This article discusses how light therapy works and why light therapy lamps are so beneficial to people with SAD symptoms—like depression, hopelessness, and fatigue.
What Is Light Therapy?
Bright light stimulates the cells in the retina that connect to the hypothalamus (part of the brain that helps control the body’s daily rhythms).
Lack of adequate bright light, such as during the diminished daylight from fall to spring, can cause problems for people with certain conditions such as seasonal affective disorder (SAD).
One way to mitigate the effects of this reduction in sunlight is to engage in a treatment called light therapy.
Light therapy uses a device called a light box, which emits bright white light that mimics sunlight, to activate the hypothalamus.
Doing this at a certain time every day can help to restore a normal circadian rhythm (the body’s 24-hour sleep-wake cycle) and improve the symptoms associated with SAD.
These boxes typically provide 10,000 lux (a measure of light intensity). For comparison, indoor light is about 100 lux, and a bright sunny day outside is about 50,000 lux, sometimes more.
While primarily used to treat SAD, light therapy may also be helpful for:
Chronic depressionAntepartum depression (depression in pregnancy)Premenstrual depressionBipolar depressionDisturbances of the sleep-wake cycle
Light therapy should be used with caution or may be contraindicated for people with certain health conditions, including:
Macular degeneration and some other eye conditionsConnective tissue damageExisting skin cancersDiabetesLupus
How Are Light Therapy Lamps Used to Treat Seasonal Affective Disorder?
SAD is a type of recurring major depression with a seasonal pattern. Some symptoms of SAD may include:
DepressionIrritabilitySocial withdrawal/difficulty getting along with othersDifficulty concentratingFatigue/sleeping more than usualWeight gainIncreased hunger/carbohydrate cravingsA heavy feeling in the arms and legs
Daily light therapy sessions are used to help alleviate these symptoms. The specifics of these sessions include:
Sit approximately 12 to 24 inches from the box. Do not look directly at the light. Angle the box to about 30 degrees from the line of gaze. Sessions are usually done first thing in the morning. Treatments are typically used daily from fall to spring. Standard treatment is 10,000 lux for 30 minutes. Alternative treatment is 2,500 lux for one to two hours.
Improvement in symptoms is usually seen fairly quickly, often within days, but treatments must be continued to sustain these effects.
How to Choose a Light Therapy Lamp
When choosing your light therapy lamp, keep these things in mind:
Eyestrain Increased risk of age-related macular degeneration Headaches Irritability Difficulty sleeping
Less commonly, hypomania and suicidal ideation may occur, especially during the first few days of treatment.
Adjustable settings: Adjustable dimming and brightness settings allow for variety and versatility. Shape: Choose a lamp that fits in with your environment and suits your needs, be that portability, sturdiness, adjustable height, or other factors. Light intensity: The typical light therapy lamp is 10,000 lux brightness, but other options are available such as multiple brightness settings or modes that allow for gradual adjustments to daytime or nighttime. There are also different types of bulbs to choose from. Timer: A built-in timer eliminates the need for manual timing of each session.
A Word From Verywell
Light therapy is a recommended first-line treatment for SAD, with a documented history of helping improve symptoms.
If you suspect you may have SAD, or think you may benefit from light therapy, speak with a healthcare provider to discuss your options and see if light therapy is right for you.
Always read the manual that comes with your device to ensure you are following the instructions specific to that equipment.
One study found an immediate improvement in mood after the first session of light with exposures as short as 20 minutes. While encouraging, this study had limitations, such as a small sample size of 15 participants.
Stopping therapy sessions can make the symptoms reappear.
With lights that aren’t as strong, treatment sessions may be longer. For instance, a daily session may be one to two hours for a 2,500 lux lamp.
