Blue light therapy may help with depression, but it is still not clear exactly how effective it is.

Depression is a mood disorder associated with a loss of interest in activities, low mood, and similar symptoms for 2 or more weeks. Current treatment guidelines suggest medication, cognitive behavioral therapy (talk therapy), or both for most people.

Evidence is not as clear on the effectiveness of blue light therapy. It may work well for people with seasonal affective disorder (SAD). Additionally, some evidence suggests it can help with other forms as well.

This article reviews in more detail what blue light therapy is, how it may treat depression, what the research says, and more.

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Blue light therapy uses light to treat conditions that typically occur on or just under the skin.

Photoreceptors within the eyes are sensitive to low-wavelength blue light. These receptors provide information to help regulate a person’s biological clock and other areas of the brain. Based on that, a 2016 study explores how blue light therapy could help treat SAD and other forms of depression.

The exact mechanism by which blue light therapy treats depression is unclear. However, experts hypothesize that it:

  • alters the circadian rhythm
  • suppresses melatonin secretion
  • modulates serotonin levels in the brain

In other words, blue light may help regulate emotional responses in the brain. This can be especially helpful for areas of the brain that depression typically affects. These areas include the hippocampus, hypothalamus, and amygdala.

A person can often acquire a blue light device from online retailers. Devices vary considerably in the intensity and light wavelengths emitted. Despite this, some research indicates they can still help some people with SAD.

In a 2016 study, the experimental group had 20 minutes of blue light exposure each morning for 5 days. However, an individual’s treatment time and duration outside of clinical studies may vary.

A person may want to discuss their plans with a doctor or other healthcare professional before starting blue light therapy at home. A professional may be able to provide advice on what device to use, and when and how to use it.

Experts generally consider blue light therapy to be a safe procedure.

However, side effects may occur. According to the 2016 study, some reported side effects include:

The side effects in the blue light group occurred roughly as much as those in the bright light group.

Most evidence points to the use of blue light therapy for SAD, a form of depression. Less evidence supports its use for major depressive disorder, more commonly known as “depression.”

As a result, people with major depressive disorder may not benefit as much as those affected by SAD.

Another potential con is the lack of evidence supporting its use. For example, the use of blue light therapy for SAD or major depression remains unproven.

A person should also avoid using the therapy in the evening since it could mess up their sleep cycle.

The National Institute of Mental Health (NIMH) also does not list blue light or any light therapy as a potential treatment for depression. Instead, it recommends:

  • talk therapy
  • medication
  • a combination of talk therapy and medication
  • brain stimulation therapy using electric or magnetic pulses

The NIMH does note, however, that other forms of brain stimulation are still experimental.

Most recently, a 2022 meta-analysis reviewed the results of several studies looking at how blue light therapy helps with depression. It notes that the evidence is currently lacking to support its use for depression.

However, they did note that additional, longer, and larger studies may help to prove its effectiveness for use in depression.

Early studies were generally more positive. A 2016 study of blue light use for subsyndromal SAD finds that blue light is just as effective as bright light. Subsyndromal means that a person has symptoms that are not severe enough to meet the diagnostic criteria for a disorder.

Older studies also show some positive results. In a 2009 study, researchers study the effects of blue light on people with SAD for 3 weeks. They note that it worked better than red light therapy. In this study, blue light also worked as well as bright light therapy in previous studies.

People interested in blue light therapy may want to approach its use with caution. A person should not discontinue current treatments to try the therapy. They should also discuss their interest with a doctor before trying the therapy.

A person should follow all instructions from the manufacturer and their doctor when using light therapy devices at home.

Studies indicate that the therapy is most effective in the morning. Similarly, people should avoid nighttime use. Up to 20 minutes of exposure for 5 days may improve symptoms of sub-syndromal SAD.

The length of treatment may vary between people.

Per the previous 2016 study, blue light may only need about 5 days of morning exposure to be effective. However, this study only observed blue light’s effects on sub-syndromal SAD. This is a condition that has symptoms of SAD but was not severe enough for a clinical diagnosis. As such, more research is necessary on the effectiveness of blue light therapy for diagnosed SAD and depression.

A doctor may recommend additional sessions depending on the person’s response to treatment and need.

Blue light therapy may help some people with depression regulate certain symptoms. This therapy seems most effective in people with seasonal depressive disorder. However, other forms of depression may also benefit from it.

Research has been generally positive. However, current analyses suggest that blue light therapy is still an unproven therapy.

People should use caution if starting therapy. They should consult with a doctor before starting it or stopping other forms of treatment.