Issue 037

Why do my symptoms come back in the same month every year?

Yvette Rose · 7 min read

Symptoms come back in the same month because your body keeps a calendar. Light, temperature, pollen and memory all change on a yearly schedule, and your mood, sleep, headaches and even your lab numbers move with them. Once you can name the month, you can usually name what is driving it, and that gives you something to plan around and something concrete to bring to your doctor.

Light sets the first calendar

The clearest example is seasonal affective disorder. The National Institute of Mental Health describes the winter pattern as starting in late fall or early winter, lifting in spring and summer, and lasting about 4 to 5 months of the year. A diagnosis requires the pattern to show up for at least two years in a row, which is exactly the "same month every year" experience. A summer pattern exists too and is less common.

Seasonal depression is diagnosed much more often in women, more often the farther north you live, and it usually begins in young adulthood. A 24 year old who falls apart every November belongs in this conversation as much as a woman in perimenopause or a man in his fifties who goes quiet every January.

Sleep shifts with the light as well. In a study of 188 sleep clinic patients, people got about 30 minutes more REM sleep in winter than in spring. The clock change has its own record. The American Academy of Sleep Medicine links the spring switch to daylight saving time with a higher risk of heart attack and stroke and a rise in fatal car crashes.

Your lab numbers have seasons too

Most people never hear this part. Vitamin D peaks in late summer and bottoms out in late winter. In a US analysis of 3.44 million blood samples, the high point was August and the low point was February.

The thyroid signal, TSH, generally runs highest in winter. In a large Korean group, people with a borderline high TSH were more likely to return to normal when the follow up test fell in summer or fall.

Your cholesterol moves too. In one US study, 22 percent more people crossed the 240 line for total cholesterol in winter than in summer. Blood pressure runs higher in the cold, by about 6 points on the top number and three on the bottom for readings taken at home. In more than 285,000 US veterans with diabetes, A1c ran about 0.2 higher in winter than in summer.

Testosterone is the one where the studies disagree. Two large US datasets found no seasonal pattern at all, so I would not read the calendar into that number.

Think about what this means for a man in his fifties who books his physical every January. He may be seeing his cholesterol and blood pressure at their highest point of the year. A borderline result deserves a repeat in a different season before anyone calls it a trend.

Name the month and you can usually name what is driving it.

Pollen, headaches and the dates your body remembers

Allergy season is longer than it used to be. Across 60 North American stations from 1990 to 2018, pollen seasons grew by 20 days and pollen counts rose 21 percent. Hay fever brings more than sneezing. Mayo Clinic lists extreme tiredness and poor sleep among its effects, with tree pollen arriving in early spring, grass in late spring and summer, and ragweed in fall. If you are exhausted every April, pollen belongs on your list.

Few conditions follow the calendar as closely as cluster headache. The attacks often appear seasonally, usually in spring and fall, they are more common in men, and they typically begin between ages 20 and 40. The National Institute of Neurological Disorders and Stroke notes that they can be mistaken for allergies.

Memory keeps dates as well. The VA's National Center for PTSD describes anniversary reactions. Around the date of a loss or a trauma, people sleep badly, lose focus and can have physical symptoms such as fatigue and pain, and most feel better within one to two weeks. I ask every client what else happened in the month that keeps going wrong. Sometimes a death, a divorce or a diagnosis is sitting right there in it.

The winter holidays stack several of these drivers at once. The American Heart Association reports that more people die of heart attacks between December 25 and January 1 than at any other time of year. Holiday weight gain is real, though small. In a study of 195 adults, the average gain from Thanksgiving to New Year was under one pound, and it was not lost over the rest of the year.

What I would do first

I would get out a 12 month calendar and mark every month the symptom showed up over the last two or three years. Old texts, photos, pharmacy records and sick days all help you reconstruct it. Headache doctors ask patients to keep a journal for this exact reason: it helps them diagnose the type of headache and find the right treatment.

Next I would match the month to a driver. The usual candidates are light, cold, pollen, the school or work calendar, and a date with history.

For the dark months, I would get outside in the morning. If you are considering a light box, the dose used for winter depression is 10,000 lux for about 30 to 45 minutes, first thing in the morning. Talk to your doctor before using one if you have bipolar disorder, an eye condition such as glaucoma or cataracts, or a prescription that makes you sensitive to light.

On vitamin D, the recommended intake for adults up to age 70 is 600 IU a day, rising to 800 IU after 70, and the upper limit for adults is 4,000 IU a day. The Endocrine Society's 2024 guideline suggests against routine vitamin D testing in healthy adults, and against taking more than the recommended intake before age 75. Check with your doctor first if you have kidney disease, take prescriptions, or are pregnant or nursing.

I do not diagnose, order tests or treat. My part is helping you see the pattern clearly enough that your doctor can act on it.

When to push harder with your doctor

Bring the calendar with you. Push when low mood has arrived in the same season two years running, and ask directly about a seasonal pattern. If low mood ever comes with thoughts of harming yourself, call or text 988 in the US right away.

Push when a borderline thyroid, cholesterol or blood pressure result is about to become a prescription on the strength of a single winter reading. Ask whether a repeat test in another season makes sense first.

Push when a severe headache keeps the same appointment every year, and ask about cluster headache by name.

Chest pain, chest pressure or shortness of breath gets the same response in December as in any other month. Call 911, and never wait for a holiday to be over.

FAQ

Is seasonal depression real or is it the winter blues?

It is real. The National Institute of Mental Health classifies seasonal affective disorder as a type of depression with a seasonal pattern, lasting about 4 to 5 months of the year. A diagnosis requires the pattern to appear for at least two years in a row.

Can blood test results change with the season?

Yes. Vitamin D runs lowest in late winter, TSH and cholesterol generally run higher in winter, and blood pressure rises in the cold. A borderline result is worth repeating in a different season before you treat it as a trend.

Should I have my vitamin D tested every winter?

Probably not if you are healthy. The Endocrine Society's 2024 guideline suggests against routine vitamin D testing in healthy adults. The recommended intake is 600 IU a day up to age 70, and anyone with kidney disease, prescriptions, or a pregnancy should ask their doctor before supplementing.

Why do I get headaches at the same time every year?

Two common reasons are allergies and cluster headache. Cluster headaches often appear seasonally, usually in spring and fall, and can be mistaken for allergies. Keep a headache journal with dates and bring it to your doctor.

What is an anniversary reaction?

It is a rise in distress around the date of a loss or a trauma. People often sleep badly, lose focus and can have physical symptoms such as fatigue and pain, and most feel better within one to two weeks. If it lasts longer or gets in the way of your life, ask for support.

In good health,
Yvette Rose

Sources

This is general wellness education and not medical advice, diagnosis or treatment. Talk to a qualified professional, especially if you are pregnant, nursing, taking medication or managing a condition.

It all starts in the gut.