  • Kryger MH, et al. “Principles and Practice of Sleep Medicine.” Elsevier, 6th edition, 2017.

By Brandon Peters, MD
Brandon Peters, MD, is a board-certified neurologist and sleep medicine specialist.