A reader asks:

I am considering using a light box to adjust my circadian rhythm, which is now severely delayed. I live in an apartment with large windows providing lots of daylight. At night, a nearby parking lot provides some light through my blinds. I recently bought a large sleep mask, as putting up blackout curtains could create problems with my landlord. Is my approach reasonable, or totally illogical?


To correct delayed sleep phase, there are two principles and procedures to keep in mind: (1) Restrict light exposure as much as possible in the evening and at night until about 1.5 hours before wake-up time. (If your wake-up time is in the mid- to late morning, minimizing light exposure will be important throughout early morning.) Before sleep, you want to turn down the lights to a comfortable level for reading or watching TV, but nothing more. During sleep, even low levels of light can be counterproductive, so consider adding dark curtains inside your blinds to block light from the parking lot. (2) Starting at wake-up time, or 1.5 hours earlier, you want to enhance light exposure to counteract your delayed rhythm. Since your bedroom will be dark, you cannot utilize light through the windows.

There are two complementary solutions: First, you can use a dawn simulator for 90 minutes before wake-up time, or simply an appliance timer to turn on bedroom lights. Second, 30 to 60 minutes of bright light box therapy will be helpful when you wake up–a good time for breakfast and reading the newspaper. Over a couple of weeks, move your wake-up time (and light exposure) gradually earlier–say, 15 minutes every three days. Before long, you can expect to normalize your delayed pattern.