In the early 1980s my colleagues and I found that the symptoms of winter depression could be greatly alleviated by exposing the SAD sufferer to bright environmental light. Many controlled studies have by now demonstrated beyond question that light therapy is an effective treatment for this condition. Light therapy has been accomplished most successfully by means of special light boxes or fixtures. A typical light box is a square or rectangular metal apparatus that contains fluorescent light tubes behind a plastic diffusing screen. The user generally places it on a flat surface, such as a desk or table top, and sits a certain prescribed distance away from it. In order for light therapy to be effective, the user’s eyes must be open, but it is not necessary to stare at the light. Instead, people often choose to read, eat their meals or do anything that can be done while sitting in one place. I used to recommend that people use this time for paperwork or chores, but then I found that they were avoiding doing their light therapy because they associated it with unpleasant matters. So now I advise them to do whatever will succeed in helping them to use their light therapy regularly throughout their winter depressions. Just as with anti-depressant medications, if a person is still in a vulnerable phase, for example during the short dark days of winter, light treatment must be continued even if symptoms are under good control in order to avoid a depressive relapse.
Light boxes may stand upright or be tilted forward, an arrangement that reduces glare and brings the light source closer to the face, resulting in greater amounts of light entering the eyes. Light intensities are measured in units called lux. Average indoor lighting is about 500 lux; modern light therapy fixtures result in levels of approximately 10,000 lux, about 20 times as much light as ordinary indoor lighting provides. Properly designed light boxes include special filters that remove potentially harmful ultraviolet rays from the light source. If used as recommended, light therapy appears to be very safe and, out of thousands of people treated with light therapy over the past 15 years, no evidence of any harm to the eyes has been reported. Even so, if you have any history of eye problems you should have your eyes checked out by a qualified professional before initiating light therapy, as some serious conditions of the retina can be exacerbated by exposure to bright environmental light.
The duration of light therapy needed varies with the time of year and the individual, and depends also on what is convenient and feasible. The worst elements of the depression can often be prevented if the problem is tackled early in the season. During the autumn or early winter, just before the usual time of onset of symptoms, it is reasonable to begin with 15 to 30 minutes of light therapy in the morning. Studies have shown that light therapy can be most effective when given in the morning hours, though many people find it to be beneficial no matter when they use it during the course of the day. I therefore often recommend that people start by using light therapy whenever it is most convenient. As the winter deepens, it is often helpful to add a second dose of light (such as 15 to 30 minutes in the evening) to the morning dose. After using light therapy for some time, people often become skilful at calculating how much works for them. Some people require up to 45 minutes of light therapy twice a day in order to obtain optimal effects. This amount of light therapy might seem like a very burdensome time commitment, but it is important to remember that one is often sitting down in one place anyway, and it is often quite convenient and actually pleasant to have the bright, cheerful light of the box shining down on you while you are doing so.
Just as people often learn how much light they need in order to overcome winter’s doldrums, so they frequently learn to detect when they are being exposed to too much light. Side-effects of excessive light treatment include feelings of restlessness and overstimulation, headaches or eyestrain. These effects frequently respond to decreasing the duration of light exposure or sitting a little further away from the light fixture. Using light therapy late at night may cause difficulty falling asleep, in which case it often helps to move the light therapy to an earlier hour during the evening or late afternoon.
When spring arrives, people naturally find themselves using their light boxes less and not missing them. But spring tends to be an erratic season and it is prudent to watch out for rainy or cloudy days – especially a string of them – and be ready to bring out the light box at a moment’s notice.
An innovation developed to help people who want to move around while receiving their light therapy is a head-mounted light delivery system called a Light Visor. This device is also handy for those who need light therapy while travelling. While many people swear by the benefits of the Light Visor, data from controlled studies of the anti-depressant effects of light therapy are not as convincing for the Light Visor as for the light box.
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