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Bright Light Therapy for Treatment of Seasonal Affective Disorder (SAD)

By Dr. Eappen

During the height of the COVID-19 pandemic in the Winter of 2020, I noticed that many of the most reliable treatments for depression were not having the same effect. These patients were running up against a once in a lifetime major psychological stressor (i.e., a global pandemic), on top of being isolated at home during the darkest days of the year (in terms of sunlight exposure and the season). It’s no surprise that they were struggling.

On the weekends, I would spend my time searching through psychiatric journals, digging for treatments that I hadn’t emphasized in the past or that deserved more of my attention. What I discovered seemed almost too simple, but there was no denying that it was effective. The treatment: bright light therapy (BLT).

Bright Light Therapy and SAD

Now, you may be familiar with light therapy as a treatment for seasonal affective disorder (SAD). Seasonal affective disorder is a condition in which patients typically experience recurrent depression during the fall and winter months and spontaneous remission in the spring and summer. Common symptoms include increased appetite with carbohydrate cravings, increased sleep, decreased energy, and marked decrease in activity.

So why does sitting in front of a bright light therapy box improve symptoms in patients with SAD? Scientists have a few basic theories here:

  1. Patients with SAD, as compared with a control group, have longer periods of melatonin secretion during winter/fall than during spring/summer. Melatonin is the hormone responsible for regulating sleep and wake cycles. Having more melatonin or longer periods when melatonin is released can lead to tiredness or low energy in patients with SAD. Exposure to BLT shortens the period during which their brain secretes melatonin.
  2. Patients with SAD, as compared with a control group, experience a disruption to their sleep/wake cycle due to seasonal changes in the length of daylight hours during the day. Morning light therapy may treat SAD symptoms by correcting this disruption and resetting their circadian rhythms.
  3. The serotonin levels in patients with SAD may also be affected by BLT. Serotonin is a neurotransmitter that plays a role in sleep, mood and anxiety. Serotonin levels are lowest in healthy adults during the winter months, but brain production of serotonin rapidly increases with an increase in light.

These and other studies show that a course (i.e., eight weeks) of daily BLT can greatly improve depression symptoms in patients with SAD, which is great news. But, what is even more exciting and aligns with what I discovered with my own patients are the findings from one study that looked at immediate light therapy effects. Let’s turn to these findings next.

Seasonal Depression

Improvement of Depression Scores After 1 Hour of BLT

Unlike studies that traditionally assess the effectiveness of BLT over several weeks, this study investigated whether depression would improve in patients with SAD immediately after bright light therapy (BLT). A total of 79 patients received 1 hour of bright light and 1 hour of red light (placebo) in randomized order. Researchers measured depressed mood at baseline and after each hour of light treatment using two self-report depression scales.

Findings: For both the first and second light sessions, the improvement of depression scores was greater for bright light than for red light (placebo), but these differences were only significant for the second hour. In the second session, bright light outperformed the placebo in terms of improvement on both of the depression scales used.

What is most interesting about these findings is how quickly this therapy works compared with other treatments for depression. With medication, it can take weeks for patients to feel relief from their symptoms. With BLT, on the other hand, patients can experience a small, but significant boost to their mood immediately.

This is not to say that BLT should serve as a wholesale alternative to antidepressant medication, however. Instead, I often recommend it to patients as an augmenting treatment for SAD in addition to medication or as a “bridge” treatment at the beginning of therapy while we work to find the right medication dosage. 

Still, for patients experiencing mild symptoms or for those who prefer not to take medication (e.g., because they are pregnant), BLT is a good alternative.

Here are the benefits my SAD patients have found using BLT:

  • Patients who experience improvement to their depression symptoms are more likely to adhere to ongoing treatment. Because depressed people often have a hard time taking their medications correctly, if we can give them even slight relief, it can improve their adherence practices.
  • Immediate mood improvement can alleviate hopelessness in patients dealing with depression. One study found that patients who report positive initial beliefs about antidepressant medication are more likely to be satisfied with their results at two months.

In other blog articles, I discuss the additional benefits of BLT. It can effectively treat, not just SAD, but all types of depressive disorders (seasonal, bipolar, major depression) as well as circadian rhythm sleep disorders. And, it can be an effective treatment any time of year, not just in the fall or winter months.

While traditional depression studies have focused on the effectiveness of BLT over the long term, i.e., assuming a delayed response to intervention, assessment of rapid effectiveness is important both for understanding the science of depression and for usage in a clinical setting. 

A modest but significant improvement in mood using bright light after just one hour offers a lot of patients hope. If you experience a dip in your mood, especially during the long, dark fall and winter months, bright light therapy is worth trying.

If you are experiencing depressive episodes, or have been diagnosed with seasonal affective disorder, major depression, bipolar disorder, or circadian rhythm sleep disorder (or you’re experiencing any other mental health challenges), please contact us. We are here for you.

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.