TLDR: Seasonal Affective Disorder (SAD) is a recognised form of depression that follows a seasonal pattern, most commonly worsening through autumn and winter. Below, Ryan Hegarty, BABCP-accredited CBT therapist at Slán Therapy, breaks down the symptoms, what causes it, and the treatment options that actually help.
As the days shorten and the light fades, plenty of people notice a shift in mood and energy. Some of this is the ordinary “winter blues.” For others, it’s something more persistent: Seasonal Affective Disorder (SAD), a recognised, diagnosable form of depression that follows a seasonal pattern. This guide covers what SAD actually is, the symptoms to look out for, what’s believed to cause it, and what can help.
What is Seasonal Affective Disorder?
Seasonal Affective Disorder is a type of recurring depression that becomes more pronounced during a specific time of year, most commonly affecting mood and energy levels. It tends to be more common in younger people, women, and those living further from the equator, where seasonal light changes are more extreme. Most people experience it starting in autumn and continuing through winter, though a smaller number experience the reverse pattern, starting in spring and lifting by summer.
SAD isn’t just low motivation on a grey day. In the UK, an estimated one in five people experience the milder “winter blues,” while around 2% meet the criteria for the diagnosable condition, Seasonal Affective Disorder.
Symptoms of Seasonal Affective Disorder
SAD affects people differently, so any list is necessarily a simplification. Broadly, the changes tend to fall into three categories: physical, cognitive, and emotional or behavioural.
Physical changes
- Energy: reduced activity levels, and everyday tasks feeling harder to keep up with due to persistent tiredness
- Appetite: increased cravings, particularly for carbohydrates (in summer-pattern SAD, this often reverses to reduced appetite)
- Weight: gain or loss, depending on how appetite is affected
- Sleep: oversleeping and unrefreshing sleep are common in winter-pattern SAD; summer-pattern SAD can involve the opposite, including insomnia
- Digestion: stomach or gastrointestinal discomfort
- General aches: headaches, muscle aches, and a broader sense of feeling run down without an obvious cause
Changes in thinking
- Brain fog: slower thinking, and difficulty concentrating or focusing
- Indecisiveness: decisions feeling harder to make or commit to
- Self-criticism: a heavier, more frequent inner critic, with thoughts of not being good enough
- Thoughts of death: more frequent thoughts about death, or not wanting to be alive. If this applies to you, it’s worth taking seriously and speaking to someone as soon as possible
Changes in how we feel and behave
- Mood: feeling low, tearful, or persistently down
- Interest: things that usually bring enjoyment, work, hobbies, socialising, start to feel flat or like a burden
- Inadequacy: feeling more useless, unlikeable, or worthless than usual
- Detachment: a sense of distance from other people or the world generally
- Numbness: difficulty feeling much at all
- Irritability: a shorter fuse, snapping more easily at others or yourself
- Confidence: more self-doubt than usual
- Self-care: letting personal care slip, showering or grooming less, eating less well
- Motivation: everyday responsibilities, work, bills, laundry, becoming harder to keep on top of
- Socialising: withdrawing from friends and family
- Substance use: increased use of alcohol or drugs
For SAD to be considered as a diagnosis rather than a difficult stretch, these changes typically need to ease or lift for at least two months when the season changes.
What causes Seasonal Affective Disorder?
There’s no single confirmed cause of SAD, in line with most mental health conditions, but several factors are understood to increase the likelihood of developing it:
- Location: living further from the equator increases risk, as these regions see more extreme seasonal light changes
- Circadian rhythm: your body’s internal clock, governing sleep and waking, can struggle to adjust to shorter winter daylight hours
- Vitamin D: reduced sunlight exposure in winter, from wearing more layers and spending more time indoors, can lower vitamin D levels, which plays a role in serotonin activity and mood regulation
- Melatonin: this hormone, which influences sleepiness, increases as daylight hours shorten, contributing to that heavier, more lethargic feeling in winter
How do we manage Seasonal Affective Disorder?
There are several effective approaches to managing SAD, and most people find a combination works best.
Self-help
Small, consistent changes can meaningfully shift symptoms: regular exercise, time outdoors during daylight hours, and a consistent sleep schedule all support mood regulation. Feeling low and unmotivated rarely happens in isolation, so talking to people close to you about how you’re feeling and letting them understand what’s going on can make a genuine difference to how supported you feel through it.
Light therapy
Given the clear link between reduced light and SAD symptoms, light therapy works by replicating natural daylight through a bright artificial light box. Evidence suggests around 30 minutes of use each morning can meaningfully reduce symptoms. Dawn-simulation alarm clocks, which gradually brighten rather than switching on abruptly, can also help with the difficulty of winter mornings.
Cognitive Behavioural Therapy
CBT has a strong evidence base for a wide range of mental health conditions, including SAD. It works by helping identify the thinking and behavioural patterns that maintain symptoms, and building practical ways to shift them. Rather than waiting out the season, CBT gives you a structured way to work through what’s actually keeping the low mood going.
Medication
Antidepressants can be an effective option for some people with SAD. This isn’t something I prescribe or advise on directly; it’s a conversation to have with your GP, who can talk through whether medication might be a helpful part of your treatment plan.
Is it time to speak to someone?
Seasonal Affective Disorder affects a significant number of people across the UK every year, and if your mood and energy shift noticeably with the seasons, you’re not dealing with something unusual or something to simply push through. There are effective, evidence-based treatments available, and getting the right support earlier tends to make a real difference.
If SAD is affecting you and you’d like to talk about whether CBT could help, book a free discovery call and we’ll take it from there.
