How to Prevent and Treat Seasonal Affective Disorder

Analysis by Dr. Joseph Mercola Fact Checked

Story at-a-glance -

  • Seasonal affective disorder (SAD) is a form of depression that occurs seasonally, typically ramping up in the fall and winter months and disappearing come spring
  • Helpful treatments include optimizing your vitamin D and omega-3 levels, light therapy (including blue light exposure in the morning, but not later in the day), optimizing your sleep, the Emotional Freedom Techniques and exercise
  • Your health and mood are intricately tied to exposure to sunlight. For example, your serotonin levels (the hormone typically associated with elevating your mood) rise when you're exposed to bright light. Your melatonin level also rises and falls (inversely) with light and darkness
  • Vitamin D deficiency is very common, and should be a top consideration when you’re looking for a solution to flagging mood and energy — especially if it occurs during fall and winter months
  • While light therapy can take up to four weeks before you notice improvement, it was shown to be more effective than antidepressants for moderate to severe depression in a 2015 study

The loss of daylight hours during winter is a common cause of seasonal affective disorder (SAD), a type of depression that hits seasonally and lifts as spring and summer rolls back around.

The fact that SAD occurs when the days begin to darken and sunlight is at a minimum is not a coincidence. Your health and mood are intricately tied to exposure to sunlight. For example, your serotonin levels (the hormone typically associated with elevating your mood) rise when you're exposed to bright light.

Your melatonin level also rises and falls — inversely — with light and darkness. When it's dark, your melatonin levels increase, which is why you may feel tired when the sun starts to set, and in the heart of winter, this may be at as early as 3 p.m. if you live far from the equator. Light and darkness also control your biological clock, or circadian rhythm, which impacts hormones that regulate your appetite and metabolism.

As explained in the paper, “Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches,” published in the journal Depression Research and Treatment in 2015:1

“… SAD is a recurrent major depressive disorder with a seasonal pattern usually beginning in fall and continuing into winter months. A subsyndromal type of SAD, or S-SAD, is commonly known as ‘winter blues.’ Less often, SAD causes depression in the spring or early summer.

Symptoms center on sad mood and low energy. Those most at risk are female, are younger, live far from the equator, and have family histories of depression, bipolar disorder, or SAD … Typical treatment includes antidepressant medications, light therapy, vitamin D, and counselling.”

Considering the many health risks associated with antidepressants, and the fact that their efficacy is right on par with placebos, my recommendation is to avoid them if at all possible.

Aside from light therapy and vitamin D, other drug-free treatment options include optimizing your omega-3 level, exercise, the Emotional Freedom Techniques (EFT) and normalizing your circadian rhythm, all of which will be reviewed here.

The Role of Vitamin D

As explained in the featured paper,2 vitamin D appears to play a role in the activity of serotonin, a mood-balancing hormone, and melatonin, a hormone that responds to light and dark.

People with SAD tend to have lower serotonin and higher melatonin levels, which can account for the fatigue, tiredness and depressed mood typically associated with this condition. According to the Depression Research and Treatment paper:3

“A systematic review and meta-analysis concluded that low levels of vitamin D are associated with depression … During the winter months of November through February, those living about 33 degrees north or 30 degrees south of the equator are not able to synthesize vitamin D.

Many people with SAD and S-SAD have insufficient or deficient levels of vitamin D, and although no further studies have confirmed the findings, research investigating this association suggests that taking 100,000 IU daily may improve their symptoms.

Taking vitamin D before winter darkness sets in may help prevent symptoms of depression. Adverse reactions or intoxication is rare but could occur from doses of more than 50,000 IU per day.”

Vitamin D deficiency is very common, and should be a top consideration when you’re looking for a solution to flagging mood and energy — especially if it occurs during fall and winter months.

Ideally, you’ll want to get your vitamin D level tested twice a year, in summer and winter, when your levels are highest and lowest. This will help you fine-tune your dosage over time. While regular sun exposure is the best way to optimize your vitamin D level, this isn’t possible in many areas during the winter, thus necessitating the use of oral supplements instead.

GrassrootsHealth has a helpful calculator that can help estimate the dose required to reach healthy vitamin D levels based upon your measured starting point. The optimal level you’re looking for is between 60 and 80 ng/ml, and for all-around health, you’ll want to maintain this level year-round.

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Omega-3 Fats Are Important Too

Another nutrient that can be helpful is marine-based omega-3. As noted in a 2009 review4 of three studies looking at the impact of omega-3 supplementation on patients with unipolar depression, childhood major depression and bipolar depression:

“Twelve bipolar outpatients with depressive symptoms were treated with 1.5-2.0 g/day of EPA for up to 6 months. In the adult unipolar depression study, highly significant benefits were found by week 3 of EPA treatment compared with placebo.

In the child study, an analysis … showed highly significant effects of omega-3 on each of the three rating scales. In the bipolar depression study, 8 of the 10 patients who completed at least one month of follow-up achieved a 50% or greater reduction in Hamilton depression scores within one month.”

