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Genetics and Seasonal Affective Disorder

Key takeaways:
~ Seasonal Affective Disorder (SAD) affects 5-10% of the population in higher latitudes.
~ Genetic variants in circadian rhythm and light detection genes are linked to increased susceptibility to SAD.
~ Changing your lighting may help you beat the winter blues.

This article dives into the science of why seasonal affective disorder occurs, which genetic variants increase susceptibility, and the personalized solutions that may work for specific genetic variants. Members will see their genotype report below, plus additional solutions in the Lifehacks section. Join today 

What is Seasonal Affective Disorder?

The Winter Blues… It’s often described as feeling low, generally apathetic, blah, usually accompanied by changes in sleep.

Officially called Seasonal Affective Disorder, the change in mood when the days grow short is a fairly common phenomenon in higher latitudes. It affects 5-10% of some populations.[ref]

Seasonal Affective Disorder (SAD) is characterized by recurrent depression with a change in the season, usually in fall/winter for most people.

Scientists think SAD is due to an aberrant or altered response to light. It could be due to not enough brightness from sunlight or simply not enough hours of light.

SAD is considered to be highly heritable, and studies in twins show that about 50% of the risk is genetic.[ref] What is the other half of the equation here? Daylight exposure is a big one. Chronic inflammation may also increase the risk.

Researchers can determine what causes a problem – the root cause – by finding out which genes enhance the likelihood of a disease or disorder.

Knowing the genes involved can help us understand which biological pathways are involved.

For seasonal affective disorder, research pinpoints many genes that encode circadian rhythm proteins.[ref]

Circadian rhythm and SAD:

Our circadian rhythm is controlled by genes triggered by light hitting the retina of our eyes.

During the daytime, light in the blue spectrum hits specific receptors in the retina and shuts off melatonin production from the pineal gland. This process occurs when blue light hits a specific receptor (OPN4), triggering a signal to the brain to stop melatonin from being produced.[ref]

At night, the lack of light in the blue wavelengths allows melatonin levels to rise again.

Both the suppression of melatonin during daylight via exposure to bright light and the rise of melatonin at night due to darkness are integral to mental and physical health.

The lack of light during the daytime may affect seasonal depression by not shutting off melatonin production enough during the day.[ref]

Interestingly, some genes associated with SAD also overlap with genetic variants that increase susceptibility to bipolar disorder and schizophrenia but not other depressive disorders.[ref] For many, bipolar disorder is linked to circadian rhythm disruption.

Related article: Circadian rhythm genes and bipolar disorder

The core circadian clock genes include a pair of genes (CLOCK and BMAL1) active together during the daytime and another pair of genes (PER and CRY) active during the nighttime.

The rise and fall of these genes create a 24-hour molecular clock that governs many cellular functions throughout the body.

Messing up your circadian rhythm makes you feel bad…

If you have ever traveled across several time zones, you know that jetlag can make you feel a bit wretched for a day or two. For me, jetlag makes me feel disoriented, grumpy, and unable to think clearly.

The feelings of jetlag are due to your circadian clock being out of sync with your environment. Your body thinks it is midnight, but your eyes know that the sun is up and shining brightly.

When your circadian rhythm is disrupted — whether from travel or staying up late, or changing light — the result can cause physiological changes in how your body feels and your mind works.

Serotonin and SAD:

You may be wondering, but what about serotonin? Everyone thinks of serotonin for depression due to the popularity of SSRIs as antidepressant drugs.

Several studies for seasonal affective disorder have looked into the link to serotonin. While most of the studies didn’t find a significant link to serotonin genes, the way serotonin is used in the brain may play a role in SAD.[ref][ref][ref] For example, certain behaviors linked with seasonal depression, such as overeating, may be related to serotonin.[ref]

Interestingly, a couple of studies have found that a serotonin receptor, HTR2A, is significantly associated with seasonal depression in both winter and summer. This receptor involves memory, mood, cognition, appetite, anxiety, perception, sleep, thermoregulation, and vasoconstriction. It is activated by serotonin, LSD, psilocybin, and DMT.

