Digital health app users report increased bipolar depression correlated with worsening air quality

Air pollution has been shown to increase depression symptoms in individuals with bipolar disorder, a new study published by Cambridge University Press found.

Insights into the effects of pollution on mental health were gleaned from data from the Juli digital health app. The AI-powered chronic condition platform gives patients insight into their mental health in order to better manage their symptoms. Researchers at University College London found a positive correlation between poor air quality and depression through comparing geolocation data and depression symptoms as reported by Juli users.

“Where I live in London the air quality index (AQI) is probably 100 most of the time, but there'll be times when it goes a lot higher and so in those times you start to have a noticeable effect on individuals with bipolar disorder,” Joseph Hayes, M.D., Ph.D., chief study author and principal research fellow in psychiatry at UCL, told Fierce Healthcare. “There's also probably particular subtypes of bipolar disorder that we haven't really identified yet, as there are with depression, that are more inflammatory in nature, and it might be that pollution has a particular impact on those individuals.”

Hayes, along with other researchers, compared iPhone geolocation data and daily AQI data with answers to clinically validated questionnaires, which Juli users fill out biweekly. All 1,432 study participants were previously diagnosed with bipolar disorder.

Earlier research has confirmed that increases in AQI correlate with spikes in reported depression symptoms for people with unipolar depression. While the new research did prove the hypothesis that depression in individuals diagnosed with bipolar increased in a similar manner, AQI did not appear to increase symptoms of mania.

A detailed understanding of why the phenomenon takes place has yet to be determined. While recent occurrences of hazardous AQI along the East Coast have decreased visibility, Hayes said that the AQI-related depression is not tied to lack of sun exposure, as is the case in seasonal affective disorder. He also said that despite widespread concern over the state of climate change, he does not believe the change in depression symptoms to be related to any existential angst.

“Individuals wouldn't necessarily perceive a difference of 10 or 20 or 30 points in AQI, so you wouldn't necessarily know, 'OK, the air pollution is higher today, I should feel more anxious because this is a sign of this inevitable climate crisis',” Hayes said.

When it comes to recent events such as hell-scape smog conditions in New York, Hayes believes reported changes in depression related to large-scale fears of humanity’s future would present less acutely. Additionally, he believes no such dramatic climate events took place during the study period in the areas measured.

Hayes studies bipolar disorder and believes that recent studies are only the beginning of understanding how air quality affects mental health. Some of the pollutants measured and aggregated into the AQI score are capable of crossing the blood-brain barrier and therefore hold the potential for causing inflammation of the brain.

“We haven't got into very detailed understanding of what happens when something crosses the blood-brain barrier, its impacts on a neuron and how that links to how someone might present,” Hayes said. “So there's this whole sort of black box in between depression symptoms and the root cause. I think we're starting to unpick that, but that’s where we stop at the moment with this idea of inflammation. There's also some suggestion that it can have hormonal impact. So it might be that it's acting through multiple pathways.”

Hayes’ bipolar research stems from the use of big data via sources like electronic health records or, in this case, the Juli app. The AI-based app already utilizes predictive models to help users reduce symptoms of mania and depression. Insights like Hayes’ can make the app’s predictive powers even more robust.

Juli aggregates data from EHRs, smartphones, wearable devices and the environment to give users a global idea of the state and near future of their mental health. Users respond to three to five daily questions and biweekly clinically validated, condition-specific questionnaires to help tailor support.

Users receive suggestions on how to manage their overall health through behavioral changes and accessing healthcare. On days with poor AQI, users may be prompted to exercise at the gym as opposed to outdoors. In September of last year, the app released data that 55.5% of its users diagnosed with bipolar disorder reported a reduction in mania after using the app for eight weeks.  

Hayes hopes to continue working with the app on future research regarding the success of interventions. He imagines a future where physicians are also able to access patient information warning of a possible depressive episode or relapse.

“I suppose the other side of things is how you start to influence policy around this and obviously clean air and respiratory disease has been a big thing,” Hayes said. “But I think making people more aware about the mental health impacts potentially would affect policy.”

Bipolar disorder has been found to bring a substantial economic burden of care although just how much has yet to be determined. Per-person lifetime cost estimates have ranged from $11,720 to $624,785. Direct healthcare costs for those with bipolar are estimated to be $25 billion higher than the general population.

The financial and health costs of climate change have been trumpeted by experts for decades. The price of healthcare costs alone have been predicted to reach $860 billion, a report from the Natural Resources Defense Council, the Medical Society Consortium on Climate and Health and Wisconsin Health Professionals for Climate Action found.

Thousands of premature deaths were predicted in the 2021 study with many being tied to pollution and smog. Prospective premature deaths were also attributed to heatwaves, wildfires and hurricanes. Direct treatment costs and downstream medical costs are also expected to rise.