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Could Bright Light Therapy Be the Key to Treating Major Depressive Disorder (MDD)?

By Dr. Eappen

Bright light therapy (BLT) has been accepted as treatment for major depressive disorder (MDD) with a seasonal pattern for years. Better known as seasonal affective disorder (SAD), studies have found that patients who sit or work daily for about 30 minutes in front of a light therapy box, experience relief of symptoms such as sadness, anxiety, lack of energy, and increased desire to sleep.

More recently, however, psychiatrists and patients are starting to recognize the benefits of BLT for treating MDD (major depressive disorder). Used both as a monotherapy and as a supplement to other treatments like antidepressants (e.g., fluoxetine), BLT has been found to be effective. In fact, I often recommend BLT for my patients with MDD.

In this article, I explore the research into using BLT to treat nonseasonal depressive disorders.  

Bright Light Therapy: An Underused Treatment

Despite having a relatively low-risk for side effects and being easy for patients to control, BLT remains an underused treatment for nonseasonal depressive disorders. Why? There are a few reasons for this. 

One challenge for researchers is that it is difficult to conduct a placebo-controlled study with BLT. Placebo-controlled trials are the gold standard in medical research. Clinicians need to know whether symptom relief is the result of medical intervention or simply “psychological” effects.

Unlike with medication, where researchers can give study participants identical capsules to take and there will be no way for them to know whether they’re receiving the active ingredient or a placebo pill, participants easily know whether they are receiving light therapy. This makes some psychiatrists critical of research around BLT. Fortunately, technology makes placebo-controlled studies of BLT possible.

In the study I discuss below, patients were randomly assigned to receive either white light therapy from a light box or sham-placebo light from an inactive negative ion generator. Patients were given the same instructions whether using the light box or the ion generator.

Another reason BLT is an underutilized treatment for patients with depression is cost. While insurance companies cover medication and some other treatments for depression, they may not cover light-delivery devices. For some patients, cost can be a barrier here and doctors may be less likely to recommend this treatment for this reason.

Setting aside these obstacles, research into BLT shows that patients and doctors should give this therapy another look. 

The Research

One study in particular compared BLT monotherapy to fluoxetine (i.e., Prozac) monotherapy and combination (BLT + fluoxetine) therapy in patients with nonseasonal MDD. The study found that BLT was more effective than placebo and was well-tolerated in adults with MDD.

From the study: “This trial represents, to our knowledge, the first adequate-duration, placebo-controlled comparison of light monotherapy and combination light and antidepressant treatment. Previous studies of light monotherapy have been very short in duration or not sham controlled.”


Both light monotherapy and the combination treatment delivered significant benefits for participants with nonseasonal MDD. However, the most efficacious and consistent benefits were experienced by the group receiving the combination therapy. In both the interviewer ratings and patient self-ratings, the benefits of the combination therapy were apparent. 

Researchers noted one interesting difference between BLT for treatment of SAD and BLT for treatment of Major Depressive Disorder. In SAD studies, patients experienced benefits using light therapy within 1 to 2 weeks. Whereas in this study, patients saw steady improvement throughout the 8 weeks. This is a pattern of response similar to that of antidepressants.

Why Bright Light Therapy Helps

More research needs to be done to determine why light therapy reduces symptoms of depression. The main hypotheses in SAD patients involve reducing the amount of melatonin (a hormone responsible for sleep), resynchronizing circadian rhythms, and restoring neurotransmitter dysfunction.

Here’s what we know: Almost all of the functions of the body, including the sleep-wake cycle, follow specific rhythmic patterns throughout the day. These are driven by the “master clock” — i.e., the suprachiasmatic nucleus (SCN). Generally, people fall into one of three groups: “Early birds” go to sleep early and wake up early; “night owls” go to sleep late and wake up late; and there is a large third group of people who do not fall into either category.

Individuals with depressive disorders tend to be “night owls,” and as such, they are more prone to sleep disturbances. Because they may have trouble falling asleep at night and are awoken before they are ready when the sun comes up, it can be harder for night owls to feel well rested. So one hypothesis is that BLT moves melatonin onset up allowing them to go to sleep earlier.

Although circadian rhythm disruption can be a major factor in nonseasonal MDD, further studies will need to be done to determine the brain science driving the above results.

Potential Side Effects

Although the risk of side effects is low with BLT, some adverse effects have been reported. These include headache, eyestrain, nausea, and agitation. Reducing the dose tends to help with these side effects.

For patients with bipolar disorder, BLT can trigger manic episodes, and some patients have experienced an increase in suicidal thoughts early in the course of treatment. This is why it’s important to look at BLT as you would any other treatment. Figuring out what works for each individual patient is a matter of finding the proper dose, i.e., length of time, time of day, etc.

Finally, patients should avoid looking directly into the light. Staring into any bright light for too long can do damage to the retina. Ambient light is sufficient to receive the benefits of BLT.

Light therapy for depression


Given the risk vs. reward factor with bright light therapy, clinicians and their patients should be more aware of BLT.  Whether it is used as a part of a “combination therapy” alongside psychiatric medicines and psychotherapy, or as “monotherapy” where it is used alone, BLT has the potential to help many who suffer from any type of depression, whether it is bipolar depression, major depressive disorder, or seasonal affective disorder.

About the Author

Seth Eappen, MD, is a board-certified adult, child and adolescent psychiatrist. Dr. Eappen completed medical school at the University of Illinois at Chicago and a residency at the University of Michigan, Ann Arbor. He completed his child psychiatry fellowship at MUSC in Charleston, SC, where he served as chief fellow. He is the founder of the Eappen Clinic, a private outpatient mental health practice with locations in Chicago and Oak Brook, IL.