When Winter Affects More Than the Weather: Understanding Seasonal Affective Disorder

Written by Lauren Suraci, RN, Registered Psychotherapist (Qualifying)

As temperatures drop and daylight grows scarce, winter has a way of settling in, not just outside, but in our bodies and routines as well. With our northern landscape blanketed in snow and ice, the pace of life often turns inward. During this time, many people begin to notice subtle shifts in how they feel. Energy levels may be lower, motivation can wane, and social plans may suddenly seem less appealing. In fact, research suggests that most people experience some seasonal variation in mood and behaviour, rather than feeling emotionally the same year-round (Adamsson et al., 2018).

For many, these changes are temporary and manageable. These experiences are commonly referred to as the “winter blues.” While they can feel uncomfortable, they usually do not prevent people from carrying on with daily life, even if things feel a bit more effortful than usual (National Institute of Mental Health [NIMH], 2023).

When it is more than the winter blues

Seasonal Affective Disorder (SAD) is a form of depression that follows a seasonal pattern, most commonly emerging in the fall or winter months and easing as daylight returns in the spring or summer. While many people notice the mild seasonal changes described above, SAD involves symptoms that are more persistent and more disruptive to daily life (Melrose, 2015).

People experiencing SAD often find that their mood, energy, and motivation are significantly affected for weeks or months at a time. Tasks that once felt manageable may begin to feel overwhelming, and activities that typically bring enjoyment may no longer feel engaging. Unlike winter blues, which may come and go, SAD symptoms tend to continue across much of the season (Melrose, 2015). Understanding SAD as a seasonal form of depression can help individuals recognize when their experience goes beyond temporary seasonal discomfort and when additional support may be helpful.

Common symptoms of seasonal affective disorder

SAD can affect people differently. While not everyone will experience all of these symptoms, common experiences may include (NIMH, 2023):

• Mood
  A persistent low mood, feelings of heaviness, or a reduced sense of enjoyment or interest in activities that were previously meaningful.
• Energy and sleep
  Ongoing fatigue, low energy, or a sense of feeling slowed down, along with changes in sleep patterns, often sleeping more than usual.
• Thinking and concentration
  Difficulty concentrating, feeling mentally foggy, or experiencing a sense of hopelessness or discouragement about the future.
• Behaviour and daily functioning
  Withdrawing from social activities, reduced engagement in daily routines, or finding it harder to initiate or maintain activity.

Why Seasonal Affective Disorder happens

The exact cause of SAD is not fully understood. It is thought to develop through a combination of biological and environmental factors influenced by seasonal change. These shifts are not a personal failing; they reflect how sensitive the human nervous system is to variations in light, rhythm, and environment. Some commonly understood contributing factors include (Mayo Clinic, 2025):

Changes to the body’s internal clock (circadian rhythm)

• Reduced exposure to daylight during the fall and winter months can disrupt the body’s natural sleep–wake cycle. When this internal rhythm is thrown off, it can affect energy levels, mood, and overall emotional regulation.

Disruptions to sleep-related hormones

• Seasonal changes can also affect melatonin, a hormone involved in sleep patterns. Alterations in melatonin levels may contribute to changes in sleep, energy, and mood during the winter months.

Shifts in mood-related brain chemistry

• Sunlight plays a role in regulating serotonin, a brain chemical involved in mood and emotional balance. Lower light exposure may contribute to changes in serotonin activity, which can influence depressive symptoms in some individuals.

Reduced Vitamin D exposure

• During winter, people tend to spend less time outdoors, resulting in reduced exposure to sunlight on the skin. This can lead to lower Vitamin D levels. Vitamin D is believed to play a role in serotonin activity, and Vitamin D deficiency or insufficiency has been associated with clinically significant depressive symptoms.

Together, these factors help explain why some people experience a noticeable seasonal pattern to their mood and energy, particularly during periods of reduced daylight.

How psychotherapy can help

Psychotherapy can be a supportive way to navigate the emotional and behavioural challenges associated with Seasonal Affective Disorder. Therapy offers space to better understand how seasonal changes affect an individual, including their thoughts, routines, and emotional responses, and to develop strategies that feel manageable and sustainable.

Cognitive Behavioural Therapy (CBT) is one approach that has been shown to be particularly helpful for individuals experiencing SAD. When adapted for seasonal depression (often referred to as CBT-SAD), this approach focuses on identifying and gently challenging unhelpful thoughts related to the season, while also supporting changes in behaviour that can influence mood and energy. Therapeutic work may involve exploring discouraging beliefs about winter and increasing engagement in meaningful or enjoyable activities through behavioural activation, even when motivation feels low. This can help counter withdrawal and loss of interest that often accompany SAD (Rohan et al., 2015).

Importantly, psychotherapy is not about forcing positivity or eliminating seasonal discomfort. Instead, it aims to help individuals respond to seasonal changes with greater awareness, flexibility, and self-compassion, while maintaining engagement in daily life and valued activities.

References

Adamsson, M., Laike, T., & Morita, T. (2018). Seasonal Variation in Bright Daylight Exposure, Mood and Behavior among a Group of Office Workers in Sweden. Journal of Circadian Rhythms, 16(1), 2.

Mayo Clinic. (2025). Seasonal affective disorder (SAD). Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/seasonal-affective-disorder/symptoms-causes/syc-20364651

Melrose S. (2015). Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches. Depression research and treatment, 178564. https://doi.org/10.1155/2015/178564

National Institute of Mental Health. (2023). Seasonal affective disorder (NIH Publication No. 23-MH-8138) [Fact sheet]. U.S. Department of Health and Human Services. https://www.nimh.nih.gov/sites/default/files/documents/health/publications/seasonal-affective-disorder/seasonal-affective-disorder-508.pdfRohan, K. J., Mahon, J. N., Evans, M., Ho, S. Y., Meyerhoff, J., Postolache, T. T., & Vacek, P. M. (2015). Randomized Trial of Cognitive-Behavioral Therapy Versus Light Therapy for Seasonal Affective Disorder: Acute Outcomes. The American journal of psychiatry, 172(9), 862–869. https://doi.org/10.1176/appi.ajp.2015.14101293