A standard light therapy session lasts 30 minutes per day at 10,000 lux, typically done first thing in the morning. That’s the dose supported by the most research for seasonal depression and circadian rhythm issues. But the “right” duration depends on the intensity of your lamp, when you use it, and what you’re treating.
The 30-Minute Standard at 10,000 Lux
The most widely recommended protocol is 30 minutes of exposure to 10,000 lux light, done daily before 8 a.m. Yale’s Winter Depression Research Program notes that this schedule produces substantial improvement in seasonal affective disorder (SAD) for most people. Seven days a week is ideal, not just weekdays.
That 10,000 lux figure only counts at your actual sitting distance from the lamp. This is where many people unknowingly underdose. Some lamps produce 10,000 lux only at 6 inches from the screen, which is too close for a 30-minute session. Better-designed devices reach that intensity at 12 to 24 inches, a comfortable distance for reading or eating breakfast. If your lamp’s spec sheet doesn’t state the distance at which it delivers 10,000 lux, the number on the box is essentially meaningless.
Lower-Intensity Lamps Need Longer Sessions
If your lamp puts out less than 10,000 lux at your sitting distance, you need more time. The relationship between intensity and duration is roughly inverse: a 5,000-lux lamp would call for about 60 minutes, and a 2,500-lux lamp around two hours. Research confirms this tradeoff exists, but the longer sessions become impractical for most people, which is why 10,000-lux devices became the standard. If you’re unsure of your lamp’s output, sitting closer (within the range specified by the manufacturer) is one way to increase effective intensity without buying a new device.
Why Morning Matters
Light therapy works partly by resetting your internal clock. In people with winter depression, circadian rhythms tend to run late, with the brain producing melatonin on a delayed schedule. Morning bright light shifts that rhythm earlier, correcting the mismatch. A crossover study comparing morning and evening sessions found that morning light shifted melatonin onset significantly earlier in patients with SAD, while evening light pushed it later. Evening sessions can actually work against you if your goal is treating seasonal depression or a delayed sleep pattern.
For people with bipolar disorder, recent guidelines from the International Society for Bipolar Disorders recommend morning or midday sessions. Midday is a reasonable alternative if early mornings trigger excessively early wake times or feel unsustainable.
Starting Gradually
You don’t have to jump straight to 30 minutes. Starting at 15 minutes per day and adding 15 minutes each week is a common approach, especially for people concerned about side effects or mood instability. By the fourth week, you’d reach a full dose of 30 to 60 minutes daily. This gradual buildup is specifically recommended for people with bipolar disorder, but it’s a reasonable strategy for anyone new to light therapy.
How Long Until You Notice Results
Most people begin to feel a difference within one to two weeks of daily use. Full response, meaning significant or complete improvement in symptoms, typically takes four to six weeks. This timeline applies to both seasonal and nonseasonal depression protocols. If you’ve been consistent for four weeks with no improvement at all, it’s worth reassessing your setup: check the lamp’s actual lux output at your distance, confirm you’re using it in the morning, and make sure your eyes are open and facing the general direction of the light (without staring directly at it).
Light Therapy for Sleep and Shift Work
Shift workers use light therapy differently. For improving total sleep time, a meta-analysis found that medium illuminance (900 to 6,000 lux) for sessions of one hour or longer during the night shift was most effective. Higher illuminance and larger total light doses (intensity multiplied by time) were better for improving sleep efficiency. The protocols here are less standardized than for depression, but sessions tend to run longer and the timing shifts to align with the work schedule rather than defaulting to morning.
Side Effects and Safe Limits
The most commonly reported side effects are headache, eye strain, and mild irritability. These tend to show up during the first session and fade with repeated use. A placebo-controlled study in healthy adults found small but measurable increases in eye strain and blurred vision after a single 30-minute session at 10,000 lux, though the effects were mild. Nausea is occasionally reported but less common.
There is no firmly established upper limit for daily exposure, but clinical protocols rarely exceed 60 minutes at 10,000 lux. If you experience persistent headaches, agitation, or trouble sleeping, reducing session length by 15 minutes or shifting to a slightly dimmer setting can help. People with certain eye conditions or those taking medications that increase light sensitivity should discuss light therapy with their provider before starting.
Setting Up Your Lamp
Position the lamp within 6 to 24 inches of your face, slightly off to one side rather than directly in front. The light needs to reach your eyes, so keep your eyes open, but don’t stare at the lamp itself. Most people place it on a desk or table while they eat, read, or work on a computer. Angling it slightly above eye level mimics the natural position of sunlight and reduces glare. The key is building it into something you already do every morning so it becomes automatic rather than an extra chore.