Feeling unusually tired, irritable, or unmotivated this October? The problem might not be your workload. A study involving 103 adults identified different sleep and circadian rhythm patterns associated with seasonal depression. Now, an October 23 warning from the University of Alabama at Birmingham explains why shorter fall days can affect mental health before winter arrives.

Stephen Thomas, PhD, associate professor of psychiatry and behavioral neurobiology at the University of Alabama at Birmingham, says seasonal affective disorder (SAD) doesn’t always begin with sadness. Changes in energy, sleep, appetite, and motivation can be warning signs. With daylight saving time ending November 1, the timing matters, although the clock change itself isn’t the primary cause.

Next: Common Habit After Dark Linked to 30% Higher Depression Risk, Study Finds

Why Shorter Days Can Change Your Mood

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Less sunlight can disrupt biological systems governing sleep and emotional regulation.…