In another study5 published that same year, people with lower blood levels of omega-3s were found to be more likely to have symptoms of depression and a more negative outlook while those with higher blood levels demonstrated the opposite emotional states.

A more recent review,6 published in 2015, pointed out that “Cell signaling and structure of the cell membrane are changed by omega-3-fatty acids, which demonstrates that an omega-3-fatty acid can act as an antidepressant.”

Importantly, this paper also points to research showing that the ratio of omega-3 to omega-6 is an important factor that can influence your depression risk. People with severe symptoms of depression have been found to have low concentrations of omega-3 in conjunction with considerably higher concentrations of omega-6.

You can learn more about the importance of this ratio in “Getting Your Omega-3 to Omega-6 ratio Right Is Essential For Optimal Health.” The key, really, to normalizing this ratio is to increase your omega-3 intake while simultaneously lowering your omega-6 consumption. This means you’ll need to ditch processed and fried foods, as they’re typically loaded with omega-6-rich vegetable oils.

Get Tested Today

GrassrootsHealth, which is conducting consumer-sponsored research into both vitamin D and omega-3, is one of your most cost-effective alternatives when it comes to testing.

Their vitamin D testing kit enrolls you into the GrassrootsHealth D*Action project, where your anonymized data will help researchers to provide accurate data about the vitamin D status in the population, the level at which disease prevention is obtained, and guidance on dosing to achieve optimal levels.

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Their vitamin D, magnesium and omega-3 test kit is another option that will allow you to check the status of several vital nutrients at once. Each kit contains instructions for how to collect your blood sample. You then mail in your sample and fill out a quick online health questionnaire through GrassrootsHealth. A link to your test results will be emailed to you about a week after your blood samples have been received.

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Light Therapy Is More Effective Than Antidepressants

Light therapy,7 using full-spectrum nonfluorescent lighting that has blue light to artificially mimic sunlight, is among the most effective treatment options for SAD. You want to avoid fluorescents as they emit large amounts of dirty electricity. Ideally, have the light exposure in the morning, well after sunrise. As noted in the Depression Research and Treatment paper:8

“Knowing the difference decreased daylight can make in triggering SAD and S-SAD, approaches seeking to replace the diminished sunshine using bright artificial light, particularly in the morning, have consistently showed promise …

Light boxes can be purchased that emit full spectrum light similar in composition to sunlight. Symptoms of SAD and S-SAD may be relieved by sitting in front of a light box first thing in the morning, from the early fall until spring …

Typically, light boxes filter out ultraviolet rays and require 20–60 minutes of exposure to 10,000 lux of cool-white… light daily during fall and winter.

This is about 20 times as great as ordinary indoor lighting … Light therapy should not be used in conjunction with photosensitizing medications such as lithium, melatonin, phenothiazine antipsychotics, and certain antibiotics.”

While light therapy can take up to four weeks before you notice an improvement, it was shown to be more effective than antidepressants for moderate to severe depression in a 2015 study.9,10 In it, the researchers evaluated the effectiveness of light therapy, alone and in conjunction with the antidepressant fluoxetine (sold under the brand name Prozac).

The eight-week trial included 122 adults between the ages of 19 and 60, who were diagnosed with moderate to severe depression. The participants were divided into four groups, receiving:

  • 30 minutes of light therapy per day upon waking, using a 10,000 lux Carex brand day-light device, classic model, plus a placebo pill
  • Prozac (20 mg/day) plus a deactivated ion generator serving as a placebo light device
  • Light therapy plus Prozac
  • Placebo light device plus placebo pill (control group)

In conclusion, the study found that the combination of light therapy and Prozac was the most effective — but light therapy-only came in at a close second, followed by placebo. In other words, the drug treatment was the least effective of all, including placebo.

The mean changes in the Montgomery-Åsberg Depression Rating Scale from baseline to the eight-week end point was 16.9 for the combination therapy (active light- and drug therapy), and 13.4 for light therapy alone.

Blue Light During Daytime Hours May Improve Your Mood

In addition to the bright white light used in light therapy, blue light has also been shown to be useful. According to a 2010 study,11 blue light appears to play a key role in your brain's ability to process emotions, and its results suggest that spending more time in blue-enriched light could help prevent SAD.

Blue light is prevalent in outdoor light, so your body absorbs the most during the summer and much less in the winter. Because of this, the researchers suggested that adding blue light to indoor lighting, as opposed to the standard yellow lights typically used, may help boost mood and productivity year-round, and especially during the winter.

Keep in mind, however, that blue light after sunset or before sunrise should be avoided, as it can disrupt your circadian rhythm. In fact, one of the reasons for insomnia and poor sleep is related to excessive exposure to blue light-emitting technologies such as TV and computer screens, especially in the evening.

The blue light depresses melatonin production, thereby preventing you from feeling sleepy. So, to be clear, you only want to expose yourself to blue light in the morning, and possibly afternoon, but not in the evening.

