A reader asks:

I have read that one needs expert professional supervision to synchronize the time of light exposure to your body temperature for effective light therapy. Can you read your body temperature yourself, or is an expert totally necessary? Do you have any suggestions if no expert is available?


First of all, body temperature is NOT the best anchor for timing light therapy, since it is determined by many factors in addition to your internal circadian rhythm. In the laboratory, “core” body temperature is measured by a rectal thermometer that is worn continuously all day and night in order to determine the pattern–not very convenient for patients at home! Oral temperature does not provide an adequate measure. A far better indicator of the internal clock is the pattern of melatonin production by the pineal gland, which lies deep within the brain. Melatonin level can be measured in blood or saliva. However, that, too, is not practical for clinical purposes. To address this problem, CET developed the Automated Morningness-Eveningess Questionnaire (AutoMEQ), which is available free on our website, www.cet.org. The AutoMEQ score closely reflects melatonin timing, and thus provides a circadian time anchor for light therapy.