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Rats get SAD, but backwards.

Most people are aware that the shorter days of winter lead to less sunlight exposure and can cause depression-like symptoms known as seasonal affective disorder, or SAD, but they probably aren’t aware that this process is reversed in rats.

New research from the University of California, San Diego, has found that actually rats experience increases in depression and anxiety when the days grow longer. Of greatest importance is the discovery that large changes in the day and night cycle cause a new chemical code to be adopted by the rat’s brain cells, allowing an entirely different neurotransmitter to stimulate the same part of the brain.

Read more at University of California San Diego

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  1. Caroline Copley


    Living in the southern hemisphere and watching the supermoon on the shortest day one can only reflect that now the Sun is coming back the weather will get colder, yes winter is worse here as the Sun is returning, so there is some kind of weather lag that I am sure the meteorologists could explain to me, or I could look up on Google.
    But in examining animals, although a similar weather lag could be involved, we must remember that well, most of them in Australia, are nocturnal. Therefore longer days are probably a disadvantage and mean less food intake rather than more.
    Good research though, reminds us that nothing is ever as straightforward as it seems in Nature.

  2. Caroline Copley


    Sorry hadn't read the article, now of course I realise that you point out that the rats are nocturnal! Still, the weather lag may apply. Also interesting that the mechanism is hormonal. Hormones seem to be the stuff of life. Also interesting about the same neurons switching neurotransmitters. Nature is efficient, or lazy, depending on spin. Why double up if you don't have to?

    With the stress effect versus photoperiod, if you severely stress the rat which would be mean of course (!) no doubt there might be some effect. But generally my guess would be photoperiod would win out as causation for the hormonal switch.
    And I would also be willing to bet you Aust10c that the ratio will be 60:40. Why? Aha, my thought is along the lines of if the entropy in the universe were wildly greater than the order, we'd all be in trouble, so that the ratio of light effects to dark effects are likely to be close e.g. 60:40. Just a guess mind you.