It is reported that some forms of blindness are also accompanied by loss of circadian rhythms. In spite of these apparently wondrous effects of light therapy, some healthy scepticism is not out of order. Notwithstanding the large number of studies which demonstrate the efficacy of light therapy in treating the symptoms of SAD and the easy acceptance by the public of a condition which appears to explains the dark moods of winter, no properly controlled study has yet been carried out. Double crossover experimental design is the best available, where patient groups are exposed to alternate modes of therapy, and the effects, such as variations in blood melatonin levels, are measured as objectively as possible. Moreover, no satisfactory physiological or biochemical mechanism to explain the effectiveness of bright lights has been demonstrated.
Much work still remains to be done to understand how light therapy modifies our moods.
Nevertheless the finding that a safe, drug-free treatment is helpful in treating a common form of depression has been a great boon to all those who have benefitted from the effects of bright lights.