If your mood drops during the winter months, you may suffer from seasonal affective disorder (SAD). But exactly why some people are more susceptible to the winter blues than others has continued to stump researchers.
Now a new piece of the puzzle may be falling into place. Research suggests your personality type may play a big role in whether or not you fall prey to seasonal depression. Specifically, winter-time mood disorders are more common in those who score high on the personality traits of "openness" and "neuroticism."
If you suffer from SAD (a subtype of major depressive disorder), you already know the symptoms well: sluggishness, fatigue, irritability, depression, feelings of loneliness, anxiety and increased appetite/weight gain. (Incidentally, there's a rarer form of seasonal depression that occurs during the spring and summer months with its own set of symptoms, including insomnia and weight loss).
The more common form of seasonal blues — winter SAD — affects about 4% to 6% of the population, with another 10% to 20% experiencing a milder form. Women are more likely to experience SAD (four out of five sufferers are female), as are individuals prone to non-seasonal depression. Oddly enough, people with brown eyes have been shown to suffer more from SAD than those with blue or green eyes. The theory goes that blue-eyed people are more sensitive to light. Therefore, they don't need to absorb as much sunlight as brown-eyed people.
One of the major causes appears to be lack of sunlight during the fall and winter months. Shorter, darker days seem to dampen production of the mood-boosting brain chemical serotonin in SAD sufferers and elevate levels of melatonin, the sleep-inducing hormone produced at higher rates in the dark.
Sitting in front of a full-spectrum fluorescent light box for 30-plus minutes a day during the dark days of winter can help keep SAD at bay. (Photo: Lou Sander [CC BY-SA 4.0]/Wikimedia Commons)
However, because not everyone who experiences seasonal light deprivation undergoes a mood downturn, researchers have long suspected that individual characteristics, like personality, might also play a role.
To explore this link, several recent studies have examined the personalities of people with SAD using the five factor model of personality traits (FFM). This test scores individuals in five broad personality trait areas (also known as the "big five"): extraversion, agreeableness, conscientiousness, neuroticism and openness. Researchers believe that individual differences in these core personality traits account for why people react differently to similar situations.
In general, findings show a correlation between SAD and personality type, as well as stress coping style. Specifically, those with seasonal mood disorders tend to rate higher on openness and neuroticism than non-sufferers.
Diagram of the Big 5 personality traits that account for individual differences in how people react to similar situations. (Photo: U3081508 [CC BY-SA 4.0]/Wikimedia Commons)
Openness (also called "intellect") relates to having a broad array of interests, sensitivity to the environment around you, receptivity to new ideas and a preference for novelty over routine. Perhaps it's not surprising that those most attuned to the external world would be more emotionally affected by seasonal changes in weather and sunlight levels.
Neurotic individuals are more vulnerable to emotional instability and experiencing negative emotions, including anxiety, moodiness and irritation. Again, no surprise that pessimism and emotional imbalances would boost your chances of experiencing SAD (as well as non-seasonal depression).
Take a Five Factor personality test here to see how susceptible you may be to SAD.
Another personality trait that SAD-prone individuals share is an avoidance coping style when dealing with stress. That is, they get through the long, dark winter months using a form of hibernation (like excessive TV watching and sleeping).
Learn more about seasonal mood swings and effective treatments in this video.
Editor's note: This article has been updated with new information since it was originally published in October 2018.