Beyond seasonal depression: how can bright light therapy be used in the management of mood disorders?

Michelle is a 45 yo woman with a history of recurrent major depression. She took several antidepressants in her 20s that were either intolerable (escitalopram) or ineffective (sertraline, venlafaxine). She has been taking fluoxetine 20mg for many years, which she says “puts a floor” on her depression. Higher doses of fluoxetine make her feel too activated.

She continues to have significant depressive symptoms every 2-3 years without a clear precipitant. She tried adding bupropion xl 150mg to the fluoxetine 20mg for depression augmentation but felt jittery on the combination. She has been in psychotherapy intermittently for many years with some benefit.

Michelle has been doing well for the last 2 years. Today, she reaches out to say that her early signs of depression are back – low energy, difficulty getting out of bed, and an increased desire to be alone. Michelle is working hard to exercise most days because she knows that this can help depression. She is also seeing her therapist weekly and taking the fluoxetine 20mg daily. She asks you if there is anything else that can be done to prevent things from getting worse. She doesn’t want to try anything that might cause her to gain weight.

What would you recommend adding to the weekly psychotherapy and fluoxetine for Michelle?

  1. Lithium
  2. Mirtazapine
  3. Aripiprazole
  4. Bright Light Therapy

The list of weight-neutral treatments or augmentation agents for major depression is short: psychotherapy, transcranial magnetic stimulation (TMS), electroconvulsive therapy (ECT), bright light therapy, and methylated folic acid (Deplin). Bupropion and T3 (Cytomel) are augmentation options for depression that may cause mild weight loss. Other commonly used augmentation agents for depression tend to cause weight gain, including mirtazapine, lithium and aripiprazole. If you are thinking – what are all these things?! – that’s ok. We are focusing on bright light therapy today and will cover the others in the future.

We’ve just passed the autumn equinox in the United States, which means that we are losing daylight fast. Some people have episodes of major depression that start in the fall and resolve in the spring. Bright light therapy has been studied and shown to be effective for this type of major depression–seasonal depression–since the 1980s. More recently, bright light therapy has been shown to be effective in non-seasonal depression as well, including both unipolar and bipolar depression.   

I’m going to 1) summarize an important 2016 study that established the effectiveness of bright light therapy for non-seasonal major depression and 2) tell you what you need to know to advise your patients about choosing and using a light box.

Lam and colleagues randomized 122 adults with non-seasonal MDD of at least moderate severity to one of 4 treatments. All patients took a pill (fluoxetine 20mg daily or a placebo pill) and sat in front of a device for 30 min daily (bright light therapy or a sham control (i.e. an inactive negative ion generator that made noise and was found to be credible with participants)). The experimental groups were placebo, fluoxetine, bright light therapy, and combination (fluoxetine + bright light therapy). The figure below shows the mean change in MADRS score (a depression scale commonly used in research studies) over 8 weeks. The light gray line represents the effect of bright light therapy on depressive symptoms. As compared with placebo (dark gray line), bright light therapy is more effective for depression after both 4 and 8 weeks. The combination of fluoxetine 20mg daily and bright light therapy (orange line) produced even more improvement in depressive symptoms. Response (defined as a 50% reduction in the MADRS score) was achieved by 50% of the bright light therapy group, 76% of the combination group, and 33% of the placebo group. The Number Needed to Treat for remission of depression for the combination (fluoxetine + bright light therapy) vs placebo was 3.5 (Lam, 2016).

Change in the Scores on the Montgomery-Asberg Depression Rating Scale (MADRS) at Each Treatment Week. Error bars indicate standard error. a, b, and c indicate p < 0.05 vs placebo (i.e. statistical significance)(Lam, 2016).

Not all studies of bright light therapy have been this impressive, but a 2016 review of bright light therapy as augmentation to antidepressants for nonseasonal depression (vs antidepressants alone) found an effect size of 0.5 for unipolar depression (Penders 2016).  

Michelle is impressed by the data for bright light therapy. She is open to a trial of bright light therapy added to the fluoxetine 20mg that she is already taking. How should she proceed?

The behavioral investment in bright light therapy is higher than for a pill. The shift towards working from home makes this treatment modality more accessible for some people now than in the past. Decades of studies have worked out established protocols for bright light therapy for depression. For either seasonal or non-seasonal major depression, start with 30 minutes of daily exposure to white fluorescent light at 10,000 Lux as soon as possible after awakening, preferably by 7am. Lux is a measure of illuminance – in this case, the intensity of light that reaches the eyes. If there is no improvement in depressive symptoms after several weeks, increase the exposure time to 45 or 60 min. If there is no response after 4 weeks, stop the treatment for lack of efficacy.  

