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Of mice and mood
December 5th, 2010
01:01 PM ET

Of mice and mood

Douglas McMahon is fascinated by the circadian rhythms of mice.  He spends hours studying them in his lab at Vanderbilt University.  McMahon and his team have discovered something that may provide clues to why humans born in the winter have an increased risk of mood and psychological disorders.

In a study published Sunday in the journal Nature Neuroscience, McMahon and his colleagues took two groups of newborn mice and controlled their exposure to light.  "We were curious to see if light signals could shape the development of the biological clocks," says McMahon, a professor of Biological Sciences at Vanderbilt in a news release.  "Our biological clocks measure the day length and change our behavior according to the seasons."

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For three weeks, one group of mice was exposed to eight hours a day of artificial light to simulate winter.  The other group of mice pups spent 16 hours in light to simulate summer.  Then some of the mice moved to the opposite cycle for 28 days.  The others stayed put.  Once the mice matured, all the mice went into constant darkness.  Researchers tested their brains and measured their circadian cycles to see if the earlier summer and winter light exposure had a lasting effect on their biological clocks.  Biological clocks drive circadian rhythms.

Researchers discovered that early light experience did alter the biological clocks of the mice.  The clocks of the "winter"  ran slower during each cycle.  They also found imprinting changed the way the mice's biological clock reacted to seasonal light change later in life.

"We found that – yes – there were dramatic differences in the way the biological clocks of mice responded to changing seasonal light depending on what their early experience had been," says McMahon.    "Summer" mice behaved the same whether they switched to the winter cycle or stayed on the summer cycle.  However, it was a different story for the "winter" mice. "[They] had clocks that were highly reactive to seasonal change," says McMahon.

So could the biological clocks of these mice explain psychiatric and mood disorders in humans?  Outside experts are intrigued.  "It's quite interesting," says Dr. Charles Raison, an associate professor of psychiatry and behavioral sciences at Emory University.   Researchers have known for years that people born in winter are at an increased risk of mood and psychological disorders, including schizophrenia (though the increased risk is slight).

"Many of these disorders involve disruption of daily rhythms and so it could be that if people born in winter have less stable biological clocks, like the mice raised on winter cycles, then they might be more vulnerable," says McMahon.  He adds the biological clock also interacts with the serotonin system of the brain, which is a key regulator of mood.

Before you start worrying about a loved one born in winter, keep in mind, this research is only in mice.  "We do not yet know if this effect of early light experience  ... that we've shown in mouse babies takes place in humans as well," says McMahon.  Adds Raison, "there are a number of steps between mice and hanging seasonal affective disorder lights on your child's crib to keep them from being schizophrenic."


soundoff (26 Responses)
  1. larry

    It would be interesting to know how much government money was used in this "critical study".

    December 5, 2010 at 14:00 | Report abuse | Reply
    • Evil

      you were born in the winter

      December 5, 2010 at 14:08 | Report abuse |
    • T3chsupport

      I would be interested to find out if, when you hear any sort of interesting information, you instantly wonder how much government money was spent on it.

      December 5, 2010 at 14:37 | Report abuse |
    • Edwin

      larry,

      You consider this a waste because you don't understand it. Research like this can and does change how we understand and treat illness - but short-sighted people like you would block it because you don't see the immediate benefit. People like you would have blocked the research that led to most cancer treatments and the research that led to quicker and better healing of broken bones (amongst hundreds of other things).

      We are lucky to live in a country where *some* people in charge still recognize the value of research. That is one of the reasons American medical science is still one of the best (if not the outright best) in the world.

      Next time you go to the doctor, tell them you don't want any treatments based on 'wasteful' research. They will gladly send you home with two aspirin and a jar of vapor-rub.

      December 5, 2010 at 14:45 | Report abuse |
    • KE

      Plus this study was done by Vanderbilt University if you read the article, not the government.

      December 5, 2010 at 15:46 | Report abuse |
    • Greenie

      Why would you assume any government money was used here?

      December 5, 2010 at 15:52 | Report abuse |
    • realworld

      Because it's a university, Greenie. "The Times Higher Education World University Rankings 2010-11 has listed Vanderbilt as the 51st best university in the world. The university is among the top 10 recipients of federal research funding with $444.3 million in 2008."

      December 5, 2010 at 16:37 | Report abuse |
    • ScienceisgoodforYou

      How much did this cost us? way less than one, single tomahawk cruse missile, way, way less than 1 single day of fighting in Iraq between 2003-2008 (your tax dollars at work too). Guess which has a better chance of helping scientists learn something that might help you or someone you love one day?

      December 5, 2010 at 17:30 | Report abuse |
    • buckup

      Larry- it is a matter of public record. Find out and let us know.

