SAD, or seasonal affective disorder, is a type of depression that sometimes is treated with bright light therapy. Do the devices often known as SAD lamps or light boxes really work?

Psychologist Michael Terman has the scoop, as he specializes in “chronotherapy,” which involves determining treatment for such issues as SAD via analyzing one’s unique body clock or biorhythms. On his blog he writes, “By now the question is settled. Light therapy for depression and delayed sleep phase can achieve remarkable improvement. In speed of action and ultimate outcome, it can beat antidepressants and sleeping pills.”

But don’t just buy any old SAD lamps on the market, he warns. Many of these devices haven’t been thoroughly tested and could either cause or contribute to serious health problems.

Even if you pick a good one, how can you be sure you’re using it right? In another post Terman advises finding a specialist in light therapy, as there are various things to consider: “The primary dosing parameters of light are its field of illumination, intensity and spectral content (even within variations of white), and the length of exposure sessions. But the ultimate effect depends heavily on when you use the light within your own particular circadian cycle, as reflected in your chronotype.”

Did you understand that? If you need an interpreter for the above couple sentences (guilty), all the more reason not to decide on your own whether or how to use light therapy, or SAD lamps. (Or melatonin, it turns out.) (More on this below.)

What if you can’t find a chronotherapist or light therapy specialist? (I’m guessing this to be a common glitch.) Terman, along with psychologist Ian McMahan, has written a book that covers the essentials—Chronotherapy: Resetting Your Inner Clock to Boost Mood, Alertness, and Quality Sleep (2012).

Depression and sleep problems often co-occur in a “frustrating cycle,” indicates the book’s publisher. More from the Chronotherapy description:

…Terman helps readers decipher when their natural internal night begins and ends. The treatment process can then start, incorporating the power of natural light and, when necessary, supplemental light therapy. His approach has brought relief to thousands of sleep sufferers, as well as those burdened by bipolar disorder, seasonal affective disorder, depression, sleep disorders due to around-the-clock work schedules, and other impediments to vibrant health. For the first time, his findings are now available for a general audience, sharing the essential elements of chronobiology in clear, authoritative, scientifically grounded chapters that are easy to apply to a variety of situations.

Susan Adams, Forbes Magazine: “The authors’ breakthrough message: Once we understand how our circadian rhythm affects our lives, we can control some environmental factors and cure ourselves of insomnia, fatigue and depression.”

In addition to the specific kind of light therapy the authors recommend, Adams notes this interesting fact about the use of melatonin:

The authors say that popular over-the-counter melatonin tablets are no good as sleep aids. The usual drugstore dose of 0.5, 1 or 3 milligrams, puts a much higher level of the hormone into the bloodstream than the body would ever produce, they write. But the authors like melatonin as a tool to set the circadian clock, and they have developed their own low-dose, controlled release tablet that, together with light therapy, works well, they say.