Light therapy (phototherapy) is more widely used to treat Seasonal Affective Disorder, but it is also an effective method of adjusting sleep/wake timing. The principle behind it is that exposure to light in the morning advances the sleep phase, whereas light in the evening delays it.

For light therapy, you need a source of very bright light. Room lighting is not bright enough. Sunlight is good, if you have lots of windows or if you can get outside. You should never look directly at the sun, of course. Most convenient is an electric light box or light visor, available from some medical supply stores or by mail-order. A good light source will have the UV radiation filtered out. Remember that the intensity of light drops off exponentially with distance from the source. For example, if you double the distance between the light source and your eyes, the dose you receive is reduced by 75%. Treatment effectiveness also increases (up to a point) with the length of exposure – 30 minutes to two hours is often recommended.

Advantages of Light Therapy

• The light levels in commercial light therapy equipment are believed to be safe for eyes, at least in the short term and for people who do not already have eye disease.
• Does not require taking time off work or school.
• Light therapy daily or a few times a week is a simple way to maintain your sleep schedule once you have moved it to an earlier time.

Disadvantages of Light Therapy

• Certain medical conditions and medications are incompatible with light therapy. Check with your doctor if you are taking any kind of medication, or have any skin or eye disease.
• Headache is a possible side effect. It may help to avoid reading or having to focus your eyes during the light exposure. and to decrease the intensity of the light.
• Overdosage can make you feel “wired” and overstimulated – if this happens, decrease the time or intensity of the light treatment.
• The long-term effects of bright light treatment are not yet known.
• You can do other things in your morning routine while under exposure to light, but you may still need to wake up earlier than you normally would, so you can get enough light before leaving the house in the morning. You don’t have to get out of bed for light therapy, as long as you keep your eyes open.
• Equipment for light therapy can cost several hundred dollars (Canadian or US). If you have a doctor’s prescription for light therapy, and extended medical insurance, your insurance plan may cover it.
• Requires some time – a few days to two weeks – to take full effect. During this period, you will probably feel sleep-deprived.

Timing of Light Therapy and Sleep

Light exposure timed just before the middle of the night is most effective in delaying the sleep phase, and light timed just afterwards is most effective in advancing it. In this case, “night” refers to your night, so if you are used to sleeping between 4 am and noon, the middle of the night is around 8 am (give or take about an hour). The general rule is that light therapy for DSPS should begin as soon as you can get up in the morning. Minimizing your exposure to light in the evening may also be helpful.

There are different ways you can reschedule your sleep with the help of light treatment

1. Cold-turkey phase advance. That is, if you want to be getting up at 7 am, you force yourself up at 7 am, and don’t take naps, every day until (you hope) you get used to it. Light therapy upon waking should accelerate the adjustment.
2. Gradual phase advance. This means getting up a little earlier, e.g. by 15 minutes, every day or every other day, until you reach your desired wakeup time. It can take a long time if you are more than two hours away from the schedule you want.
3. Sleep deprivation-phase advance (SDPA) consists of staying up all night then moving bedtime one or 1.5 hours earlier the next night. If you are more than 1.5 hours away from your desired schedule, you can do this once a week on the weekends until you’re there. SDPA doesn’t always work – some DSP individuals cannot fall asleep until their normal bedtime even after staying up all night.
4. Cold-turkey phase advance with a nap. This involves getting up early for light therapy and going back to bed for a nap after the light treatment is over. You will probably find it easier psychologically to wake up early if you know you can go back to sleep again soon.