Seasonal affective disorder is a type of depression triggered by changes in daylight during certain times of the year. For some, these shifts affect mood, concentration, productivity, decision-making, and the ability to function consistently at work and in daily responsibilities.
While many notice mild emotional changes during darker months, seasonal affective disorder involves a consistent pattern of symptoms that return each year and significantly affect wellbeing.
These symptoms are linked to the brain’s and body’s responses to light exposure, not solely to stress or lifestyle changes.
Understanding seasonal affective disorder and its symptoms can help individuals identify when seasonal changes affect their mental health and take practical steps to cope.
What Is Seasonal Affective Disorder?
Seasonal affective disorder is a recurring depression triggered by changes in daylight during specific times of the year. Depressive episodes occur in a particular season and resolve as the season changes.
For most individuals, symptoms typically begin in autumn or winter and improve in spring, although some experience symptoms during warmer months.
Unlike occasional low mood or the “winter blues,” SAD involves noticeable changes in mood, behaviour, and functioning. These changes follow the same seasonal pattern each year and usually last several months, around four to five months.
Research indicates that seasonal affective disorder is linked to disruptions in the body’s internal clock. Changes in daylight can alter serotonin and melatonin levels, affecting mood, sleep, appetite, motivation, and emotional stability.
To be diagnosed, symptoms must follow a consistent seasonal pattern for at least two consecutive years, with episodes occurring more often in certain seasons than others. This helps distinguish SAD from other types of depression or stress-related mood changes.
Symptoms of Seasonal Affective Disorder
Symptoms of seasonal affective disorder are similar to those of major depressive disorder, with additional features that vary by season.
These symptoms can range from mild to severe and may interfere with daily functioning, work, relationships, and wellbeing.
General Depressive Symptoms
Regardless of the season, seasonal affective disorder presents with core symptoms of depression. These include a persistent low, anxious, or empty mood that lasts most of the day, nearly every day, for at least two weeks.
Individuals may experience ongoing feelings of hopelessness, pessimism, guilt, worthlessness, or helplessness.
Other common symptoms include cognitive, emotional, and physical changes such as difficulty concentrating, remembering information, or making decisions. Many report a loss of interest or pleasure in activities they once enjoyed, along with increased irritability, frustration, or restlessness.
Physical symptoms may include changes in sleep, unexplained aches or pains, and unintentional weight changes.
In severe cases, individuals may have recurrent thoughts of death or suicide, which require immediate professional support.
Winter-Pattern Seasonal Affective Disorder
Winter-pattern SAD is the most common form. Symptoms usually start in late autumn or early winter and improve in spring as daylight increases. This pattern often resembles emotional and physical “hibernation.”
Common symptoms include excessive sleepiness or difficulty waking, increased appetite, especially for carbohydrates, and weight gain.
Many also experience social withdrawal, reduced motivation, and a desire to disengage from activities.
These symptoms are associated with increased melatonin production, reduced serotonin activity, and lower vitamin D levels during the darker months, all of which affect mood and energy.
Summer-Pattern Seasonal Affective Disorder
Although less common, some experience summer-pattern SAD, with symptoms emerging in spring or summer. This pattern is marked by heightened arousal and restlessness, rather than low energy and withdrawal.
Symptoms may include insomnia, reduced appetite and weight loss, increased anxiety or agitation, and heightened irritability. Some may also experience impulsive, aggressive, or intense emotional episodes, disrupted sleep cycles, and the stress associated with longer, hotter days.
Sleep disruption and heightened agitation during summer-pattern SAD can affect focus, emotional regulation, and workplace interactions, particularly in high-demand or fast-paced environments.
Differentiating SAD from Temporary Mood Changes
It is crucial to distinguish seasonal affective disorder from temporary mood changes caused by stress, holidays, workload, or lifestyle changes.
While short-term mood changes are common, SAD is defined by a consistent seasonal pattern and symptom severity that impacts daily functioning.
What Causes Seasonal Affective Disorder
Seasonal affective disorder develops when the body struggles to adapt to changes in daylight.
SAD results from the interaction between biological sensitivity and environmental exposure, rather than from external stressors or seasonal events alone.
Several factors contribute to the development of SAD:
- Reduced serotonin activity during periods of low light, affecting mood, motivation, and emotional regulation
- Vitamin D deficiency due to reduced sunlight, which may further impair serotonin function
- Altered melatonin regulation that disrupts sleep patterns and daily energy levels
- Circadian rhythm misalignment, where the body’s internal clock struggles to adjust to seasonal changes in daylight
Psychological responses to seasonal discomfort, such as dread of winter darkness or overstimulation in summer, may reinforce symptoms. These responses pertain to biological disruption rather than to the primary cause.
