Light Therapy

Depression has a lot in common with jet lag. Both make people feel tired, unmotivated, and foggy headed. Like jet lag, depression is caused in part by disruptions to the biological clock that regulates our circadian rhythm. That clock is set by light and darkness, which is why an extra dose of morning light can lift depression.

Light therapy was developed at the National Institute of Mental Health to treat winter depression, and it is one of the few natural therapies that is as potent as a medication. It also works in the summertime (perhaps because we spend so much of our lives indoors).

Light therapy is not just for depression. It can also improve PTSD, ADHD, binge eating, sexual dysfunction, insomnia, and Parkinson’s disease. However, we have only a few studies supporting its use in each of those conditions. For depression, we have nearly 100 studies.

To make this treatment work, you need to get the right light box and use it at the right time.

Choosing a Light Box

Be careful here. Most light boxes do not work. The top selling products are small and attractive, but they aren’t big enough to bring relief.

Fortunately, a researchers have stepped in to guide the public: The Center for Environmental Therapeutics. Below are boxes that have their stamp of approval or passed in clinical trials.

The Winner: Northern Lights Desk Lamp II

A little pricier ($180-220), but you’ll save on bulbs with the 30,000-hour life span. While Carex uses fluorescent bulbs, this model uses LEDs which are longer lasting and less likely to break. Also available from cet.org.

BOXelite OS

A bit bulky, but the legs easily come off for travel, as well as for height and angle adjustment. Fluorescent bulbs ($170-200 on Amazon, also available from cet.org).

Carex Daylight Classic Plus

A low-cost option with adjustable height stand, $100-120 on Amazon. The downside is that the fluorescent bulbs need replacement every 2-3 years. That costs $35, and as of this writing they are not available (Dl930 Replacement Bulb).

Carex Daylight Sky

Similar to the Daylight Classic, but with a different style at the base, $100-120 on Amazon. The downside is that the fluorescent bulbs need replacement every 2-3 years. That costs $35, and as of this writing they are not available (Dl930 Replacement Bulb).

How to Use a Light Box

Sit directly under the box for 1-2 hours a day to get the full effect. The box should hover over your head at a 45 degree angle, just like the sun. Keep within the distance your box recommends (usually 12-17 inches) and don’t stare directly into the light. You can read, eat, or use a laptop while under it.

Light is good for mood, but only in the morning. After 2:30 pm, light therapy can worsen mood by flipping the biological clock.

To find out the optimal time to turn on the light, go to www.cet.org and search for the AutoMEQ test, or use this free version here. Answer the questions based on how you’ve felt in recent weeks. At the end, your score will tell you the best time to turn on the box (usually between 5:00 am and 8:15 am). That’s the sweet spot, but don’t worry if you can’t start then. Get as close as you can.

Trouble waking up? Try a dawn simulator. These boost morning energy by creating a virtual sunrise at your bedside:

Light therapy takes 2-4 weeks to work, but you may feel better as early as 2-4 days after starting it.

Adjustments for Bipolar Depression

Light therapy works in bipolar depression, but can rarely cause manic or agitated symptoms. To minimize that risk, use the light between 12:00pm and 2:30pm. Start with 15 minutes under the box and gradually increase the time by 15 minutes each week until you are sitting under it for one hour a day. If manic symptoms occur (e.g. agitation, insomnia, restlessness, racing thoughts, irritability), contact your treatment team and lower the time under the box.

Starting and Ending Treatment

For winter depression, start light therapy at least 2 weeks before you anticipate a seasonal dip in your mood. As the light increases in the spring, you can taper it down over 2-4 weeks by decreasing the time under the box (e.g. lowering by 15 minutes per week). The sudden increase in light in March can trigger mania and agitation in people with bipolar disorder, so they may need to stop the lightbox in February. To reduce this risk of springtime mood problems, wear blue-light filtering glasses in the evening, starting in late February.

Risks

The most common side effect is headache and eye strain. Insomnia is possible, but sleep usually improves with early morning light. To protect your eyes, make sure your box has a UV filter and do not stare into the light. Let your doctor know if you have any eye diseases.

More on Seasonal Affective Disorder

Seasonal Affective Disorder (SAD) tends to start between ages 15 and 30. About 5% of people in the U.S. have SAD and up to 20% have milder forms of the condition. Northern climates have higher rates, but the rates don’t start to drop until you get below Columbia, SC. Winter depression is rare in the tropics (at or below Florida).

Learn more in Reset Your Inner Clock by Michael Terman, PhD.

–Chris Aiken, MD, Updated 5/16/2024

Key points

Light Therapy treats depression, bipolar depression, and PTSD. Improves energy, sleep, and concentration.
Works as well as medication (on average).
Works for winter and non-winter depression.
You’ll need the right box and technique to make it work.

Can’t wake up to start light therapy? Try a dawn simulator. It works while you’re asleep.

Most people get the best results with light therapy between 5:00-8:15 am. In bipolar disorder, it is safer between 12-2:30 pm. Using the box after 2:30 pm can worsen mood and sleep.