Related article: Serotonin receptor 2A genetic variants

Is there a SAD gene?

While genes do play a major role in increasing the risk of SAD, there is not one specific gene mutation that causes seasonal affective disorder.

Instead, multiple genetic variants add to the risk, along with latitude, length of daylight, and possibly dietary factors.

Additionally, seasonal changes occur in most mammals to neurotransmitter levels.

Monoamine Oxidase (MAO-A) Levels change seasonally

MAO-A is an enzyme that breaks down neurotransmitters, and changes in MAO-A levels are linked to depressive disorders.

Recently, researchers discovered that most people normally have a seasonal change in MAO-A levels in the fall and winter. But people with SAD don’t have that normal, seasonal rhythm to MAO-A levels. Important here, the researchers also found that bright light therapy restored the normal MAO-A seasonal dynamics.[ref]


Seasonal Affective Disorder Genotype Report

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Lifehacks for Seasonal Affective Disorder

First and foremost: going outside first thing in the morning may help if you live at a middle latitude. The morning sun is powerful in resetting your circadian rhythm.

Both light and dark are important:

Light Boxes for Full Spectrum Light:
If you can’t get outside for enough sunlight during the daylight hours for whatever reason (working, living too far north, etc.), there are full-spectrum lights made specifically for SAD. Studies have found 30 minutes of 10000 lux in the early morning effective.

New studies show that narrow-spectrum blue light (100 lux) may be as effective as bright full-wavelength light (10,000 lux).[ref][ref]

Putting a blue light in your ear may sound a bit ‘out there’, but there are a few studies that indicate this might just be something worth trying. A clinical trial of transcranial blue light through the ear canal reduced depression by half in more than 75% of participants.[ref] (I’m not sure how great this clinical trial is, though, since there is no sham or control group, just comparisons of different light strengths.) Transcranial light isn’t as crazy as it seems. Animal studies have shown that extra-ocular light (i.e., through the ear canal) has an effect on the brain. Birds are known to have photoreceptors in their brains that regulate seasonal reproduction.[ref] Sunlight through the skull induces GABA release in rats.[ref]

Sleep in the dark:
A mouse study looking at the effect of dim light at night found that for mice lacking in PER3 (similar to the above genetic variants), dim light at night caused an anhedonia-like effect.[ref]

Anhedonia is the loss of pleasure or interest in things, feeling blah. Nighttime light exposure has become an enormous problem worldwide, with far-reaching health effects on people and animals. If you have PER3 genetic variants (or even if you don’t!), blocking light at night is essential for healthy sleep.

Blackout curtains are not that expensive, and you can block all the little LED lights from chargers, etc., by just putting a piece of dark tape over them.

One huge change we all face in our modern times is large amounts of blue light at night from TVs, tablets, and cell phones. Turning off electronics an hour before bedtime is helpful for naturally increasing melatonin production at night. Alternatively, blue-light-blocking glasses that eliminate 100% of light in the blue wavelengths may also help improve sleep.

Dietary links to seasonal affective disorder:

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Why join Genetic Lifehacks?

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~ You'll see your genetic data in the articles and reports.

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Related Articles and Topics:

Serotonin: Genetic variants that impact serotonin levels and serotonin receptors
Serotonin is a neurotransmitter that is important in depression, sleep, and many other aspects of health. Learn how your genetic variants in the serotonin receptor genes impact their function.

COMT Gene: Neurotransmitters, estrogen metabolism, and more
Wondering why your neurotransmitters are out of balance? It could be due to your COMT genetic variants. The COMT gene codes for the enzyme catechol-O-methyltransferase, which breaks down (metabolizes) the neurotransmitters dopamine, epinephrine, and norepinephrine.

 

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About the Author:
Debbie Moon is the founder of Genetic Lifehacks. Fascinated by the connections between genes, diet, and health, her goal is to help you understand how to apply genetics to your diet and lifestyle decisions. Debbie has a BS in engineering from Colorado School of Mines and an MSc in biological sciences from Clemson University. Debbie combines an engineering mindset with a biological systems approach to help you understand how genetic differences impact your optimal health.