Monday, September 5, 2011

Sleep, Light, and Mood Disorder

If you have a mood disorder, whether it's bipolar or depression, you have a sleep disorder.  Your body may make you sleep too much or too little.  You may suffer from insomnia or delayed sleep phase, or you may wake up too early in the morning, exhausted but unable to get back to sleep.  Depending on your medication, these symptoms may be exacerbated.

There's been some interesting research done on this, and a fair bit of evidence has piled up to suggest that "blue light" can be a valuable treatment for mood disorders -- but too much blue light, at the wrong time of the day, can really mess us up.  For this reason, mood expert John Phelps, MD recommends that folks with mood disorders turn off their TVs and computers by 10 pm to reset their circadian rhythms.

Why turn off just your TV's  and computers?  Why not turn off all the lights?

Well, most household lightbulbs produce warm, yellowish light.  TV's and computers need to produce white light in order to render color accurately.  White light, as I'm sure you'll remember from high school physics, contains all the colors of the rainbow, including blue.  It's like from this end of the spectrum that tells you whether it's dark outside.  If you surround yourself with blue light, it tells your brain that it's daytime.

In other words, even if you watch TV in the dark, the light from the TV may well keep you awake.  Reading by the light of an incandescent bulb may not.

I've noticed myself that I can lose track of time when I'm on my computer at night.  I never attributed this to the light it emits; I've always attributed it to my the attention dysregulation that's part of my ADHD.  For this reason, even reading by the light of an incandescent bulb can be dangerous to my sleep.  If I'm reading something really compelling, it will be 4 am before I know it.  This is a tendency I inherited from my mother.  Thanks, Mom!

But here's the odd thing.  I noticed last week that I can get a normal, good night's sleep if I turn off all the lights and read or surf the web with my iPad.  The iPad is a computer screen, particularly designed for media -- it emits plenty of blue light.  Or does it?  Is the screen so tiny that the amount of blue light it emits is trivial?

It's been clear since Week 1 that lamictal intensifies my inborn delayed sleep phase, and makes it difficult for me to change it as I usually can.  I've learned over the years that using my computer late at night makes this worse.  Reading with a small bedside incandescent bulb can also be a problem.  However, using my iPad lets me get tired and fall asleep at a normal hour.  As someone who usually needs to wind down in order to feel tired at night, this is a pretty good thing to know.

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