Mood disorders

Does Light Therapy Work for Seasonal Depression?: What to know, plus a simple how-to guide

Dr. Kelemen, owner and psychologist at Bear Path Psychology and Wellness LLC in Nashua, NH. Dr. Kelemen provides therapy and assessment throughout NH and MA.

By Dr. Anthony Kelemen, PsyD

Oct, 2026

Does light therapy work for seasonal depression? What to know, plus a simple how-to guide. Join Dr. Kelemen in discussion around bright light therapy for seasonal depression.

It's that time of year again. If you've been in New England as long as I have, you know that Fall can be one of the most beautiful times of the year. However, up here in Nashua, New Hampshire and the rest of the northeast where we experience cold, dark winters, many experience a surge of depression that emerges like clockwork.

What is "seasonal affective disorder"?

Seasonal affective disorder (SAD), commonly referred to as "seasonal depression", is a term we use to describe major depressive episodes that recur with a seasonal pattern. The depressive symptoms usually emerge during early Fall or Winter and, for most people, resolve by Spring. It is estimated that about 5-6% of people experience SAD, and even more have symptoms at a milder level. Symptoms are significantly more common during the Fall and Winter months, although some experience similar mood changes in the Summer months as well.

Common Signs and Symptoms of Depression:

- Depressed mood

- Loss of interest

- Difficulty concentrating

- Appetite changes (overeating in particular)

- Sleeping more than usual

- Less energy than usual

- Trouble concentrating

- Feelings of worthlessness

- Thoughts of death or suicidal ideations

Why does seasonal depression develop?

For many years, researchers have studied a number of complex (and quite significant) connections between light, mood, and circadian rhythm. Researchers have even found associations between geographic location and SAD. One systematic review and meta-analysis found that the prevalence of SAD was significantly associated with latitude, or, how far north you live (Kim et al., 2025).

As light exposure changes with the seasons, our mood and sleep can change along with it. In addition to less light exposure in the Fall/Winter, our routines can change significantly as we put our flip-flops away and get the winter jackets out. Many people spend significantly less time outside exercising and doing other meaningful activities due to weather and daylight changes. Some individuals are also more prone to stress and depression during the colder months as the holiday season can be challenging in lots of different ways. Simply put, lack of light can have a negative impact on our mood and sleep, and that can be compounded with a number of other changes and seasonal stressors that come together which, for some, can create the perfect recipe for depression.

In terms of how it's treated, many do just fine with traditional approaches (e.g., psychotherapy, medication). However, "bright light therapy" has been used for years and remains very popular particularly among those with seasonal patterns of depression. In fact, many people swear by it and use it every year to help them get through the season.

What is bright light therapy?

Bright light therapy is exactly what it sounds like. It involves spending some time in front of a bright, artificial light in the morning and/or evening time. For decades, bright light therapy has been the subject of a number of research studies and clinical trials as a medication-free treatment for SAD. A 2026 systematic review and meta analysis examining 17 randomized controlled trials and crossover studies found that light therapy resulted in a reductions of symptoms when utilized for two weeks (Wu et al., 2026). There have also been studies on light therapy as a treatment for non-seasonal depression. A 2024 meta-analysis on 15 studies examining the effects of bright light therapy on non-seasonal depression found that those receiving bright light therapy experienced significant improvements compared to those who did not (Tong et al., 2024).

To answer the question "does light therapy work?", research has shown that it is a relatively effective, safe, and cost-effective treatment that can be done pretty much anywhere, but it's not as simple as just sitting in front of any light at any time. See below for a simple how-to guide, and learn about some of the possible risks and side effects.

A simple how-to guide for light therapy

1) Choosing your light box

For optimal effectiveness, you'll want to choose a light box that is strong enough to mimic the natural light you would be getting if you were outside in the sun during sunrise.

Look for a light box with with a minimum of 10,000 lux.

There are many brands to choose from (Verilux, Carex, Alaska Northern Lights, etc.), and it is ultimately just a matter of personal preference and budget.

2) Using your light box

It is generally recommended to sit in front of your light box for about 30min per day, as soon as you can after waking up, preferably around the same time each day.

Put your light box on a surface about 1-2 feet away from you. You do not need to stare directly at the light, or have it directly in front of you; the goal is to have it at a comfortable distance and directed toward your face. Many people like to have it on while eating their breakfast, walking on their treadmill, or starting their work day.

3) Consistency is essential

As with most kinds of treatment, consistency is very important; doing it a few times or doing it sporadically may not give you the results you're looking for.

According to Wu et al. (2026), light therapy is effective after "a minimum of two weeks." This meta analysis also noted that treatment effects were not significantly maintained, indicating that the benefits of light therapy unfortunately might not last very long once you stop using your light box.

For optimal benefits, aim to use your light box daily for at least two weeks, and continue using it for as long as you are comfortable and experiencing positive benefits.

Medication-free does not mean "no side effects"

As with any type of treatment, there are risks and benefits. While serious side effects of bright light therapy are uncommon, it is important to understand the potential risks.

- Eye strain

- Headaches

- Irritability

- Feeling overstimulated

- Increased risk of mania or hypomania in those with a history of (or proneness to) bipolar disorder

As always, it is important to consult with your healthcare providers before considering adding any new treatment to your routine.

Bright light therapy can be an effective way to help reduce symptoms of seasonal depression. It is not a "cure-all", and comes with its own risks, but its benefits are well-documented in research and people have been using it for years to help get through the season.

References

Kim, K., Kim, J., Jung, S., Kim, H.-W., Kim, H.-S., Son, E., Ko, D. S., Yoon, S., Kim, B. S., Kim, W. K., Lim, C., Kim, K., Lee, D., & Kim, Y. H. (2025). Global prevalence of seasonal affective disorder by latitude: A systematic review and meta-analysis. Journal of Affective Disorders, 390, Article 119807. https://doi.org/10.1016/j.jad.2025.119807

Tong, H., Dong, N., Lam, C. L. M., & Lee, T. M. C. (2024). The effect of bright light therapy on major depressive disorder: A systematic review and meta-analysis of randomised controlled trials. Asian journal of psychiatry, 99, 104149. https://doi.org/10.1016/j.ajp.2024.104149

Wu, C. J., Phiri, D., Jen, H. J., Setyowati, A., & Chung, M. H. (2026). Light therapy in seasonal affective disorder: A systematic review and meta-analysis of randomized controlled and crossover trials. Journal of Affective Disorders Reports, 24, Article 101021. https://doi.org/10.1016/j.jadr.2025.101021

This information serves as a reference and is for educational purposes only. This information is not intended to replace the clinical advice given to you by your own providers. Please consult with your medical and/or mental health team before considering adding any new treatment to your routine.