11/14/2007 05:22 pm ET | Updated Nov 17, 2011

Moody Blues Have Meaning

It doesn't take a genius to know that being tired makes us cranky, grumpy, and emotional. Not the person your spouse or co-worker wants to deal with today. Blame your foul mood on a lack of sleep first, and the brain second. At last we think we can explain why this is so. Sleep Review journal now reports a study just published in Current Biology that explains how sleep deprivation activates the place in our brains that controls mood.

It's called the amygdala--a group of neurons located deep within a lobe of the brain that helps process emotional reactions. When these nerves get excited (i.e., over-active), which is what happened when sleep-deprived people were shown "aversive" pictures in the study, sleepy people get emotional easily. Those in the study, for instance, were more prone to responding strongly (ahem: moodily) instead of just shrugging off the negative image.

Okay, so now you're wondering what this really means and why it's

important to understand the real connection between drowsiness and

moodiness. This relationship may help us better understand mood

disorders, including bipolar disorder--especially as they relate with

sleep disruption. There's still quite a big mystery shrouding mood

disorders and how, for example, sleep loss can impact how we behave,

act, and even make decisions. This could shed light on evaluating

people in unique jobs like doctors, pilots, and the military who act

hostile or who make bad decisions. Could a focus on their sleep habits

help treat or change them for the better? Can we learn more about

bipolar disorder, which remains a very difficult illness to address, if

we throw sleep studies into the mix?

Most of us have had the pleasure of encountering someone emotionally

irrational. You know the type--the one who is hyper-sensitive and easily

razzed up or angered. But how many of us have thought about how well

(or not) that person sleeps at night?

Something to think about.