Every November, you feel it starting. The low energy. The extra sleep. The creeping sense that everything is harder than it was a month ago.
Or maybe it's August for you. The heat, the disrupted sleep, the irritability.
Seasonal patterns in mental health are common, and often invisible until you track them.
How common are seasonal patterns?
About 5% of Americans meet criteria for seasonal affective disorder (SAD), the clinical diagnosis for seasonal depression. But many more people notice milder seasonal shifts that don't reach that threshold.
Symptoms typically start in October or November and lift in March or April. Some people feel it as early as August. Most don't feel fully back to normal until May.
The pattern reverses for about 10% of people with seasonal mood issues. Their symptoms appear in summer and lift in fall. This is sometimes called "reverse SAD" or summer-pattern depression.
Either way, the key feature is predictability. The same pattern, year after year, tied to the calendar.
Why seasons affect mood
Several mechanisms are at play:
Light exposure. Shorter days mean less sunlight, which affects serotonin production and circadian rhythm. Your internal clock gets misaligned with your schedule.
Melatonin changes. Darkness triggers melatonin production. In winter, your body produces more of it, which can increase sleepiness and fatigue.
Temperature and activity. Cold weather often means less outdoor time, less exercise, less social activity. These affect mood independently of light.
For summer patterns: Heat can disrupt sleep, cause physical discomfort, and increase irritability. Longer days can also throw off circadian rhythms in the opposite direction.
What seasonal depression looks like
Winter-pattern symptoms:
- Sleeping more than usual
- Low energy despite extra sleep
- Increased appetite, especially for carbs
- Weight gain
- Social withdrawal
- Difficulty concentrating
- Feeling sad or hopeless
Summer-pattern symptoms:
- Trouble sleeping (insomnia)
- Decreased appetite
- Weight loss
- Anxiety and agitation
- Restlessness
The symptoms are almost opposite. Winter SAD tends toward oversleeping and overeating. Summer SAD tends toward insomnia and appetite loss.
How to identify your pattern
You need at least two years of data to confirm a seasonal pattern. One bad winter could be coincidence. Two bad winters in a row, with good summers between them, suggests a pattern.
Here's how to track it:
Monthly assessments. Take the PHQ-9 or DASS-21 on the same day each month. First of the month, last Sunday, whatever works. Just be consistent.
Record the basics. Date, score, and any major life events. You want to separate "bad month because of work stress" from "bad month because it's February."
Look for patterns after 12+ months. Do your scores rise in the same months? Do they drop in the same months? A 5+ point swing that correlates with season is worth paying attention to.
Note the timing. When exactly do symptoms start? When do they lift? This information helps you plan prevention.
What the data might show
Clear seasonal pattern: Scores spike November-February, drop March-October (or the reverse for summer). This predictability is useful because you can prepare.
Stress-layered pattern: Scores are generally higher in winter, but big spikes correlate with specific stressors. The season makes you vulnerable; life events push you over the threshold.
No pattern: Scores fluctuate, but not tied to season. Your mood changes have other causes.
Gradual shift over years: Winter scores are getting worse each year, or the low period is getting longer. This suggests worsening that may need intervention.
Using the pattern
Once you know your pattern, you can work with it instead of being blindsided by it.
Prepare in advance. If symptoms typically start in November, begin preventive measures in October. Light therapy, exercise routines, social commitments: set them up before you need them.
Adjust expectations. January might not be the month for ambitious new projects. Knowing this lets you plan accordingly rather than beating yourself up for low productivity.
Talk to your doctor. Some people start or adjust medication seasonally. Others begin light therapy before symptoms hit. Your pattern data helps make these conversations concrete.
Watch for early warning signs. If symptoms usually start mid-October, a rising score in early October is a signal to act. Early intervention works better than waiting until you're deep in it.
Light therapy
For winter-pattern seasonal depression, light therapy is often the first recommendation. Exposure to bright light (10,000 lux) for 20-30 minutes each morning can help reset circadian rhythm and boost serotonin.
Key points:
- Morning exposure works better than evening
- Consistency matters more than duration
- Effects typically appear within 1-2 weeks
- Some people need it all winter; others just during the worst months
Light therapy is less useful for summer-pattern depression, which may benefit more from reduced light exposure, cool environments, and careful management of sleep schedules.
When to seek help
Tracking is useful, but it's not treatment. Consider professional help if:
- Scores reach moderate or severe range (10+ on PHQ-9)
- Symptoms significantly interfere with work or relationships
- Pattern is getting worse year over year
- You're having thoughts of self-harm
- Self-management strategies aren't enough
A mental health provider can offer more structured treatment: medication, cognitive behavioral therapy for seasonal depression (CBT-SAD), or combined approaches.
The value of the record
After a few years of tracking, you'll have something useful: evidence.
Not "I think winters are hard for me" but "my PHQ-9 averages 12 in January and 4 in July, with symptoms starting mid-October for the past three years."
This kind of data changes conversations with doctors from vague complaints to specific patterns. It helps you distinguish seasonal effects from other life factors. And it gives you the ability to predict and prepare rather than react.
Seasonal patterns aren't random. They're predictable. And predictable means manageable, if you're paying attention.
Getting started
1. Pick a monthly date. First Sunday, last day of the month, whatever you'll remember.
2. Take the same assessment. PHQ-9 is standard for depression. DASS-21 covers anxiety and stress too.
3. Record it somewhere you won't lose. Spreadsheet, notes app, paper calendar. Include the date, score, and brief context.
4. Review after 12 months. Look for patterns. Are certain months consistently higher? Lower?
5. Keep going. The pattern gets clearer with more data. Two years is better than one. Three is better than two.
You can't change the seasons. But you can learn how they affect you and use that knowledge to protect your mental health year-round.
Track your patterns with Survey Doctor
Set up a monthly reminder to take the PHQ-9 or DASS-21 and build a record of your seasonal patterns over time. Survey Doctor saves your history so you can spot trends across months and years. Start tracking now.