Armour & Patton write a helpful review on the use of Melatonin in children (Psychiatric Bulletin, June 2004, 28, 222-224). Several studies they mentioned were with blind subjects. It is important to consider that blind people have free-running circadian rhythms that are not amenable to the most powerful of resetting cues - light. The use of melatonin to trigger the new 24-hour period is very powerful in this population (Reference Sack, Brandes and KendallSack et al, 2000).

Lewy et al (Reference Lewy, Emens and Sack2002) showed that low levels of melatonin, 0.5 mg, reset rhythm but not high doses, 2 mg. The prolonged half-life of melatonin and the sensitivity of the circadian rhythm to its presence mean that in trying to achieve phase advancement (bringing sleep forward to combat ‘sundowning’ in the elderly) or delay (delaying sleep onset to combat ‘jetlag’) melatonin has a window effect. Too low a dose and no effect, too high and the chronobiologic effects are lost and the direct somnolent action is experienced. It would be a shame if a potentially useful treatment for circadian rhythm disorders, including sleep disturbances and seasonal affective disorders, were discarded prematurely due to a perceived lack of efficacy.