Autumn Fatigue: What It Is and What Science Says About Feeling Tired in the Fall

“Astenia otoñal,” autumn fatigue, is a phrase that turns up every September in the Spanish press, in pharmacies and in everyday conversation. It describes something many people recognize: getting up, concentrating and feeling motivated all take more effort. What usually goes unsaid is that it isn’t a diagnosis, and that research on seasonality offers a more interesting explanation than the “five keys to beating it” formula.

A popular label, not a clinical entity

The word asthenia means weakness or lack of strength, and in medicine it’s used as a symptom, not a disease. “Autumn fatigue” or “spring fatigue” are popular labels: they don’t appear in the DSM-5 or the ICD-11, and there are hardly any studies that measure them under that name.

What does exist in the scientific literature is a broader concept, seasonality: the tendency of many people to vary their sleep, energy, appetite and mood over the course of the year. Studies by Kasper, Wehr, Rosenthal and colleagues (1989) in the general population of Maryland showed that these changes form a continuum: at one end, people who barely notice them; in the middle, mild discomfort; at the other end, seasonal affective disorder.

What Spain calls autumn fatigue would correspond to the mild zone of that continuum, what the English-language literature sometimes calls the winter blues or, when more pronounced, subsyndromal seasonality.

Why autumn and not winter

If the cause were simply a lack of light, the worst point would be December. The review by Zhang and Volkow (2023) in Translational Psychiatry suggests looking at another variable: the speed at which day length changes, which peaks around the equinox in late September. The article on why the end of summer hits harder than winter develops this idea in detail.

The underlying mechanism is the circadian clock, which syncs itself to light every day. Its sensitivity depends on the time: early-morning light tends to shift it earlier and evening light to push it later (Khalsa et al., 2003). In autumn the sun rises later and we spend more time indoors, so the clock gets less of the signal that keeps it on time. For people with an evening chronotype, who already tend to run behind the social schedule, that mismatch is more noticeable.

What irregular sleep adds

Sleep regularity matters as much as sleep duration. In the study by Phillips et al. (2017), which followed 61 university students for a month, those with more irregular schedules showed a much later melatonin rhythm than those with regular schedules, despite sleeping similar amounts on average, and they also had less contrast between daytime and nighttime light exposure.

It’s a small, correlational study, but it illustrates the mechanism: the return from summer vacation, with its abrupt change of schedule, coincides with the period when natural light shrinks fastest. Both signals that keep the clock on time weaken at once.

Why it weighs more on some people than others

The strongest explanation for this difference is the dual vulnerability hypothesis, put forward by Michael Young and his team in the early 1990s and revisited by Lam et al. (2001) with 558 patients at a specialized clinic. It proposes two factors that combine:

• A vulnerability to seasonality, biological in origin: more sleep, more appetite, less energy when the light changes. Many people have it to a mild degree.
• A vulnerability to depression, both psychological and biological, which determines whether those physical symptoms stay a nuisance or turn into a drop in mood.

In the accounts of people with seasonal affective disorder, tiredness and extra sleep usually come first, and sadness and negative thoughts follow. That sequence is what interests psychology: what a person thinks and does about the tiredness is part of how it unfolds.

The psychological piece: rumination and beliefs about the season

The role of thoughts has been studied mainly in seasonal affective disorder. Kelly Rohan’s team at the University of Vermont designed a specific cognitive behavioral therapy (CBT-SAD) that works on behavioral activation during the darker months and on negative beliefs about winter (“I’m useless at this time of year”).

In their trial with 177 adults (Rohan et al., 2015), six weeks of this therapy and six weeks of bright morning light produced similar improvements. The follow-up (Rohan et al., 2016) found a difference two winters later: recurrence was 27.3% in the therapy group versus 45.6% in the light group. Light acts on the clock while it’s being used; therapy changes the way the season is interpreted, and that change seems to last.

These data come from people with a diagnosis, not from those who notice mild autumn fatigue, but the principle carries over well: the same tiredness weighs differently depending on whether it’s read as a temporary adjustment or as proof that something is wrong. In popular spirituality, Eckhart Tolle describes something similar under the name “pain-body”; research studies it as rumination, the habit of turning a discomfort over and over without resolving it, which is consistently associated with lower mood.

