What Causes Seasonal Depression?

Researchers have identified a myriad of possible causes for seasonal depression such as personality, gene, cultural variations, etc.

What Is Seasonal Depression?


Also called seasonal affective disorder (SAD), seasonal depression is a type of depression that happens in certain months of the year - most commonly in winter. Common symptoms include sleeping too much and having little to no energy, and overeating. The condition in the summer can include heightened anxiety.


Personality and Seasonal Depression


In a study comparing 43 SAD patients and 57 non-SAD patients, researchers tried to determine if there is a correlation between personal personality traits and seasonal depression; in other words, are people with certain personality characteristics more susceptible to seasonal depression?


Researchers used self-report surveys to measure and compare several dimensions of personality. The findings show that SAD patients and non-SAD patients have significant differences in regard to “openness.” SAD patients tend to be more imaginative, more emotionally sensitive and likely to entertain unconventional ideas than non-SAD patients.


Researchers suggest that this personality trait may explain why individuals with SAD are more sensitive to and may amplify the mild dysphoria typically associated with winter months.


Gene and Seasonal Depression


Some researchers say that seasonal depression has a genetic basis – people who carry certain genes are more likely to have symptoms.


In one such study, researchers enlisted 643 participants who consented to provide their medical records and to complete a survey questionnaire. Buccal mucosa samples were collected from each participant and genomic DNA was extracted.


The findings show that 5-HTR2A receptor gene plays a significant role in the phenomenon of seasonality in general, and in the development of winter-type SAD in particular. People with this gene are six times more likely to manifest winter or summer depression.


Culture and Seasonal Depression


Some researchers suggest that two dimensions of national culture, individualism/collectivism and power distance, cause different responses to the seasonal changes in ambient sunlight which, in turn, contributes to seasonal depression.


Individualism cultures (e.g., Australia, Britain, the U.S.) supports prioritizing self-interest above ingroup interests. In contrast, collectivistic cultures (e.g., China, Guatemala, Thailand) encourage prioritizing group interests above self-interest.


Power distance involves how people perceive power inequality. For instance, in high-PD countries (e.g., Malaysia, Philippines, Saudi Arabia), less powerful persons in hierarchical structures are likely to accept or even prefer inequality in power, value autocratic or paternalistic leadership styles, and describe authorities as feared and respected by their subordinates.


One researcher conducted a comprehensive, first-of-its-kind review of relevant studies of both winter and summer SAD, totaling 55 samples encompassing 18 countries and 38,408 participants, including 1931 with SAD.


And this researcher concluded that individualism and power distance are strongly related to seasonal depression. Specifically, winter depression correlated positively with individualism and negatively with power distance. In other words, winter depression is more prevalent in individualistic countries such as U.S. than in collectivistic countries such as China.

Sources consulted:

Joseph Kasof. 2009. “Cultural variation in seasonal depression: Cross-national differences in winter versus summer patterns of seasonal affective disorder.” Journal of Affective Disorders, 115: 79-86.

Eszter Molnar, et al. 2010. “Seasonality and winter-type seasonal depression are associated with the rs731779 polymorphism of the serotonin-2A receptor gene.” European Neuropsychopharmacology, 20: 655-662.

R. Michael Bagby, et al. 1996. “Seasonal and non-seasonal depression and the five-factor model of personality.” Journal of Affective Disorders, 38: 89-95.

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