To Sleep, Perchance to Reset Your Body Clock

Not long ago, I was consulted on the case of an 11-year-old boy with bipolar disorder who was not able to go to sleep before 1 am. The problem did not seem to stem from ongoing symptoms of bipolar disorder. I did not have the benefit of detailed information about the boy’s endogenous circadian rhythms, but I thought a phase-resetting intervention might be helpful. I recommended a 0.3-mg dose of melatonin to be taken daily at 3 pm. For most people, this would be the time when melatonin is most effective in promoting earlier sleep onset (a so-called phase advance). A few days later, to my chagrin, the boy’s parents reported that his condition had worsened! Fortunately, after moving the melatonin dose to 7 pm, there was a marked change in the boy’s bedtime to a more reasonable hour.

What can this case teach us about circadian rhythms and melatonin? And what further lessons do we need about circadian rhythms, light exposure, and melatonin to help our patients with disturbed sleep/wake cycles? To answer these questions, we need to delve a bit into the melatonin and light phase response curves (PRCs) and how they tell us when to use bright light and low-dose melatonin to shift the body clock.

The circadian system

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