Fishing for happiness: Omega-3 and seasonal affective disorder

As the days get shorter and the weather colder, keeping that frown upside down becomes an arduous task. While you might think you have what it takes to bear the elements through sheer willpower, your genetics and neurochemistry disagree. 

Studies of seasonal affective disorder (SAD) in Iceland and in various regions globally show that genetics and a diet that nourishes the brain play a vital role in combating SAD as well as other life-altering mood disorders like anxiety and depression.

Seasonal affective disorder is a medically-recognized mental illness with a set criteria to diagnose. Treatment comes in the same forms as other mental illnesses — psychotherapy, medication, lifestyle changes, and light therapy — and symptoms of SAD include lethargy, appetite changes, and a variety of depressive symptoms. SAD can occur during any season, but the majority of people with SAD demonstrate the onset of these changes during the fall and winter, with symptom remission in the spring on a recurring basis.

“The Iceland and Japan cases refute the latitude hypothesis and highlight the importance of analyzing other factors, including diet and genetics, that can contribute to mood disorders like SAD.”

For decades, scientists believed the dominating factor causing SAD was the amount of light people were exposed to: that clock genes, responsible for much of our circadian rhythm, made people sensitive to light conditions that fluctuate with seasonality and latitude. Studies in the U.S. revealed that SAD was significantly higher in winter months at higher latitudes, providing evidence of the link to light exposure.

Nevertheless, more recent studies of Icelandic and Japanese populations have complicated the picture. One famous example comes from a study that found, despite Iceland’s closer proximity to the Arctic and shorter days, it had significantly lower rates of SAD compared to the U.S. Additionally, seasonality demonstrated little to no impact on SAD in Iceland when comparing summer and winter rates. It turns out it isn’t only the geographic latitude of the nation itself that’s responsible for this result; genetics matter as well. Numerous studies have measured a lower prevalence of SAD in Icelandic descendants who recently immigrated to Canada than in the Canadian population.

Another study dating back to the late 1990s by Joseph Hibbeln dove deeper into the role of diet and discovered a negative relationship between fish consumption and levels of mood disorders. So not only does the Icelandic population have a genetic boost against SAD — they’ve developed a dietary one, too. While the average person’s fish consumption in other countries is around 50 to 70 pounds per year, it’s 225 pounds in Iceland. Japan has a similarly high rate of seafood consumption and has also displayed low rates of SAD.

“It turns out it isn’t only the geographic latitude of the nation itself that’s responsible for this result; genetics matter as well.”

To further analyze the correlation between fish consumption and mood, scientists looked into the relationship of omega-3 fatty acids, a key nutrient in fish. Omega-3 fatty acids are unsaturated fats most commonly found in marine life. As the Western world becomes more developed, fewer omega-3 unsaturated fats have been incorporated into its foods. Individuals with depressive disorders indicate omega-3 deficits in biological markers, while omega-3 supplementation was correlated with improved mood.

The Iceland and Japan cases refute the latitude hypothesis and highlight the importance of analyzing other factors, including diet and genetics, that can contribute to mood disorders like SAD. Although eating more fish and nuts high in omega-3 fatty acid concentrations can help, it is certainly not the only approach. More research needs to be conducted into the benefits and risks of increased omega-3 intake before it could be used as a treatment for SAD. As anxiety, depression, and SAD become more prominent, the potential of omega-3 looms large.