A reader asks:

 I suffer from delayed sleep phase syndrome (DSPS) and for years have been using a bright light and radio on a timer to wake up. Also, after I started following Ask the Doctor on cet.org, I became much more careful to use dim lights closer to bedtime. These have both been very helpful. (I am also using CET’s ionizer, and although it doesn’t seem to affect my DSPS, it has greatly reduced the chronic congestion I’d been suffering–my wife reports that it has almost completely eliminated my snoring.) Additionally, I have been using melatonin occasionally, but when I use it I take it right when I’m going to bed (usually 6-7 hours before my projected wake time) or if I wake up an hour or two later and am tossing and turning. So I read with interest your recommendation to take melatonin 12 hours prior to wake time. Am I potentially doing more harm than good taking it later than that?


The reason for the earlier melatonin dose is that it reinforces the action of the light in setting your internal clock earlier, thereby making it easier to wake up. This use of melatonin is not as a sleep aid, and for that reason you should use a very low dose (not more than 1 mg) that will not make you sleepy before your bedtime. The potential problem using melatonin when you wake up at night is that it may stay in the bloodstream after wake-up time, contributing to difficulty waking and morning grogginess.