By Dr. Mercola
For those of us living in the northern hemisphere, the winter solstice and least amount of daylight is fast approaching, as is the risk of Seasonal Affective Disorder (SAD).
An estimated1 20 percent of Americans are affected by SAD each winter, suffering from the blues, fatigue, and in some cases, more serious depression as sunlight grows scarce.
Worldwide, it strikes about 1 in 20.2 What differentiates SAD from regular depression is that a full remission occurs in the spring and summer months. The fact that SAD occurs when 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 4 p.m.).
Scientists generally recommend full-spectrum light therapy over SSRIs like Prozac or Zoloft for this condition, as it has virtually no side effects and is far less expensive than prescription drugs. And, according to recent research, light therapy may be preferable even for major depression.
To learn more about how lighting affects your health, please see my article, “How to Counteract the Ill Effects of Working the Night Shift.”
Light Therapy for Non-Seasonal Depression
The study3,4,5,6 set out to compare the effectiveness of light therapy, alone and in conjunction with the antidepressant fluoxetine (sold under the brand name Prozac).
The eight-week-long 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:
- Light therapy (30 minutes 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 close second, followed by placebo. That's right, the drug treatment was the least effective of all, and LESS effective than placebo!
The mean changes in the Montgomery-Åsberg Depression Rating Scale (MADRS) 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.
Meanwhile, as noted by the authors:
"The combination and light monotherapy were significantly superior to placebo in the MADRS change score, but fluoxetine monotherapy was not superior to placebo. " [Emphasis mine]
Light Therapy Helps Correct Disrupted Circadian Rhythms
At the end of the study, a minimum of 50 percent improvement in symptoms was achieved by:
- Just over 33 percent in the placebo group
- 29 percent in the Prozac only group
- 50 percent in the light therapy only group
- Nearly 76 percent in the active combination group (light therapy plus Prozac)
Remission was achieved by:
- 30 percent in the placebo group
- Just over 19 percent in the Prozac only group
- Nearly 44 percent in the light therapy only group
- Nearly 59 percent in the active combination group
As for why light therapy worked so well, the researchers hypothesize that the improvement was, at least in part, due to the fact that bright light helps reset your biological clock, or circadian rhythm.
Another hypothesis is that by regulating neurotransmitter function, light may work in a way similar to antidepressants. One shortcoming of the study is that they didn't include data on how much natural light exposure people had during the study.
The Importance of Vitamin D
Light therapy lamps like the Carex device used in this study block UV rays, and therefore will not boost vitamin D production, so the results are independent of vitamin D in this case.
That said, vitamin D deficiency has long been associated with both Seasonal Affective Disorder7 and chronic depression.8 For example, one double-blind, randomized trial9 published in 2008 concluded that:
"It appears to be a relation between serum levels of 25(OH)D and symptoms of depression. Supplementation with high doses of vitamin D seems to ameliorate these symptoms indicating a possible causal relationship."
So, if you suffer with either SAD or non-seasonal depression, you'd be well-advised to get your vitamin D level tested. If you're deficient, take steps to optimize your levels to the 40 to 60 ng/ml range.
Light can be shed on the connection between vitamin D and depression when you consider that vitamin D receptors appear in a wide variety of brain tissue, and activated vitamin D receptors increase nerve growth in your brain. It's therefore important for all-around brain function and mental health.
Now, when we talk about sun exposure to optimize vitamin D production, we're really only looking at a small portion of the action spectrum of light, because ultraviolet B (UVB) radiation is the only portion able to photosynthesize vitamin D in your skin.
Natural sunlight contains many other wavelengths, and we've likely only scratched the surface when it comes to identifying the biological activity influenced by the various portions of the sun's light spectrum.
For instance, we know that a whole host of physiological processes are directed by your endogenous circadian rhythm, which is calibrated by exposure to natural sunlight and darkness. And, while daylight as a whole is beneficial to fight off the winter blues, certain wavelengths in the spectrum of sunlight may hold the key to why light therapy works so well for depression.