The interaction among light exposure, brain chemistry, and internal rhythms accounts for SAD’s consistent seasonal pattern and explains why early preventive strategies are effective.
Who Is More Vulnerable to Seasonal Affective Disorder?
Seasonal affective disorder affects people differently. While seasonal mood changes are common, certain biological, environmental, and personal factors increase the risk of developing SAD.
Recognising these risk factors can help individuals identify early signs, respond promptly, and reduce the impact of seasonal symptoms.
1. Demographic Factors
Specific demographic characteristics are linked to a higher risk of seasonal affective disorder.
SAD most often begins in young adulthood, though symptoms can appear at any age. Onset is less common in childhood and older age.
SAD is diagnosed more often in women than in men. The reasons are not fully understood, but hormonal, biological, and social factors may contribute to this difference.
2. Geographic Location and Latitude
Geographic location affects the risk of developing seasonal affective disorder. The condition is more common in regions with pronounced seasonal changes in daylight.
People living farther from the equator, especially at higher latitudes, have shorter daylight hours in winter. This increases the risk of disruptions to serotonin, melatonin, and circadian rhythms, which are central to SAD.
SAD rates are higher in northern regions, such as Alaska and New England, than in southern areas with more consistent daylight. Greater seasonal shifts in light exposure increase risk.
3. Existing Mental Health Conditions
People with specific mental health histories are more vulnerable to developing seasonal affective disorder as a co-occurring condition.
SAD is more common in people with mood disorders, especially major depressive disorder and bipolar disorder. It is particularly associated with bipolar II disorder, which involves recurrent depressive episodes and periods of hypomania.
It appears more frequently in people with anxiety disorders, panic disorder, attention-deficit/hyperactivity disorder (ADHD), and eating disorders. In these cases, seasonal changes may intensify existing symptoms or contribute to cyclical patterns of emotional distress.
4. Family History and Genetic Vulnerability
Genetic and family factors influence susceptibility to SAD. The condition sometimes runs in families, suggesting an inherited sensitivity to light.
Risk is higher for those with close relatives who have SAD or other severe mental health conditions, such as major depression or schizophrenia. Genetics alone does not determine outcomes but may increase sensitivity to environmental triggers, such as seasonal changes in daylight.
5. Individual Risk Factors in Context
Seasonal affective disorder rarely develops due to a single cause. Instead, vulnerability reflects the interaction between biological sensitivity, environmental exposure, mental health history, and personal circumstances.
Being aware of these factors can help individuals distinguish SAD from temporary seasonal low mood and support earlier, more effective coping strategies.
How to Cope With Seasonal Affective Disorder
Managing SAD requires a proactive approach. Since the condition follows a predictable pattern, early intervention is most effective. Common strategies include:
- Light therapy
Daily use of a bright light box helps compensate for reduced sunlight and supports the regulation of serotonin and melatonin, particularly in winter-pattern SAD. In addition to structured light therapy, increasing natural light exposure through regular outdoor activity can help regulate mood and circadian rhythm. - Psychotherapy
Cognitive behavioural therapy (CBT) for SAD helps people reframe unhelpful beliefs, reduce avoidance, and stay engaged in meaningful activities. Its benefits often extend beyond one season. - Medication
Antidepressants may help with moderate to severe symptoms, especially when started before the seasonal onset. Medication decisions should involve a qualified healthcare provider. - Vitamin D supplementation
Vitamin D may support mood regulation in winter-pattern SAD, but it is most effective as part of a broader support plan rather than alone.
Because SAD follows a predictable pattern, timing is critical for effective symptom management. Starting coping strategies before symptoms emerge can reduce their severity.
For winter-pattern SAD, this means beginning light therapy, psychotherapy, or medication in early autumn rather than waiting for mood changes.
A preventive approach allows the body and mind to adjust gradually, reducing the likelihood of severe disruption to mood, sleep, and daily functioning.
When Professional Support May Be Helpful
When seasonal affective symptoms impact mood, focus, work performance, or daily functioning, professional support can be valuable. Counselling provides a structured space to understand emotional patterns, strengthen coping strategies, and build resilience during seasonal transitions.
Support can also help differentiate between temporary seasonal low mood and ongoing mental health concerns that may need continued care.
Seasonal affective disorder highlights the strong link between emotional wellbeing and environmental or lifestyle factors. Recognising personal patterns, responding early, and prioritising self-care can help seasonal transitions feel more manageable and less disruptive.
D’Accord OAS provides counselling and wellbeing support for those experiencing emotional strain, stress, or mood changes related to life transitions and environmental factors. Services use a trauma-informed, person-centred approach to promote stability and resilience.
To learn more about available support options, visit the D’Accord OAS website or contact the team to discuss suitable services.
