The clocks fall back, the afternoons collapse into early darkness, and something shifts. For some, it’s a gentle settling, cozying inward for the colder months. For others, the shift feels heavier: a fog that descends and doesn’t lift, a weight that seems to grow as the days shrink. You might notice you’re sleeping more yet feeling less rested. The things that usually bring you pleasure—a favourite meal, time with friends, a project you care about—start to feel oddly flat. You wonder if you’re just being dramatic. You tell yourself to push through. You wait for the feeling to pass.
What you might be experiencing is Seasonal Affective Disorder, commonly known as SAD. It’s a form of depression that follows a seasonal pattern, most often emerging in late fall and persisting through winter. SAD is not simply “the winter blues,” that mild dip in mood many people notice when the weather turns cold. The winter blues might make you wish for a beach vacation. SAD makes getting out of bed feel like an act of will.
The causes of SAD trace back to biology. As daylight hours decrease, our bodies produce more melatonin, the hormone that signals sleep. At the same time, serotonin levels, which influence mood and well-being, tend to drop. This neurochemical shift can disrupt circadian rhythms, the internal clock that tells us when to wake and when to rest. The result is a body and mind out of sync with the demands of daily life that remain the same despite the season.
Certain factors can increase vulnerability. Living at higher latitudes, where winter days are shortest, raises the risk. Women are diagnosed more frequently than men, though this may reflect differences in help-seeking as much as biology. A family history of depression or SAD makes the condition more likely, as does having a personal history of depression or bipolar disorder. Young adults seem particularly susceptible, with symptoms often first appearing in the late teens or twenties.
The symptoms of SAD overlap with those of major depression, which is why it can be difficult to recognize. Persistent low mood is the hallmark, accompanied by a loss of interest in activities that once felt meaningful. Many people experience changes in appetite, particularly cravings for carbohydrates and sweets, and corresponding weight gain. Fatigue is common, even after a full night’s sleep. Social withdrawal that is uncharacteristic can be a sign. Difficulty concentrating is not simply a lack of discipline; it may be beyond your control.
A careful history helps distinguish SAD from other forms of depression that might happen to coincide with winter.
Various treatment approaches exist. Research supports the effectiveness of light therapy. A light box that delivers 10,000 lux of bright white light, used for 20 to 30 minutes each morning, can significantly improve symptoms within days to weeks. Timing is important: morning exposure helps reset the circadian rhythm, signalling to the body that the day has begun. Not all light boxes are created equal, so look for one specifically designed for SAD treatment, with UV-filtered light and the appropriate intensity.
Vitamin D supplementation is another avenue worth exploring with your medical or naturopathic doctor, particularly for those with documented deficiency. Our bodies synthesize vitamin D through sun exposure, and winter’s reduced sunlight can leave us lacking. The evidence on whether supplementation alone alleviates SAD symptoms is mixed, though it may offer benefit as part of a broader approach. A blood test can determine whether deficiency is a factor for you.
Beyond these interventions, psychotherapy offers substantial help. Cognitive behavioural therapy adapted for SAD addresses the thought patterns and behaviours that can deepen seasonal depression. Often, the most effective approach combines several strategies: light therapy in the morning, attention to sleep and exercise, and professional support to navigate the season.
It’s worth noting that a smaller subset of people experience the reverse pattern: depression that emerges in spring and summer and lifts in fall. Summer SAD tends to present differently, with insomnia, decreased appetite, weight loss, and agitation more prominent than the lethargy of winter SAD. The underlying mechanisms aren’t fully understood, though heat and longer days may play a role for some. If your mood consistently plummets when the temperatures rise, you may not be imagining it.
Recognizing SAD is the first step toward reclaiming the months you’ve been losing and reducing the sense of shame that may accompany your symptoms.
If you’ve been wondering whether what you’re experiencing is more than just the winter blues, I’d welcome the chance to explore that with you. Reaching out isn’t an admission that something is wrong. It’s an acknowledgment that you deserve to feel like yourself, regardless of the season.
