Mental health and air quality: an emerging literature

A growing body of research links air-quality exposures to outcomes outside the respiratory and cardiovascular literature. A 2019 systematic review and meta-analysis found that long-term exposure to fine particles (PM_2.5) was associated with a higher risk of depression, with more limited evidence for anxiety, and that short-term spikes in PM₁₀ were associated with suicide; the authors call for better studies to test whether the links are causal. Multiple cohort studies also link traffic-related air pollution to dementia incidence in older adults. The mechanisms are still being mapped (systemic inflammation, oxidative stress, possibly direct olfactory-pathway exposure of the brain to ultrafines).

The most-replicated indoor finding is on cognitive performance vs CO₂. The Allen 2016 Harvard COGfx study tested office workers in chambers at 550, 945, and 1,400 ppm CO₂. Cognitive function scores dropped 15% at 945 ppm and 50% at 1,400 ppm versus baseline, across nine cognitive domains. The Satish 2012 LBNL study found similar effects. These are not lab artifacts; they show up across multiple research groups.

What this means for the dashboard: chronic indoor CO₂ above 1,000 ppm is more than a "stuffy" description. A home office that sits at 1,200 ppm during a workday warrants a ventilation review alongside the cognitive research discussed here. Health Canada uses 1,000 ppm as a residential 24-hour guideline; ASHRAE 62.1 sets commercial ventilation rates and does not make that number a universal indoor limit. For populations already managing depression or anxiety, keeping occupied-room CO₂ low remains a practical ventilation goal, not a diagnosis or a sharp health threshold.

A note on caution. The mental-health literature on indoor air is younger than the respiratory literature; associations are robust but mechanisms are not fully nailed down, and causality vs confounding is still debated for some outcomes. The dashboard should not be used to diagnose mood disorders or cognitive decline; that is medical territory. What the dashboard can do is remove one large source of variance (chronic stuffy CO₂) from a person's environment, so that whatever else is going on can be characterized more cleanly.

This is environmental information, not medical advice. The dashboard's readings help you make decisions about the air in your space. They do not diagnose conditions, interpret symptoms, or replace conversations with your physician. If symptoms persist, worsen, or coincide with a known exposure, talk to a healthcare professional. See what Terrestream's advice covers.