What research says about light and regularity

What the evidence supports, in descriptive terms:

• Morning light is the signal that stabilizes the clock most. Bright morning light is the reference treatment for seasonal affective disorder, and in the study by Lam et al. (2001) the response was even higher in subsyndromal cases (78%) than in full cases (66%), although it was an open trial without a placebo group.
• Regular sleep and wake times are associated with a more stable circadian rhythm.
• Keeping up meaningful activities during the darker months is one of the components Rohan’s therapy considers central.

A nuance worth knowing

Not all research confirms that mood in the general population changes with the seasons. The study by Traffanstedt, Mehta and LoBello (2016), with 34,294 American adults, found no relationship between the severity of depressive symptoms and season, latitude or sunlight. Its critics point out that it measured only classic depressive symptoms and not the ones most typical of seasonality, such as oversleeping or increased appetite.

Our reading: seasonality is real in part of the population, but the “autumn slump” is neither universal nor inevitable, and it’s very easy to blame the season for tiredness that has other causes.

When it isn’t autumn fatigue

Seasonal affective disorder, described by Norman Rosenthal in 1984, is a depression that recurs at the same time of year, with its own clinical criteria (Meesters and Gordijn, 2016). In addition, persistent tiredness can have many other causes, from anemia or hypothyroidism to accumulated sleep loss.

If the tiredness is intense, lasts more than a few weeks or comes with a very low mood, the right step is to consult a healthcare professional rather than assume it’s seasonal. If you’d like to explore how you relate to your natural rhythms, the chronotype test is a good starting point.

Sources

• Zhang, R., and Volkow, N. D. (2023). Seasonality of brain function: role in psychiatric disorders. Translational Psychiatry, 13, 65. https://doi.org/10.1038/s41398-023-02365-x
• Kasper, S., Wehr, T. A., Bartko, J. J., Gaist, P. A., and Rosenthal, N. E. (1989). Epidemiological findings of seasonal changes in mood and behavior: A telephone survey of Montgomery County, Maryland. Archives of General Psychiatry, 46(9), 823-833.
• Rosenthal, N. E., Sack, D. A., Gillin, J. C., Lewy, A. J., Goodwin, F. K., Davenport, Y., Mueller, P. S., Newsome, D. A., and Wehr, T. A. (1984). Seasonal affective disorder: A description of the syndrome and preliminary findings with light therapy. Archives of General Psychiatry, 41(1), 72-80.
• Khalsa, S. B. S., Jewett, M. E., Cajochen, C., and Czeisler, C. A. (2003). A phase response curve to single bright light pulses in human subjects. The Journal of Physiology, 549(3), 945-952.
• Phillips, A. J. K., Clerx, W. M., O’Brien, C. S., Sano, A., Barger, L. K., Picard, R. W., Lockley, S. W., Klerman, E. B., and Czeisler, C. A. (2017). Irregular sleep/wake patterns are associated with poorer academic performance and delayed circadian and sleep/wake timing. Scientific Reports, 7, 3216. doi:10.1038/s41598-017-03171-4
• Lam, R. W., Tam, E. M., Yatham, L. N., Shiah, I. S., and Zis, A. P. (2001). Seasonal depression: The dual vulnerability hypothesis revisited. Journal of Affective Disorders, 63(1-3), 123-132. doi:10.1016/S0165-0327(00)00196-8
• Rohan, K. J., Mahon, J. N., Evans, M., Ho, S. Y., Meyerhoff, J., Postolache, T. T., and Vacek, P. M. (2015). Randomized trial of cognitive-behavioral therapy versus light therapy for seasonal affective disorder: Acute outcomes. American Journal of Psychiatry, 172(9), 862-869. doi:10.1176/appi.ajp.2015.14101293
• Rohan, K. J., Meyerhoff, J., Ho, S. Y., Evans, M., Postolache, T. T., and Vacek, P. M. (2016). Outcomes one and two winters following cognitive-behavioral therapy or light therapy for seasonal affective disorder. American Journal of Psychiatry, 173(3), 244-251. doi:10.1176/appi.ajp.2015.15060773
• Traffanstedt, M. K., Mehta, S., and LoBello, S. G. (2016). Major depression with seasonal variation: Is it a valid construct? Clinical Psychological Science, 4(5), 825-834. doi:10.1177/2167702615615867
• Meesters, Y., and Gordijn, M. C. M. (2016). Seasonal affective disorder, winter type: current insights and treatment options. Psychology Research and Behavior Management, 9, 317-327.
• Tolle, E. (1999). The Power of Now: A Guide to Spiritual Enlightenment. New World Library / Namaste Publishing.