The Research Brief is a short take about interesting academic work.

The big idea

People who breathe polluted air experience changes within the brain regions that control emotions, and as a result, they may be more likely to develop anxiety and depression than those who breathe cleaner air. These are the key findings of a systematic review that my colleagues and I recently published in the journal NeuroToxicology.

Our interdisciplinary team reviewed more than 100 research articles from both animal and human studies that focused on the effects of outdoor air pollution on mental health and regions of the brain that regulate emotions. The three main brain regions we focused on were the hippocampus, amygdala and the prefrontal cortex.

In our analysis, 73% of the studies reported higher mental health symptoms and behaviors in humans and animals, such as rats, that were exposed to higher than average levels of air pollution. Some exposures that led to negative effects occurred in air pollution ranges that are currently considered “safe” by the Environmental Protection Agency’s standards. In addition, we discovered that 95% of studies examining brain effects found significant physical and functional changes within the emotion-regulation brain regions in those exposed to increased levels of air pollution.

Most of these studies found that exposure to elevated levels of air pollution is associated with increased inflammation and changes to the regulation of neurotransmitters, which act as the brain’s chemical messengers.

Why it matters

Research into the physical health effects associated with air pollution exposure, such as asthma and respiratory issues, have been well documented for decades.

But only over the last 10 years or so have researchers begun to understand how air pollution can affect the brain. Studies have shown that small air pollutants, such as ultrafine particles from vehicle exhaust, can affect the brain either directly, by traveling through the nose and into the brain, or indirectly, by causing inflammation and altered immune responses in the body that can then cross into the brain.

At the same time, researchers are increasingly documenting the association between air pollution and its negative effects on mental health.

Unfortunately, research suggests that air pollution will only worsen as climate change intensifies and carbon emissions remain unregulated.

For this reason, more research into the health effects of air pollution exposure that goes beyond respiratory health outcomes into the realm of biological psychiatry is badly needed. For instance, the neurobiological mechanisms through which air pollution increases risk for mental health symptoms are still poorly understood.

What still isn’t known

In addition to our primary findings, our team also identified some notable gaps within the research that need to be addressed in order to paint a fuller picture of the relationship between air pollution and brain health.

Relatively few studies examined the effects of air pollution exposure during early life, such as infancy and toddlerhood, and in childhood and adolescence. This is especially concerning given that the brain continues to develop until young adulthood and therefore may be particularly susceptible to the effects of air pollution.

We also found that within the studies investigating air pollution effects on the brain, only 10 were conducted in humans. While research on animals has extensively shown that air pollution can cause a host of changes within the animal brain, the research on how air pollution affects the human brain is much more limited. What’s more, most of the existing brain studies in humans have focused on physical changes, such as differences in overall brain size. More research is needed that relies on a technique called functional brain imaging, which could enable researchers like us to detect subtle or smaller changes that may occur before physical changes.

In the future, our team plans to use brain imaging methods to study how air pollution increases the risk of anxiety during adolescence. We plan to use a variety of techniques, including personal air monitors that children can wear as they go about their day, allowing us to more accurately assess their exposure.

Clara G. Zundel, Postdoctoral Research Fellow in Psychiatry and Behavioral Neurosciences, Wayne State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Depression is a costly and debilitating condition that profoundly influences a person’s quality of life. In 2020, more than 21 million adults in the U.S. reported having at least one major depressive episode in the previous year. Depression symptoms increased dramatically during the COVID-19 pandemic, and now affect nearly 1 in 3 American adults.

There are also many disparities in access to depression treatment. Clinicians are less likely to recognize and treat depressive symptoms in certain groups, including racial and ethnic minorities, men, older adults and people with language barriers. These disparities may be driven by poor patient-physician communication about mental health, cultural differences in discussing depressive symptoms, stigma around mental illness and limited available treatment options.

Limited time to discuss mental health symptoms in depth in primary care settings may also contribute to the depression treatment gap. As a researcher and primary care physician focused on improving access to mental health treatment, I have seen many patients struggle to have their depressive symptoms recognized by their clinicians and access quality care. Depression screening often only occurs when a clinician suspects the patient may have depression or when the patient specifically requests mental health care.

But making depression screening a routine practice could help reduce treatment disparities. In January 2016, the U.S. Preventive Services Task Force began recommending depression screening for all adults. In October 2022, given the mental health effects of the pandemic, it extended the recommendation to include screening all adolescents age 12 and up for depression and suicide risk during routine wellness checkups.

In our recent study, my team and I found that implementing universal, routine depression screening for adults in primary care is one way to make detection more equitable.

Depression screening in one large health system

The goal of our study was to evaluate whether the six primary care practices in the University of California, San Francisco health system had adopted routine depression screening for all their adult patients, and whether traditionally undertreated or untreated groups were being screened.

Medical assistants were asked to administer the screening test before patients saw their clinician. The clinician, after reviewing and discussing the results with the patient, could then arrange a follow-up appointment, prescribe a depression medication or submit a referral to a behavioral health specialist.

After two years, we analyzed data for 52,944 adult patients who had an appointment at one of the primary care clinics in that period. Screening rates were initially low – only 40.5% of patients were screened. Furthermore, men, older adults, racial and ethnic minorities, those with public health insurance, and those with language barriers were all less likely to be screened. For example, patients who spoke a Chinese language were almost half as likely to be screened as patients who spoke English.

However, with the UCSF health system’s coinciding focus on equity, screening rates increased to 88.8% by 2019. UCSF Health established a task force that met over the course of the project to discuss its progress, share best practices across primary care clinics and actively make adjustments to address screening disparities.

Overall, screening rates dramatically increased over those two years for all groups at risk of having their depression go unrecognized and untreated.

Improving depression care for all patients

Depression is a leading cause of disability worldwide. It can affect a person’s ability to manage other chronic conditions, and can lead to worsened disability and earlier death.

Our research found that increasing universal screening efforts can help reach groups that are less likely to be screened and treated for depression. We ensured that screening tools were available in other languages, clinical staff were periodically trained, and screening was integrated with routine clinical tasks. We also made sure that our efforts were aligned with the UCSF health system’s priorities, quality improvement efforts and reimbursement policies to reduce the burden of implementation and ensure sustainability.

While depression screening is necessary, it is not sufficient on its own to decrease care disparities for depression. Additional research is needed to see whether improved screening will lead to increased treatment and care engagement among at-risk groups.

Our team’s next steps are to evaluate whether a positive screen led to initiation of treatment for depression, and whether all patient groups were equally likely to engage in treatment. Our hope is that the lessons we learned from implementing routine depression screening in our primary care practices can encourage other health care systems around the country to do the same, and help better serve diverse patient populations.

Maria Garcia, Assistant Professor of Medicine, University of California, San Francisco

This article is republished from The Conversation under a Creative Commons license. Read the original article.