Blue Light Has Beneficial Effect on Mood
Blue light has been found to be particularly beneficial for boosting your mood — more so than red or green light. While the light used in the featured study included wavelengths between approximately 440 nm and 710 nm (violet, blue, green, yellow, and red light), the impact of blue light on mood could potentially account for some of the benefits seen in this study.
For reference, UVB and UVA, the former of which boosts vitamin D, and the latter of which is associated with skin damage, have wavelengths between 290 and 400 nm. Blue light has a wavelength of about 500 nm, followed by green, and yellow in the 600 nm range.
According to one 2010 study,10 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 and/or treat SAD and depression. 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, researchers have 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 at night should be avoided, as it can impair your sleep. One of the reasons for insomnia and poor sleep is due to excessive exposure to blue light-emitting technologies such as TV and computer screens. The blue light depresses melatonin production, thereby preventing you from feeling sleepy.
In a previous interview, 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, 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."
Eat Right and Exercise
Considering the fact that antidepressants are no more effective than placebo, and in some cases less effective than placebo (as evidenced in the featured study) and come with a laundry list of risks, it would be wise to leave them as a very last resort.
Medical journalist and Pulitzer Prize nominee Robert Whitaker has detailed the many drawbacks and benefits of various treatments in his two books: "Mad in America, and Anatomy of an Epidemic: Magic Bullets, Psychiatric Drugs, and the Astonishing Rise of Mental Illness in America", noting that physical exercise actually comes out on top in most studies — even when compared against antidepressant drugs.
Exercise primarily works by helping to normalize your insulin levels while simultaneously boosting "feel good" hormones in your brain. Researchers have also discovered that exercise allows your body to eliminate kynurenine, a harmful protein associated with depression.11
Restoring health to your gut is also of prime importance. Your gut is literally your second brain, and can significantly influence your mind, mood, and behavior. Your gut actually produces more mood-regulating serotonin than your brain does.
To optimize your gut microbiome, eat real food, and be sure to include traditionally fermented foods such as fermented vegetables, raw milk kefir, kombucha, and others. Ideally, you'll want to start trading out all processed foods for whole foods, and cook from scratch.
My optimized nutrition plan can get you going in the right direction. Refined sugar and processed fructose in particular are known to have a very detrimental impact on your brain function and mental health in general. There's a great book on this subject, "The Sugar Blues" written by William Dufty more than 30 years ago, which delves into this topic in great detail. Cutting out artificial sweeteners will also eliminate your chances of suffering their toxic effects.
Other Factors That Impact Your Mental Health
I also recommend supplementing your diet with a high quality animal-based omega-3 fat, such as krill oil. This may be the single most important nutrient for optimal brain function, thereby easing symptoms of depression. In fact, one 2009 study12 showed that people with lower blood levels of omega-3s were more likely to have symptoms of depression and a more negative outlook while those with higher blood levels demonstrated the opposite emotional states.
Vitamin D, as noted earlier, is another part of the mental health puzzle. Sun exposure is ideal, but if you opt for a supplement, remember to take vitamin K2 and magnesium in conjunction with it. Also, since vitamin D is fat soluble, taking some form of healthy fat with it will also help optimize absorption. Vitamin A, zinc, and boron are other important cofactors that interact with vitamin D. Vitamin B12 deficiency can also contribute to depression, and affects one in four people.
Last but not least, make sure you get enough sleep. The link between depression and lack of sleep is well established. Of the approximately 18 million Americans with depression, more than half of them struggle with insomnia. While it was long thought that insomnia was a symptom of depression, it now seems that insomnia may precede depression in some cases.13
Recent research also found that sleep therapy resulted in remarkable improvements in depressed patients. While there are individual differences, as a general rule, you'll want to aim for about eight hours of sleep per night. The take-home message here is that one or more lifestyle factors may be at the heart of your depression, so you'd be well advised to address the factors discussed in this article before resorting to drug treatment.