The dark days of winter bring risks for brain health

The major link between dementia and winter depression. Plus, the simple, low-cost solution.

During winter in the Arctic and Antarctic regions, the sun completely disappears below the horizon for months at a time. Some people who experience this phenomenon suffer from a mental disorder known as “arctic hysteria.” The Eskimos call it “piblokto.”

In Canada and the northern U.S., folks nonchalantly refer to this mental condition as “cabin fever.” But whatever term you use, there’s scientific evidence that not seeing the sun for extended periods of time can trigger mental changes, ranging from dementia to depression.

And a lot has to do with a lack of vitamin D.

Darker days can trigger dementia

During the dark days of winter in many parts of the northern hemisphere, your body is unable to produce enough vitamin D from sunlight exposure.

That’s because the sun doesn’t get high enough in the sky for the proper wavelengths to penetrate through the atmosphere to activate D in the skin.

And that’s a real problem, because in addition to its benefits for the body, D has a profound effect on the brain.

I recently reported on a new study of nearly 3,400 people from Canada, France, and the U.S. About 20 percent of the study participants had Alzheimer’s disease, and the rest were cognitively healthy.1

The researchers found that new cases of dementia and mild cognitive impairment in study participants were 30 percent more likely to occur in winter and early spring. The participants (including the ones with Alzheimer’s) also performed significantly worse on cognitive tests during the same time of year.

And yet, somehow, the researchers couldn’t seem to figure out why.  They considered every cockamamie explanation, except for the most obvious one—that vitamin D blood levels start to get lower in most people after the summer and early fall. 

Meaning that the study participants likely had their lowest D levels of the year during winter and early spring. This makes perfect sense considering that all the participants lived in areas where there’s not enough winter sun present to help the skin make vitamin D.

Winter-related depression

Vitamin D also has an effect on mood, and deficiency can make you feel blue. Indeed, experts now recognize that low sun exposure causes seasonal affective disorder (SAD) in millions of people.

SAD can be difficult to distinguish from typical depression, but there are some specific signs. If you’re feeling depressed during the winter months, have low energy, sleep too much, have difficulty concentrating, crave carbs, and are gaining weight, you may have SAD.

Mainstream medicine cites various reasons for SAD, including a family history of depression.

I guess we shouldn’t be surprised that low vitamin D levels are often at the bottom of their list. Even though the common treatment for SAD is to sit in front of a therapeutic light box (also called SAD lamps, or light therapy boxes) for a half an hour every day after waking up. They emit either yellow or white filtered ultraviolet light and can be found on

Considering the reams of scientific evidence showing that vitamin D can help prevent or manage other types of depression, it certainly makes sense that daily D supplementation may also help improve SAD symptoms.

Other D-related mental disorders

Unfortunately, SAD may be just the tip of the iceberg when it comes to the more prevalent winter-triggered brain and mental disorders. Research also links vitamin D deficiency with schizophrenia and other major mental illnesses.

Scientists in the United Kingdom (which is too far north for winter vitamin D activation) recently published a study of 69 people with major psychosis (such as schizophrenia) and 69 people without.

The researchers made special note of the vitamin D levels in the people after their first psychotic episode. In other words, the researchers wanted to see if the patients had low vitamin D when they first experienced their mental illness.

Other studies have shown that psychotic people at in-patient facilities frequently suffer from low vitamin D.

But this study used blood samples taken directly after the patient had first been diagnosed with a mental disorder.

Overall, the researchers found that the study participants with psychosis had significantly lower levels of vitamin D during their first psychotic episode. In fact, the psychotic patients were almost three times more likely to have a vitamin D deficiency than their healthy, age-matched peers.

Which led the researchers to a fascinating conclusion: Low vitamin D might be a risk factor for psychosis, and may actually trigger the initial episode in vulnerable people.

The link between mental health and other diseases

The U.K. researchers reported another amazing finding— patients with schizophrenia also often suffer from early-onset osteoporosis. And, of course, vitamin D is critical for bone health—the one role of the vitamin that the mainstream minions actually recognize.

Without a doubt, vitamin D is crucial for both the mind and the body. That’s why it’s critical to take 10,000 IU of D3 daily, especially at this time of year.

I recommend easy-to-take liquid forms combined with the potent marine carotenoid astaxanthin for added health benefits. (Simply visit, and type “astaxanthin” into the top right search bar to learn more about my personal formula recommendations.)

I also suggest aiming to get more D by working specific food sources into your diet. Foods rich in Vitamin D include:

• Beef liver and organ meats
• Egg yolks (preferably from farm fresh or cage-free eggs)
• Herring
• Organic mushrooms
• Oysters
• Sardines
• Shrimp
• Wild-caught Pacific salmon

So there you have it—an all-natural plan to support your mental health and prevent dementia and cognitive decline this winter and year-round.

I encourage you to educate yourself about all the other important ways vitamin D can boost your health.

Simply search my website archives—all of which are available to my newsletter subscribers.


1 “Seasonal plasticity of cognition and related biological measures in adults with and without Alzheimer disease: Analysis of multiple cohorts.” PLoS Med. 2018 Sep 4;15(9):e1002647.

2“Vitamin D deficiency in first episode psychosis: a case-control study.” Schizophr Res. 2013 Nov;150(2-3):533-7.