Light, Air, and Mood: How Our Environments Shape Energy in Autumn
3 October 2025
As the days grow shorter, many of us notice a shift in energy, mood, and focus. Less daylight and more time spent indoors can change how we feel and how productive we are. While our habits certainly matter, research increasingly shows that our environment — light and air quality in particular — plays a central role in shaping wellbeing during seasonal transitions.
Light and Seasonal Mood
One of the most recognised seasonal influences on mental health is seasonal affective disorder (SAD), a form of depression that follows a predictable seasonal pattern. Reduced daylight in autumn and winter is a key driver, affecting circadian rhythms and the brain’s regulation of mood-related neurotransmitters.
Geographic and cultural studies of SAD emphasise how important the light environment is in shaping seasonal mood patterns. As Bodden (2024) notes, understanding SAD requires attention to the environments people live and work in — where access to light varies widely.
Air Quality and Mental Health
Light is not the only environmental factor influencing how we feel. Evidence linking air pollution and depression is growing stronger, with lots of new research emerging.
A comprehensive meta-analysis by Borroni et al. (2022) found consistent associations between exposure to fine particulate matter (PM2.5) and increased risk of depression. These tiny airborne particles, produced by traffic, industrial emissions, and everyday household activities, can penetrate into the bloodstream and reach the brain.
This body of evidence suggests that clean air is not only vital for physical health, but may also play an important role in supporting mental wellbeing.
Biological Mechanisms
How might air pollutants affect mood and cognition? Research summarised by Zundel et al. (2022) highlights several plausible pathways. Pollutants can trigger:
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Inflammation and oxidative stress, which can disrupt brain function,
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Activation of microglial cells, leading to neuroinflammation,
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Changes in brain structure and connectivity linked to emotional regulation.
These processes overlap with pathways implicated in depression and other mood disorders. While most research to date has focused on depression more generally, the biological plausibility extends to conditions like SAD.
Time Indoors and Indoor Air Quality
As daylight hours decrease, people inevitably spend more time indoors. This seasonal shift may increase exposure to indoor air pollutants, such as volatile organic compounds (VOCs) from furnishings and cleaning products, fine particles (PM2.5) from cooking or heating, and accumulated outdoor pollutants that enter the home.
Although research directly connecting indoor air quality and SAD is limited, it is reasonable to suggest that higher indoor exposure to pollutants during the darker months could interact with seasonal mood vulnerabilities. This is an emerging hypothesis that deserves further exploration. We wonder: how might air quality interact with seasonal mood and productivity?
Looking Forward
The evidence is strong that air pollution is linked to depression, and mechanistic research explains how pollutants affect the brain. SAD research shows that light environments are central to seasonal mood changes. What remains underexplored is the intersection: how increased time indoors, combined with indoor air quality, might influence seasonal affective disorder.
At Healthy Air Technology, we are keen to see these links studied in more detail, to better understand how environments — both light and air — shape our seasonal wellbeing.
Practical Implications
While the science continues to evolve, this season there are already simple steps we can take to support wellbeing in autumn and winter:
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Maximise natural light exposure, especially in the morning.
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Incorporate ‘micro-breaks’ into the day, get up and go outside.
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Improve indoor environments with clean, well-circulated air to reduce pollutant build-up.
References
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Bodden S. (2024). SAD Geographies: Making Light Matter.
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Borroni E. et al. (2022). Air pollution exposure and depression: A comprehensive systematic review and meta-analysis.
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Zundel C.G. et al. (2022). Air Pollution, Depressive and Anxiety Disorders, and Brain Pathways.
Photo by RDNE Stock project: https://www.pexels.com/photo/mother-and-child-sitting-on-a-wooden-bench-while-eating-6529659/
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