      December 5, 2010 at 23:31 | Report abuse |
    • Valerie

      When a study is funded by grant money from a University or any other post-secondary education system, it comes from the payments to the University by its students, thereby coming from their student loan dollars, or, government money. There are some exceptions to this, such as donations or studies commissioned by Corporations/Companies, etc, but the majority of money funneling into studies ulitmately comes from the government. Whether or not a study is biased or the results are to be expected is up to the individual study at hand.

      December 6, 2010 at 10:24 | Report abuse |
    • vandy alum

      Actually Vandy is LOADED. Vanderbilt is a private university with an endowment out of this world. I doubt government funds were used for this study. Now private grant money??? PROBABLY.

      December 6, 2010 at 12:59 | Report abuse |
  2. Joel

    I was born in November and was wondering if this could be true in humans. I have noticed that my mood changes from good to bad as seasons change.

    December 5, 2010 at 14:52 | Report abuse | Reply
    • LavaJava

      Nope, winter just sucks.

      December 5, 2010 at 15:17 | Report abuse |
  3. JM

    This study is laughable at best. I would dare to say that human children are living indoors where they are exposed to the same type of lighting regardless of their birth month.

    December 5, 2010 at 15:27 | Report abuse | Reply
    • realworld

      Artificial lighting is different from daylight, but what you point out suggests another study: if the earlier data is available compare earlier generations of kids to see how much natural daylight they got in the winter to today's digital kids.

      December 5, 2010 at 16:33 | Report abuse |
  4. dsallen

    I think it's because their birthdays are too close to Christmas and everyone's focused on that, instead. I know we always go out of the way to make a BIG DEAL of our mouse's December birthday...

    December 5, 2010 at 15:30 | Report abuse | Reply
  5. Stosh

    Moody Mice – great name for a band.

    December 5, 2010 at 15:53 | Report abuse | Reply
    • Mouglie00

      trademark the name before someone else does!

      December 6, 2010 at 11:38 | Report abuse |
  6. cool neutral

    The basic biological question here is interesting. Genomic imprinting is relevant to a bunch of diseases and clinical disorders, but let's not overinterpret this study. First, the finding isn't really that novel. Numerous studies have examined how sensory input influences behaviour. Second, mice only live 12-24 months, and their development is nearly, if not entirely, complete within three months, so the 'season' they are born in has a much more dramatic and long-lasting impact on their development. So no, if you were born in November, this experiment has nothing specifically informative to offer you, unless winter lasted 8-10 YEARS after you were born.

    December 5, 2010 at 16:00 | Report abuse | Reply
  7. Teebletat

    Maybe this is why I have a huge increase in mice that have become victim to my cat in the past month, they are the depressed winter born mice that have decided they do not want to be here anymore and have jumped out in front of a cat.

    December 5, 2010 at 16:46 | Report abuse | Reply
  8. keith

    winter makes everyone moody....its not just mice

    December 5, 2010 at 16:50 | Report abuse | Reply
  9. Teri

    What a waste of funds – government funded or not. Whether or not this applies to humans, I can just say this....my ex-husband is the moodiest and most mental person I've ever met in my life (certifiable and diagnosed by a professional). And, he was born in the middle of summer.

    December 5, 2010 at 17:09 | Report abuse | Reply
  10. Free the Leaf

    http://www.facebook.com/free.the.leaf
    cannabis=industry.medicine.peace.

    December 5, 2010 at 17:09 | Report abuse | Reply
  11. Opinioned

    Consider the for instance this research was applied not to just day to day life as we know it, but prolong exposure or development in conditions of this nature, like space or the artic regions; environments where the light was less over a prolong period of time.

    Research don't usually end once a study is done, it sometimes may be instrumental in other research. Our collective knowledge and technology did not start and end with one experiment.

    December 7, 2010 at 19:29 | Report abuse | Reply
  12. Scotty Ajose

    Once regarded skeptically by the experts, seasonal affective disorder, SAD for short, is now well established. Epidemiological studies estimate that its prevalence in the adult population ranges from 1.4 percent (Florida) to 9.7 percent (New Hampshire). Researchers have noted a similarity between SAD symptoms and seasonal changes in other mammals, particularly those that sensibly pass the dark winter hibernating in a warm hole. Animals have brain circuits that sense day length and control the timing of seasonal behavior.^..;^

    Our own website <http://www.healthwellnesslab.com/index.php

    July 3, 2013 at 04:43 | Report abuse | Reply
  13. De'Ana Grogan

    I would love to see that article. Where is the citation, or name of the article that got published?

    September 11, 2013 at 16:41 | Report abuse | Reply

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