A reader asks:

Can one use natural light instead of a bright light therapy lamp?



It’s worth noting that the effectiveness of light therapy, whether bright or natural, is
influenced by individual factors. For instance, the optimal time for light therapy is
determined by your internal clock, which can be assessed using the Morningness-
Eveningness Questionnaire.

Typically, light therapy is prescribed between 06:45 and 08:30, depending on the questionnaire results. The duration is 30 minutes, and a
dose of 10,000 lux of light is the typical dosing regimen, as proven in numerous
successful controlled clinical trials.

For most light boxes, sitting about 30 cm from the
lightbox is recommended to receive 10,000 lux (unless the manufacturer indicates

The question is if natural light can reproduce what the bright light box offers. This
depends on several factors, especially the season, latitude, level of cloud cover, and
whether one is indoors. Most people need 10,000 lux, and you can measure this with
an inexpensive instrument (the TopTes TS-710 Light Meter is recommended by CET).

If one can go outside for a walk or sit on a balcony at the required time for 30
minutes and it’s at least 10,000 lux, then this is an excellent alternative to a light box,
especially in the spring and summer months.

It can be used flexibly with a light box
available when outdoor conditions are impractical.

It becomes trickier when one is
indoors, as a windowpane will significantly reduce the intensity of the light, and it will
depend on where you are in position to the sun rising, as well as your distance from
the windowpane or if you can open the window.

If you prefer this alternative, you
should experiment with your light meter and stick to the minimum of 10,000 lux for 30
minutes at the recommended time when starting treatment and adjust (lower than
10,000 lux, or shorter or longer than 30 minutes, depending on your response).