As the days grow shorter and temperatures drop during the autumn months, many individuals experience more than just the familiar routine of pulling out their cozy woolly jumpers and activating the central heating. For some, the transition into autumn signals the onset of Seasonal Affective Disorder (SAD), a type of depression that surfaces in alignment with the changing seasons. This condition can bring about feelings of heaviness and sadness, particularly as the evenings close in and mornings become increasingly dreary.
Although Seasonal Affective Disorder was formally recognized by mental health professionals only in the 1980s, the connection between seasonal changes and human mood has been noted for centuries. The "Yellow Emperor’s Classic of Medicine," a Chinese text dating back to approximately 300 BC, noted the correlation between the seasons and the well-being of living organisms. This ancient text proposed that during winter, individuals should “retire early and get up with the sunrise,” promoting a lifestyle that encourages quieter desires and subdued mental activity.
In modern times, researchers have been uncovering the intricate links between our biology and the changing seasons. Dr. Cathy Wyse, a chancellor’s research fellow at the University of Edinburgh, emphasizes that significant advancements have been made in understanding that seasonal fluctuations in human mood are likely rooted in our physiology. Large-scale research initiatives, such as the UK Biobank, have enabled scientists to observe these seasonal patterns in mood across hundreds of thousands of participants over extended periods, which was previously unattainable.
Determining where to draw the line between typical winter sluggishness and clinical depression can be challenging. SAD is classified as a subtype of major depression or bipolar disorder, characterized by a predictable seasonal pattern: symptoms typically emerge in autumn or winter and subside in spring. Along with the hallmark signs of depression, individuals may experience longer sleep durations, increased lethargy, and heightened cravings for carbohydrates. The triggers behind these changes are still under investigation but are believed to be closely linked to decreased daylight.
Light plays a critical role in regulating our internal body clock, also known as the circadian rhythm, which in turn influences hormone release, alertness, and mood. Insufficient exposure to natural light—especially when combined with excessive artificial light during the evening—can lead to a disconnection between our biological rhythms and the external environment. Some individuals may exhibit heightened sensitivity to these shifts, making them more vulnerable to mood changes.
Dr. Wyse and her colleagues are actively investigating the seasonal effects in individuals with bipolar disorder, noting that manic episodes often peak in spring, while depressive episodes tend to be more prevalent during the darker months. “We suspect that individuals with bipolar disorder may be particularly sensitive to light and seasonal cues, triggering their symptoms,” Dr. Wyse explains.
Even those without a clinical diagnosis of depression can experience a milder form of seasonal mood decline known as subsyndromal SAD or “the winter blues.” In the UK, approximately one in five individuals are affected by this condition, although only about 2% meet the criteria for full-fledged SAD. Beyond mood, research indicates that seasonal biology influences a range of physical factors, including fluctuations in the expression of over 4,000 protein-coding genes in white blood cells and fat, as well as variations in blood cellular composition throughout the year.
Dr. Wyse and her team recently analyzed four years of sleep data from half a million participants in the UK Biobank. Their findings indicate that during the winter months, people not only sleep longer but also report poorer sleep quality compared to the summer. These findings will be presented at the British Sleep Society conference in Brighton next week, highlighting the need for increased awareness of the impact of seasonal changes on sleep patterns.
Despite the natural occurrence of these seasonal changes, societal expectations often demand that individuals maintain their usual routines, making it difficult to cope. While hibernation might seem appealing, it's not a viable option. The most effective remedy for combating the winter slump is light. Bright light therapy remains the gold standard for treating SAD, although the timing and dosage are crucial for its effectiveness. For those unable to commit to daily sessions in front of a light box, natural sunlight serves as a powerful alternative.
Studies conducted on Amish communities in the United States, who spend more time outdoors and less time subjected to bright artificial light at night, reveal some of the lowest rates of SAD recorded among Caucasian populations. In contrast, New York City reports a prevalence of approximately 4.7%. Early exposure to bright, natural light helps synchronize the circadian clock and suppress the production of melatonin, a hormone that can induce grogginess. Additionally, light has a direct alerting effect; research has shown that an hour of blue-enriched light can enhance reaction times more effectively than consuming two cups of coffee.
While light exposure is essential, it is not the sole solution for managing SAD. Cognitive Behavioral Therapy (CBT) designed specifically for SAD can be equally effective as light therapy, enabling individuals to reframe their perceptions of winter rather than merely managing symptoms. As winter approaches, it is crucial to recognize that the season will come regardless; by altering our mindset, we can reclaim joy during the darker months.
To effectively combat the winter blues and enhance overall well-being, consider incorporating light therapy, spending time outdoors, and exploring cognitive behavioral approaches. By taking proactive steps, individuals can better navigate the seasonal transitions and emerge with a more positive outlook.
