I'm not a huge winter fan. I don't like the cold, and I don't like just a few measly hours of sunlight. That's probably why I live in the southwest. But despite that, I still find myself feeling more lethargic in the winter than in the summer. It turns out this is pretty common. More severe cases, involving bouts of depression, is actually diagnosable. It's called Seasonal Affective Disorder (appropriately shortened to SAD). SAD is a mood disorder in which individuals have normal mental wellbeing during most of the year, but then have more "depressive" symptoms in the winter and during times of short-light days.
One culprit of SAD is melatonin, a hormone secreted by the pineal gland, which is located in the brain. It helps control your sleep and wake cycles, like the biological clock and circadian rhythms. It affects your mood and energy levels, and the amount of melatonin produced depends on how much light your body is receiving. In wintertime, melatonin levels are produced usually later in the day than during the summertime. The change in light levels, and thus melatonin levels, can lead to these symptoms of SAD. People, and hamsters, with SAD may be under sensitive to light, unable to perceive artificial light as a longer day during the wintertime.
An interesting fact about SAD: it's not just human-specific; it actually happens to hamsters (and likely other animals), too. I was curious about this because how do you really know if or when a hamster is depressed? After some research, I found that there were a series of experiments done on hamsters back in 2005 at Ohio State University.
Hamsters are thought to be anxious or depressed if they spend more time near the walls of their cages instead of staying in the center; if they forgo sugar water; and if they float in water. Apparently, hamsters don't sink, they float. But if they swim and are active in the water, it's a sign of being content, as opposed to just floating.
In this study, researchers housed both male and female Siberian hamsters in containers that were created to mimic long summer days or short winter days. These were simulated with 16 hours of light and eight hours of light, respectively. After 10 weeks in these containers, hamsters were given the "float or sink test" and then had their brains removed 48 hours later. They were tested for anxiety and depression, seen by hippocampal and cell body size. Researchers said they found their results showed a link between the amount of light hamsters received and their attitudes. The less light hamsters received the more anxious or depressed they were perceived to be. Also, hamsters born in wintertime tended to be more susceptible to SAD than those hamsters born in summertime.
While it is flawed to conclude the same for humans, based on the results of a Siberian hamster, it makes me wonder if there isn't something to the old adage, "go south for the winter," where the days are lighter longer. Let me see if I can find that human study somewhere...
Source: Workman, Joanna L. "Photoperiodic Regulation of Affective Responses and Hippocampal Cell Morphology in Siberian Hamsters" 2005
Image of Siberian hamster from www.asknature.org
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This has definitely been known, albeit anecdotally, for many years. Leaving for work when the sun isn't up and coming back from work when it's already down (and that's just 8-4) then yeah, I'm going to be a bit more depressed. Physical exercise is just about the only thing that I've found helps my mood.
One thing I'm curious about, though, is this sink or float test. I know it's used to test depressive states, but how accurate is this really? It seems like it'd be hard to make a straight comparison between how long a mouse tries to swim with how depressed it is. Several other factors could be playing a role in the outcome. It seems to me like its a very subjective test. Is this test pretty well accepted and are there other test that can give similar results?
Thanks for the article!
It strikes me that SAD might well be simple adaptive behavior in any high-latitude animal. Save energy in the winter, when food is scarce and environmental conditions frequently adverse to survival. The extreme case is of course hibernation, but calling a relatively inactive animal (or person) "depressed" for an adaptive behavior seems a little odd to me. (And I live in Alaska, so SAD is not new to me.)
apparently, it's also true for mice: http://www.medicalnewstoday.com/articles/210639.php
But no sign of human proof...
Lack of sunshine, Vitamin D, is related to SAD.
check out Vitamin D Council.
wonder if those lil' hamsters need some D.
Interesting!
I'd like to point out that, while rare, there is also a summertime SAD.
I studied up on this a few years back (sans hamsters). It seems that humans do better if they get full spectrum light fir a few of those 'dark' hours. I put GE Reveal brand bulbs in ALL of the lighting fixtures in the house, and things seemed to improve. (If this isn't scientifically viable, please don't tell my family, because they BELIEVE it works!)
What works isn't "full spectrum" -- the critical light is a blue-green (think of the color of blue sky through green leaves, a 'daylight' signal).
That's a color that the 'Reveal' bulbs emit; so do halogen lamps, fluorescents, and "white" LEDs (computer monitors and cellphones included).
Timing that on _and_ off matters. For SAD, get that during the daytime; to sleep well, block it at night.
Links to info here, including spectra of different light sources and the research on the receptor and wavelength range.
http://psychcentral.com/blog/archives/2007/03/12/light-and-dark/