My formerly sleeping-through-the-night toddler has, well, gotten out of that habit a bit.
Gone are the nights that she goes to sleep before 8 pm and I don't hear a peep until the 5 am hour.
"Those were the days ... "
There were several hints that she was becoming afraid of the dark. One was the screaming. Others were: the complete hysterics at being left alone in a dark room if she wasn't back asleep, the need to be touching mommy constantly in a dark room if brought to mommy's bed in the middle of the night, and the complete inability to soothe herself back to sleep in a dark room.
Friday night I left a light on in her room, and she woke up once, soothed herself back to sleep, and slept until 5:30. Hurrah!
So I am now in the market for a night-light. Given the crib light that I left on for her will probably burn out very soon, we will need a professional night light to continue the job.
Now, in case you missed it, I teach physiology for a living. I love my job - but I hate knowing stuff sometimes.
A structure in your brain (the pineal gland) secretes a hormone called melatonin. This hormone, among other things, helps to regulate your circadian rhythm, and helps with sleep-wake cycles. The protein synthesis process is light-sensitive: when light comes in through the optic nerve, the production of melatonin is suppressed. When light is not coming in through the optic nerve, melatonin can be made. It makes you sleepy, which is why you want to sleep at night.
There is lots of cool stuff you can do with this information. You can help shift workers not be sleepy at night, and instead be sleepy during the day. You can help shift people's circadian rhythms so they recover from jet lag faster. All by manipulating the timing of light in the eyes and the amount of melatonin produced.
This is also one reason they tell you not to turn on bright lights when you get up in the middle of the night, and why they think exposure to bright computer screens in late evening disrupts people's sleep cycles - see here for some evidence of that.
So I'm concerned about a night light. I had a very hard time getting her sleep-wake cycles regulated when she was a newborn. She liked to sleep during the day and nurse all night long. So I'm concerned that exposure to light at night will suppress the melatonin that her brain needs to (a) know that it's nighttime and (b) sleep.
I found several really cool night lights. One is a clock and a night light, with a color feature so you can teach your child not to get out of bed until it turns green (OMG I might actually be able to sleep until 6 am on a Sunday someday?)
So to satisfy the inner scientist, I started doing more reading. This is an interesting article looking at different wavelengths and irradiances of light on melatonin production. Now, while I understand the physiology, I don't understand the physics. I believe that irradiance is a measure of brightness, but I could be wrong on that. At any rate, I think what the results show is that brighter light suppresses melatonin more than lower intensity light, and shorter wavelength light had more effect than longer-wavelength light, which is also what the first abstract showed.
(This psycho just has too much time on his hands - but it's an interesting read if you're interested in night light processing by retinal cells.)
So I reassured myself that a night light might be okay as long as it isn't a blue light, as long as it is green or longer wavelength. This night light clock glows yellow, so I think that's far enough away from the blue light length on the spectrum so it won't disrupt her sleep too much.
As long as it helps her not be afraid and to soothe herself back to sleep, I'm in.