In “How the Cycles of Light and Darkness Affect Your Health and Well-Being,” researcher Dan Pardi explains the peculiar effect blue light has on your brain, which sheds further light on why it’s so important to expose yourself to blue light during daytime hours only, and why you need to avoid it at night:

"[R]ods and cones in the eye... are specialized cells that can transduce a photo signal into a nerve signal... In the mid-90s, a different type of cell was discovered... [called] intrinsically photosensitive Retinal Ganglion Cells (ipRGC).

It does the same thing as rods and cones: it transduced light to a nerve signal. But instead of the signal going to your visual cortex, it goes to your master clock. Those cells are most responsive to blue light. If you can block blue light, you can actually create something called circadian darkness or virtual darkness.

What that means is that you can see, but your brain doesn't think that it's daytime; your brain thinks that it's in darkness. That is actually a practical solution for living with artificial light in our modern world...

With more awareness, future digital devices will adjust lighting in the evening to automatically dim and emit amber/red light [instead of blue]. This is much better for healthy circadian rhythms and sleep quality."

Address Insomnia

As you can tell by Pardi’s explanation above, the blue light issue is closely related to your sleep quality and circadian rhythm maintenance, and this too is an important component of mental health.

Historically, humans went to sleep shortly after sunset and woke up when the sun rose. Straying too far from this biological pattern will disrupt delicate hormonal cycles in your body, which can affect both your mood and your health. Indeed, the link between depression and lack of sleep is well established, and sleep disturbance is one of the telltale signs of depression.12

Sleep therapy has also been shown to significantly improve depression. While there are individual differences, as a general rule, you’ll want to aim for about eight hours of sleep per night.

For many, this will require going to bed earlier, which can be difficult if you’ve been watching TV or using electronics beforehand, as the blue light from the screen suppresses your melatonin production.

So, an important part of the solution is to avoid screen-time for a couple of hours before bed. Alternatives to not watching TV or using electronics is to install a blue light modulating software such as Iris,13 or using blue-blocking glasses.

Just make sure you don't wear blue blocking glasses during the daytime, which is when you need the blue light exposure. Also, make sure the glasses filter out light between 460 to 490 nanometers (nm), which is the range of blue light that most effectively reduces melatonin. You can easily tell this by looking at a blue light and if it doesn’t disappear with the glasses, it is not blocking that frequency.

Exercise Helps Prevent Depression

Like sleep, exercise can impact your risk of depression. Even a minimal amount of exercise may be enough to combat depression in some people — as little as one hour a week could prevent 12% of future cases of depression, according to one study.14

Participants were followed for 11 years in this study, during which time it was revealed that people who engaged in regular leisure-time exercise for one hour a week, regardless of intensity, were less likely to become depressed. On the flipside, those who didn't exercise were 44% more likely to become depressed compared to those who did so for at least one to two hours a week.

Exercise benefits your brain and mood via multiple mechanisms, including creating new, excitable neurons along with new neurons designed to release the GABA neurotransmitter, which inhibits excessive neuronal firing, helping to induce a natural state of calm15 — similar to the way anti-anxiety drugs work, except that the mood-boosting benefits of exercise occur both immediately after a workout and on in the long term.

Exercise also boosts levels of potent brain chemicals like serotonin, dopamine and norepinephrine, which may help buffer some of the effects of stress. What's more, anandamide levels are known to increase during and following exercise.16 Anandamide is a neurotransmitter and endocannabinoid produced in your brain that temporarily blocks feelings of pain and depression. It can also be activated with CBD products.

Tap for Symptoms of Depression

Last but not least, EFT, a form of psychological acupressure, is a noninvasive way that can help treat symptoms of depression, whether related to seasonal light differences or not.

Some people avoid energy psychology, believing it's an alternative form of New Age spirituality. Nothing could be further from the truth. It is merely an advanced tool that can effectively address some of the psychological short circuiting that occurs in emotional illnesses.

It is not associated with any religion or spiritual outlook at all, but merely an effective resource you can use with whatever spiritual belief you have. In the video above, EFT practitioner Julie Schiffman demonstrates how you can use EFT to relieve your symptoms.

It’s the Season To Be Glad, Not SAD

Since SAD is triggered by the loss of light, it makes sense that light therapy is among the most effective treatments. Vitamin D and/or omega-3 deficiency, as well as lack of sleep and exercise, can also play a significant role, so addressing these basic lifestyle factors could also be what you need to avoid the winter blues.

In closing, it may be worth noting that it's natural for your body to want to slow down somewhat in the wintertime. While this can be difficult when your work and personal life dictate otherwise, allowing yourself to slow down a bit and surrender to the overwinter process may ultimately help you to respect your body's circadian rhythm, and recharge.

That said, this doesn't mean you should plant yourself on the couch for the winter and not venture outdoors. On the contrary, staying active and spending time outdoors during the day are among the best "cures" for SAD.