Quick answer: Seasonal affective disorder (SAD) is a form of depression that follows a seasonal pattern, usually appearing in autumn and winter as daylight hours shrink. In Australia, clinically diagnosed SAD is considered rare, but milder winter low mood is common, especially in southern cities like Melbourne. Evidence-based help includes daylight exposure, light therapy, regular exercise, a steady sleep routine and psychological therapies such as CBT.
Seasonal affective disorder (SAD) is a form of depression that comes and goes with the seasons. Most commonly it appears in the cooler, darker months and eases as the days lengthen again in spring (healthdirect, 2024). A less common summer pattern also exists.
To be diagnosed with SAD, the same seasonal pattern usually needs to be present for at least two years in a row (healthdirect, 2024). It is considered a subtype of depression rather than a separate illness — which means the low mood is genuine and can affect your sleep, energy, appetite and motivation, not simply a case of disliking the cold.
Many of us feel a little flatter in winter — we go out less, crave comfort food and want to hibernate. These “winter blues” are common and usually mild, and they don’t stop you living your life.
SAD is different. It meets the criteria for a depressive episode: the low mood is persistent, lasts most of the day for weeks at a time, and interferes with work, study, relationships or self-care. If your winter dip is manageable and lifts when the sun comes out for a day, it is more likely the winter blues. If it is heavy, ongoing and hard to shift, it may be something more — and it is worth checking in with a professional.
Winter-pattern SAD tends to look like depression with a distinctive “slowed-down” flavour. Common signs include:
These symptoms typically build in late autumn and winter and ease again in spring (Beyond Blue, 2025).
The leading explanation is light. Shorter days and less morning sunlight can disrupt your circadian rhythm — the internal 24-hour “body clock” that helps regulate sleep, energy and mood (healthdirect, 2024).
Reduced light exposure is linked to changes in two key brain chemicals. Your body may produce more melatonin (the hormone that makes you sleepy) and less serotonin (which helps regulate mood), which together can leave you feeling tired, low and out of sync (Beyond Blue, 2025). Lower winter sun also means less vitamin D, which some research links to mood — though the evidence here is still developing.
Because sleep and mood are so closely tied, a disrupted body clock can also worsen sleep quality. If winter is scrambling your nights, our guide to REM sleep and how to sleep better has practical steps that support both.
This is where Australia differs from the northern hemisphere. Because we sit closer to the equator than places like northern Europe or Canada, clinically diagnosed SAD is considered rare here (healthdirect, 2024; Beyond Blue, 2025). SAD is generally more common the further you live from the equator, where winters are darker and longer.
That said, “rare” does not mean “never”. Australian research suggests seasonal mood changes do occur, and are more noticeable in the country’s higher-latitude southern regions. Estimates vary widely by location and by how the condition is measured, with the highest rates reported in the far south, such as Tasmania (Nevarez-Flores et al., 2023). Melbourne — with its cold, grey winters and shorter July days — sits in that southern band, so while true SAD may be uncommon, winter low mood here is real and worth taking seriously.
The good news is that seasonal low mood responds well to practical, evidence-based steps. Approaches worth trying include:
If your low mood has lasted more than two weeks, is affecting your work, study, relationships or daily functioning, or returns at the same time each year, it is worth speaking with a professional. A GP can talk through your options and, if helpful, prepare a Mental Health Care Plan that gives you Medicare-subsidised sessions with a psychologist.
Winter low mood can also overlap with stress and anxiety; if that resonates, our guide to understanding anxiety and stress may help. You don’t need to wait until things feel unbearable to reach out — earlier support is easier support.
If you are ever feeling unsafe or thinking about suicide, please contact Lifeline on 13 11 14 or Beyond Blue on 1300 22 4636 for immediate support.
Beyond Blue. (2025). Types of depression. Beyond Blue. https://www.beyondblue.org.au/mental-health/depression/types-of-depression
Black Dog Institute. (2025). Depression: Help and support. Black Dog Institute. https://www.blackdoginstitute.org.au/resources-support/depression/help-support/
healthdirect. (2024). Seasonal affective disorder (SAD). Healthdirect Australia. https://www.healthdirect.gov.au/seasonal-affective-disorder
Lam, R. W., Levitt, A. J., Levitan, R. D., Enns, M. W., Morehouse, R., Michalak, E. E., & Tam, E. M. (2006). The Can-SAD study: A randomized controlled trial of the effectiveness of light therapy and fluoxetine in patients with winter seasonal affective disorder. American Journal of Psychiatry, 163(5), 805–812. https://doi.org/10.1176/ajp.2006.163.5.805
Nevarez-Flores, A. G., Bostock, E. C. S., & Neil, A. L. (2023). The underexplored presence of seasonal affective disorder in the southern hemisphere: A narrative review of the Australian literature. Journal of Psychiatric Research, 162, 170–179. https://doi.org/10.1016/j.jpsychires.2023.05.003
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