Harvard Health Letter

Light therapy for conditions other than seasonal affective disorder

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.

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