Why You Feel Down Every Winter - Seasonal Depression (SAD) and How to Fight It

What Is Seasonal Affective Disorder (SAD)?

Seasonal Affective Disorder (SAD) is a type of depression that recurs during specific seasons. The most common form is the autumn-winter type, with symptoms appearing around October to November as daylight hours shorten, then naturally improving in spring. In Nordic countries, roughly 10% of the population is estimated to experience SAD, and in Japan the prevalence tends to be higher in regions at higher latitudes.

SAD is not simply "feeling a bit low in winter." In the DSM-5, it is classified as Major Depressive Disorder with a seasonal pattern specifier - a legitimate mental health condition. It is often dismissed as laziness or lack of willpower, but it is a biological phenomenon driven by shifts in neurotransmitters and hormonal balance in the brain, not something that can be easily overcome through sheer determination.

Symptoms of SAD

Typical symptoms include persistent low mood, loss of interest or pleasure, hypersomnia (feeling sleepy no matter how much you sleep), overeating (especially carbohydrate cravings), weight gain, difficulty concentrating, and social withdrawal. While typical depression often involves insomnia and appetite loss, SAD is characterized by hypersomnia and overeating.

Often-overlooked symptoms include a heavy, leaden feeling in the body, heightened sensitivity to minor irritations, and excessive rejection sensitivity in relationships (an exaggerated fear of being turned down). These are easily mistaken for personality traits, leaving many people unaware they have SAD and simply enduring each winter in silence.

Common Misconceptions

"It's the Cold That Makes You Feel Down" Is Inaccurate

The cause of SAD is not cold temperatures but lack of light. Even in warm equatorial regions, SAD-like symptoms have been reported during prolonged rainy seasons that block sunlight. Conversely, in cold but sunny regions, prevalence tends to be somewhat lower. The decisive factor is the amount of light reaching the eyes, not the temperature.

"It Happens Every Year, So There's Nothing I Can Do" Is Wrong

Because SAD follows a repeating pattern, it is uniquely suited to preemptive intervention. Rather than reacting after symptoms appear, starting light therapy or exercise habits two to four weeks before daylight begins to reduce can potentially prevent onset altogether.

The Mechanisms Behind SAD

Daylight and Serotonin

Sunlight promotes the production of serotonin, a neurotransmitter that stabilizes mood. When daylight hours decrease in winter, serotonin production drops, leading to low mood. Serotonin, sometimes called the "happiness hormone," is involved not only in mood stability but also in appetite and impulse control. Winter carbohydrate cravings are thought to be a compensatory behavior as the brain attempts to increase uptake of tryptophan, the precursor to serotonin.

Excess Melatonin Secretion

Dark environments increase the secretion of melatonin (the sleep hormone). The long winter nights trigger excess melatonin production, causing hypersomnia and fatigue. In healthy individuals, morning light exposure promptly suppresses melatonin secretion, but in people with SAD this suppression response is blunted, allowing melatonin to persist during daytime hours.

Disrupted Body Clock

Changes in daylight hours disrupt the circadian rhythm (body clock), affecting sleep-wake cycles, hormone secretion, and body temperature regulation. In winter, the late sunrise makes "phase delay" more likely, where the internal clock shifts later. When the body is still in "night mode" at wake-up time, morning performance drops dramatically. Books on seasonal mental health can help you learn more.

Coping Strategies

1. Light Therapy

The first-line treatment for SAD is light therapy. A 10,000-lux bright light therapy device is used for 30 minutes after waking in the morning. It is effective for roughly 60-80% of patients, with improvement typically seen within one to two weeks. Light therapy devices are commercially available as medical devices and can be used at home. The key is using it in the morning. Exposure to strong light in the evening or at night can further delay the body clock, potentially worsening symptoms. There is no need to stare directly at the light source; keeping it at an angle where it enters peripheral vision while reading or eating breakfast is sufficient.

2. Morning Sunlight Exposure

Even without a light therapy device, exposure to natural morning light can be beneficial. Go outside within 30 minutes of waking and spend 15-30 minutes in sunlight. Even on cloudy days, outdoor light levels are more than 10 times greater than indoors, so it still helps. Light through windows is less effective because glass blocks UV rays, so getting outdoors is recommended whenever possible. Building it into daily routines, such as walking one extra train stop during your commute, is the key to consistency.

3. Exercise

Aerobic exercise promotes the release of serotonin and endorphins, alleviating SAD symptoms. Moderate-intensity exercise (walking, jogging, swimming) for about 30 minutes, three to five times a week, is recommended. Exercising outdoors is especially effective because it combines the benefits of sunlight exposure and physical activity. Exercise plays a major role in maintaining mental health, and is worth prioritizing at a level of "even if I don't have time for medication, I will make time to walk."

4. Medication

For severe symptoms, SSRIs (selective serotonin reuptake inhibitors) may be prescribed. Bupropion is the only medication FDA-approved for preventive use in SAD. It is typically started before symptoms appear in autumn and discontinued in spring. Books on mental health are also a useful reference.

5. Environmental Adjustments and Lifestyle Habits

Setting room lighting brighter, switching from blackout curtains to thinner ones to let morning light in, eating lunch near windows or outdoors: small daily adjustments accumulate into meaningful effects. Vitamin D supplementation is also worth considering. Vitamin D, synthesized in the skin through sunlight, tends to be deficient in winter, and supplementation has been suggested to contribute to mood improvement.

How SAD Differs from Typical Depression, and When to Seek Help

The biggest difference between SAD and typical depression is the presence of a seasonal pattern. If symptoms appear in the same season for two or more consecutive years and resolve in spring, SAD is likely. As a self-check, if "overeating," "oversleeping," and "body feels like lead" all occur together in autumn and winter, consider consulting a mental health professional. Allowing your circadian rhythm (body clock) to remain disrupted extends recovery time, making early intervention key.

Summary

Feeling down in winter is not "just in your head" - it is a physiological response to reduced daylight. Light therapy, morning sunlight exposure, exercise, environmental adjustments, and medication when needed. Knowing these coping strategies gives you the strength to get through each winter. SAD's greatest advantage is its predictability. Because the pattern repeats each year, proactive measures are possible. Before this autumn arrives, try one approach that suits you.