There are several clues that light therapy might help people with Parkinson’s disease. Experiments have shown that blocking melatonin might reduce the severity of the muscle rigidity that’s characteristic of the disease — and light therapy seems to reduce melatonin levels.
Light therapy may also help with the depression that besets people with Parkinson’s. Australian researchers enrolled a dozen Parkinson’s patients in a light therapy study. They exposed them to bright fluorescent light (1,000 to 1,500 lux) for an about hour each day shortly before they went to sleep.
Then they assessed the effect of the treatment at regular intervals. Within two weeks they observed improvement in bradykinesia (slow movements) and rigidity. Tremors were not affected, but the researchers did document improvements in mood, sleep, and appetite. Light therapy also permitted the reduction of L-dopa and other medicines without a worsening of Parkinson’s disease, according to the results published last year in a journal called Chronobiology International.
A preliminary study like this one with no control group for comparison can’t be leverage into a treatment recommendation. But, as the researchers noted, it does justify further research into light therapy as perhaps a useful add-on to today’s far-from-ideal treatments for Parkinson’s disease.
Light therapy has also been used on an experimental basis to treat eating disorders. Doctors have noticed a seasonal pattern to bulimia nervosa, the binge eating disorder that often involves compensatory behavior (vomiting, fasting) to avoid weight gain from the binging. Bulimia nervosa patients often get worse during the dark winter months.
Based on that observation and others, light therapy has been tested as a treatment of bulimia in several small studies. In 2001, Canadian researchers reported the results of a four-week study that included 22 female patients with bulimia and seasonal affective disorder (SAD). They received the standard light therapy treatment for SAD: exposure to 10,000 lux light for 30 minutes to an hour each morning.
The good news from the study was that 10 of the 22 women were a lot less depressed after the light treatments. The results for bulimia were good but not spectacular. The “binge/purge” diaries kept by the study volunteers showed that they did binge and purge less often during their month “under the lights.” But only two of the 22 patients stopped the unhealthful eating behavior altogether.
Elderly people in nursing homes are another group that might benefit from light therapy. Depression is a common problem among the institutionalized elderly. The down moods have many causes that have little, if anything to do, with light exposure. But it’s also true that residents in many nursing homes are exposed to very little natural light. And many residents get outside very little, if at all.
Several years ago, University of Texas at El Paso researchers tested bright-light treatment — exposure to 10,000-lux light, 30 minutes daily — in a small study involving just 10 people living in a nursing home. Nevertheless, the results are notable: half of the people were no longer depressed (as measured by a standardized questionnaire) after receiving light therapy.