Early morning is the most effective time for bright light therapy for unipolar depression. However, bright light therapy anytime before 2pm can have some benefit. People with bipolar depression may also benefit from bright light therapy, but midday treatments are preferred over early morning treatments because they are less likely to precipitate mania.

If depressive symptoms for non-seasonal depression improve with bright light therapy, continue the current dose of light therapy for at least 4 weeks after the resolution of symptoms. In the US, people with seasonal depression should continue bright light therapy until April when the light is back again, although it may be possible to reduce the dose (either by reducing the daily exposure time (20 min) or the frequency (every other day) without losing the benefit). Stopping light therapy mid-winter in people with seasonal depression most commonly leads to depressive relapse within 3 weeks. 

Both the efficacy and side effects of bright light therapy are dose dependent. Bright light therapy is generally well tolerated; if overactivation, hypomanic symptoms, nausea, or headaches develop, reduce the exposure time to improve tolerability.  

Michelle tells you that she’ll drink her coffee and read the morning paper while doing 30-minutes of bright light therapy in her kitchen. How can she get a light box set up?

Bright light therapy set-up for 10,000 Lux illumination
Apparatus Details: downward-tilted, smoothly diffusing, ultra-violet absorbing,
32 x 41-cm polycarbonate screen, soft-white fluorescent lamps
Photo credit from the Center for Environmental Therapeutics (Terman, CNS Spectr, 2005)

Get the right light box
Be careful. Light boxes are not federally regulated. Claims for effectiveness in depression are generally marketing slogans, and anything small enough to fit easily in a bag is likely to be ineffective. A sunny room does not approach the intensity of light needed for bright light therapy.

Here are 2 specific products to look for: 

  • Northern Light Technologies Boxelite OS Desklamp – $205
    This light box has been evaluated and is currently recommended by the non-profit Center for Environmental Therapeutics (CET), that also has detailed information on light and dark therapy for both patients and providers on their website ( Their link for this light box also includes a sample letter that patients can use to attempt reimbursement from their insurance through Durable Medical Equipment.
  • Carex Daylight Classic Plus – $140
    This light box is cheaper and meets all of the below criteria. It has been previously used in clinical trials of bright light therapy.

      General criteria that a bright light therapy box should meet:

      • Intensity & Size – 10,000 Lux illumination of both eyes at a comfortable distance (at least 12 inches) requires a large screen of at least 200 square inches. Avoid small, portable light boxes. They may advertise 10,000 Lux, but this illuminance is only achieved in a narrow field or at an uncomfortably close distance. 
      • Light – White light. Blue or full spectrum lamps are not more efficacious.
      • UV Filter – For safety, fluorescent lamps should include a polycarbonate filter that prevents ultraviolet rays from reaching the eyes and skin.

      Read the instructions with the light box and follow them. 
      Pay particular attention to the distance one sits from the screen, and the height and angle of the light box.  Lux is inversely proportional to the square of the distance from the light source, so small changes in how far one sits can render an effective treatment ineffective. Generally people sit at a table or desk and look down at a computer or book or their breakfast. It is fine to wear glasses, as long as they are not tinted or shaded.

      Key Points

      1. Bright light therapy is an effective treatment for both seasonal and non-seasonal depression.
      2. For major depression, start with 30 minutes of daily exposure to white fluorescent light at 10,000 Lux as soon as possible after awakening, preferably by 7am.
      3. Be careful in choosing a light box because they are not federally regulated. The details of the light box set-up are also important, in particular the distance one sits from the device.


      Eastman, Charmane I., et al. “Bright light treatment of winter depression: a placebo-controlled trial.” Archives of general psychiatry 55.10 (1998): 883-889.

      Lam, Raymond W., et al. “Efficacy of bright light treatment, fluoxetine, and the combination in patients with nonseasonal major depressive disorder: a randomized clinical trial.” JAMA psychiatry 73.1 (2016): 56-63.

      Penders, Thomas M., et al. “Bright light therapy as augmentation of pharmacotherapy for treatment of depression: a systematic review and meta-analysis.” The primary care companion for CNS disorders 18.5 (2016): 26717.

      Sit, Dorothy K., et al. “Adjunctive bright light therapy for bipolar depression: a randomized double-blind placebo-controlled trial.” American Journal of Psychiatry 175.2 (2018): 131-139.

      Terman, Michael, and Jiuan Su Terman. “Light therapy for seasonal and nonseasonal depression: efficacy, protocol, safety, and side effects.” CNS spectrums 10.8 (2005): 647-663.

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