To use a light box effectively, sit about 12 inches from a 10,000-lux device for 30 minutes each morning, with the light angled toward your eyes but not stared at directly. Most people notice improvements within a few days to two weeks of consistent daily use. Getting the details right, from timing to positioning, makes a real difference in whether the therapy works.
Choosing the Right Light Box
Not all light boxes are created for the same purpose. Devices designed for skin conditions primarily emit ultraviolet light and can damage your eyes. You want a box built specifically for mood-related light therapy. The key specs to look for are straightforward: 10,000 lux of brightness, effective UV filtration, and a size that fits your routine. Smaller, rectangular models travel well. Larger upright models cover a wider angle, giving you more freedom to shift position during a session. The best light box is the one you’ll actually use every day, so prioritize convenience.
Brightness matters because it determines how long you need to sit. A 10,000-lux box requires about 30 minutes per session. A dimmer box, say 5,000 lux, would need roughly an hour to deliver the same total dose. Research supporting light therapy’s effectiveness is largely based on broad-spectrum white light boxes rated at 10,000 lux, so that’s the standard to aim for. Devices producing at least 7,000 lux at 12 inches have also shown results in recent studies, but 10,000 lux remains the most well-supported option.
When to Use It
Morning is the optimal time. Most research points to sessions before 8 a.m., started soon after you wake up. Light therapy works by influencing your body’s internal clock through the eyes, and morning exposure aligns your circadian rhythm the way natural sunrise would. This helps suppress melatonin production at the right time and signals your brain to shift into daytime mode.
Consistency matters more than most people expect. Use your light box at roughly the same time every day, including weekends, holidays, and vacations. Studies that showed the strongest results required participants to keep a regular wake-up time and a fixed session schedule. The effectiveness of inconsistent timing hasn’t been established, so treat it like a daily habit rather than something you do when you remember.
If morning sessions alone aren’t working after two to four weeks, adding an evening session around 8 p.m. may help. Evening sessions typically run 30 to 60 minutes. A small number of people respond better to evening light than morning light, but start with mornings and adjust from there.
How to Position Yourself
Place the light box on a desk or table so it sits slightly above eye level, angled downward toward your face. Keep it about 12 inches away for a 10,000-lux device (check your specific model’s instructions, since recommended distance varies with brightness). Your eyes need to be open, but you should never stare directly into the light. The therapeutic effect works through indirect exposure: the light enters your eyes while you look slightly away, reading, eating breakfast, or checking your phone.
This makes light therapy easy to fold into your morning routine. Many people set the box beside their computer or next to their coffee and cereal. The 30 minutes pass quickly when you’re doing something else. Just make sure the light is actually reaching your eyes and not blocked by a hat, sunglasses, or a turned head.
What to Expect in the First Few Weeks
Some people feel a difference within the first few days. Energy picks up, sleep quality improves, and the heavy, foggy feeling of seasonal depression starts to lift. For others, it takes closer to two weeks of consistent use before changes become noticeable. If you’re not seeing improvement after four weeks, that’s a signal to reassess your setup: check the lux rating, your distance from the box, your timing, and whether you’ve been truly consistent.
Light therapy works best as a sustained daily practice throughout the darker months, not as a short-term fix you stop once you feel better. Stopping too early often brings symptoms back.
Side Effects and How to Manage Them
The most commonly reported side effects are headache, eye strain, irritability, and nausea. In practice, these tend to be mild and often fade after the first several sessions as your body adjusts. Research on healthy adults found that eye strain and blurred vision did occur during 30-minute sessions, but at similar rates whether participants were using a real light box or a placebo device. The visual discomfort may have more to do with the activity performed during the session (like sustained reading) than the light itself.
If side effects bother you, try sitting a few inches farther from the box, shortening your session by five or ten minutes, or taking a brief break midway through. You can gradually work back up to the full 30 minutes over a few days.
Who Should Be Cautious
Light therapy isn’t appropriate for everyone. People with bipolar disorder face a real risk: bright light can trigger manic or hypomanic episodes. Current mania, recent hypomania, mixed mood symptoms, and rapid cycling are all contraindications. If you have bipolar disorder and want to try light therapy, it requires careful medical supervision.
Retinal diseases and other eye conditions also warrant caution. Certain medications increase sensitivity to light, including some antibiotics, antimalarials, and St. John’s Wort. If you have reduced vision, recent changes in your eyesight, or a history of eye disease, an eye exam before starting is a smart step. People who’ve had LASIK surgery should wait at least four weeks post-procedure and confirm with their eye doctor that healing is complete before beginning sessions.