For many (myself included), the steady progression towards shorter days and colder weather means a couple of things: a chance to bust out the ‘ol’ scarves and sweaters, WINTER BREAK, and seasonal flavored drinks. Lots and lots of seasonal drinks. As far as I’m concerned, the rest of the year after winter is just a long countdown to the next year’s fall. Yet, these joys of fall and winter don’t seem to permeate through the dense, sharp cold for everyone in quite the same way.
For some, the sunless days are just that — a muted version of summer days now devoid of light and all joy. Believe me, this is not just because summer break is over and people are dreading the start of coursework mundanity. Well…okay, maybe there’s a little bit of that in play. But for around 5% of the US population, there really is a justifiable reason for feeling low.
Aptly named “winter seasonal affective disorder (SAD)”, this form of depression frequently affects those in their twenties. Mhmm, that’s right. People our age. Of course, other contributing factors include whether or not you have a family history of depression and your location relative to the equator. If you’re confused about that last part, fret not. I’ll explain it all in due time.
We may each spend our 24 hours differently; perhaps it’s an intense study day at Geisel or maybe it’s time to head to La Jolla Cove for some much needed seal-watching. Whatever you end up doing with your time is really up to you. But I can say with 100% certainty that there is one part of the day that we all share: light.
Can You See The Light?
As is often the case, our fluctuating mental states can be traced back to the microscopic mechanisms of the brain. Those who have fallen victim to SAD can blame their bleak outlook on life on a mishap in the brain’s natural response to the external environment.
The level of light during the day tells us when it’s morning, when it’s noon, and when it’s evening. It’s kind of like the environment’s way of helping us keep track of time. And in fact, this has even greater consequences for us than one may imagine.
In response to the light levels of the environment, our bodies have developed a circadian rhythm — physical, mental, and behavioral changes — that follow a 24-hour cycle. This cycle is an integral part of our health as it directly influences our sleep-wake cycles, hormone release, body temperature, and so on.
The Neural Network
So how exactly does the whole circadian rhythm thing work? The body’s “master clock” is the answer. The suprachiasmatic nucleus (SCN), is located in the hypothalamus, just above the place where the optic nerves from our eyes cross.
It makes sense for the SCN to be located here too, since it has a direct link to both the environmental light levels that enter our eyes and to the hypothalamus, a regulator of our body’s hormones and neurotransmitters, chemical messengers that allow for the transmission of signals from one neuron to the next.
One particularly important neurotransmitter to the circadian rhythm is serotonin, whose main role is to modulate the circadian rhythm’s sensitivity to light.
Now here’s the fun part. Researchers from The University of Copenhagen ran a study in which the positron emission tomography (PET) brain scans of those with SAD were compared with the scans of those with healthy brains. The results showed a significant difference in the levels of the serotonin transporter protein from summer to winter in the participants with SAD.
While those without SAD have “normal” levels of serotonin regulation throughout the winter months, those that are diagnosed with the disorder experience a deficiency of serotonin. This leads to a domino effect within the brain. Less serotonin affects the circadian rhythm, which in turn affects our sleep, hormones, and other body processes.
The Break Down
I know it hasn’t really gotten too seasonal here in San Diego, but I can’t help but anticipate the change as I walk down Library Walk and feel the unpleasant 85 degree burn from the SoCal sun above. I admit that it’s mildly unsympathetic of me to go through this whole spiel about the cause and effect of the Seasonal Affective Disorder and then revert to my original sentiments of a faster transition into winter, but San Diego likely won’t become too sunless in the upcoming months.
This is why the equator is so important to those with SAD. As it turns out, those that live farther from this imaginary line on the earth’s surface, so farther north or south, have a higher chance of developing depression due to SAD than those that live nearer to the equator. This is simply due to the fact that there is a greater change in light for these northerners and southerners. During the summer, the days are much longer in comparison to days in San Diego, and the winter months have significantly lower light levels.
Check out how light levels around the globe change with the seasons here.
For those who do live in the further northern and southern hemispheres, fear not. SAD can be treated in a number of ways such as with light therapy, psychotherapy, and medication.
Since this form of depression is due mostly in response to environmental light levels, patients have been treated with light therapy. Also known as phototherapy, this form of treatment involves sitting in front of a light therapy box that exposes the patient to bright light, essentially mimicking natural outdoor lighting in the hopes that it will trigger the SCN into producing more hormones to readjust the circadian rhythm.
Of course, other treatments include antidepressants and psychotherapeutic sessions, which help the patient learn to cope and live a productive life with depression.
Another way to prevent feeling down is to go out and enjoy the sun. This advice is actually good for everyone, whether you have depression or not. And hey, if you still play PokémonGo, there’s even more motivation to catch ‘em all.
Watch the American Chemical Society’s take on SAD in their YouTube series, Reactions.