Summary: Days of extreme heat are associated with increased rates of emergency room visits for mental health-related disorders, specifically stress, anxiety, mood disorders, and substance use disorders.
Source: Boston University
During periods of extreme heat, clinicians should expect to see an increase in patients requiring mental health services, according to a new study led by Boston University School of Public Health researchers.
Published in the journal JAMA Psychiatry, the study found that days with higher-than-normal temperatures during the summer season in the United States were associated with increased rates of emergency department (ED) visits for any mental health-related condition, particularly substance use, anxiety and stress disorders, and mood disorders.
The impact of heat on physical health is well documented, but few studies have examined the effects of extreme heat on mental health. This nationwide study is the largest and most comprehensive analysis of daily ambient temperature and mental health-related ED visits among US adults of all ages. As days of extreme heat are expected to increase due to worsening climate change, the findings fill a critical gap in research and provide evidence-based support for proactive interventions and policy solutions that can reduce heat-related crises.
“Emergency department visits represent some of the costliest interactions within the healthcare system,” says study lead author Dr. Amruta Nori-Sarma, assistant professor of environmental health at BUSPH. “Addressing the needs of the most vulnerable to preempt some of these visits can have a positive impact on individual health and costs, as well as preserve healthcare resources for other emergencies.”
The new findings should prompt healthcare providers to prepare for an increased need in mental health services during times when extreme heat is predicted, Nori-Sarma says. “When heat waves are forecasted, clinicians and public health experts may use our findings to prepare especially for outreach to patients with existing mental health conditions.”
The general public can also benefit from this insight, says study senior author Dr. Gregory Wellenius, professor of environmental health and director of the Climate and Health Program at BUSPH.
“On days of extreme heat, it is important that we each take the precautions necessary to take care of ourselves and our loved ones,” he says, which can include checking on neighbors or family members who may be susceptible to health impacts of heat exposure.
For the study, Nori-Sarma and colleagues obtained medical claims data on mental health-related ED visits from OptumLabs Data Warehouse, which contains de-identified, longitudinal health information on more than 200 million commercial and Medicare Advantage enrollees throughout the US. The researchers analyzed approximately 3.5 million ED visits among 2.2 million adults ages 18 or older who had commercial or Medicare Advantage health insurance during the warm season (May to September) from 2010 to 2019.
Days of extreme heat—defined as temperatures above the 95th percentile of temperature distributions by county—were most strongly linked with ED visits for childhood-onset behavioral disorders and substance use disorders, followed by anxiety, stress-related, and somatoform disorders, and mood disorders. Extreme heat was also associated with ED visits for schizophrenia.
The researchers found that the impact of heat on mental health was similar across age groups, and evident in both men and women and in every region of the country. “These results show that heat can profoundly impact the mental health of people regardless of age, sex, or where they live,” says Wellenius.
The authors found the the impact of heat was slightly higher in the Northeast, Midwest, and Northwest. Although those regions generally have lower temperatures than the southeast or southwestern US, “that is exactly why the populations in these areas might suffer the most during times of high temperatures,” Nori-Sarma says.
“They don’t necessarily have the skills or resources in place to cope during times of extreme heat. Heat events will become even more extreme as the climate continues to warm, so it’s doubly important to identify the populations that are most vulnerable and to help them adapt to warmer summertime conditions.”
In future studies, the researchers aim to identify public health strategies that will help alert people to the risks posed by extreme heat and better protect the most vulnerable community members. Subsequent research will also explore the impact of elevated temperatures on mental health during longer periods of time (i.e. heat waves), as well as the impact on vulnerable groups that this study did not assess, including the uninsured, low-income, and various race/ethnicities, and those experiencing less urgent situations.
The continuing effects of COVID-19 on mental health will also shape this work. Lockdowns, social isolation, and general uncertainty during the early days of the pandemic increased the need for—and limited the availability of—mental health services simultaneously as EDs were overwhelmed with patients experiencing physical emergencies, Nori-Sarma says.
“As we approach the upcoming summer season, it is important to keep in mind that the combination of stressors—pandemic and climate—might exacerbate existing mental health conditions,” she says. “The mental healthcare system should plan accordingly.”
Association Between Ambient Heat and Risk of Emergency Department Visits for Mental Health Among US Adults, 2010 to 2019
The implications of extreme heat for physical health outcomes have been well documented. However, the association between elevated ambient temperature and specific mental health conditions remains poorly understood.
To investigate the association between ambient heat and mental health–related emergency department (ED) visits in the contiguous US among adults overall and among potentially sensitive subgroups.
Design, Setting, and Participants
This case-crossover study used medical claims data obtained from OptumLabs Data Warehouse (OLDW) to identify claims for ED visits with a primary or secondary discharge psychiatric diagnosis during warm-season months (May to September) from 2010 through 2019. Claims for adults aged 18 years or older with commercial or Medicare Advantage health insurance who were living in 2775 US counties were included in the analysis. Emergency department visits were excluded if the Clinical Classifications Software code indicated that the visits were for screening for mental health outcomes and impulse control disorders.
County-specific daily maximum ambient temperature on a continuous scale was estimated using the Parameter-Elevation Relationships on Independent Slopes model. Extreme heat was defined as the 95th percentile of the county-specific warm-season temperature distribution.
Main Outcomes and Measures
The daily incidence rate of cause-specific mental health diagnoses and a composite end point of any mental health diagnosis were assessed by identifying ED visit claims using primary and secondary discharge diagnosis International Classification of Diseases, Ninth Revision and International Statistical Classification of Diseases and Related Health Problems, Tenth Revision codes. Conditional logistic regression models were used to estimate the incidence rate ratio (IRR) and 95% CIs for the association between daily temperature and incidence rates of ED visits.
Data from 3 496 762 ED visits among 2 243 395 unique individuals were identified (56.8% women; mean [SD] age, 51.0 years); of these individuals, 14.3% were aged 18 to 26 years, 25.6% were aged 27 to 44 years, 33.3% were aged 45 to 64 years, and 26.8% were aged 65 years or older. Days of extreme heat were associated with an IRR of 1.08 (95% CI, 1.07-1.09) for ED visits for any mental health condition. Associations between extreme heat and ED visits were found for specific mental health conditions, including substance use disorders (IRR, 1.08; 95% CI, 1.07-1.10); anxiety, stress-related, and somatoform disorders (IRR, 1.07; 95% CI, 1.05-1.09); mood disorders (IRR, 1.07; 95% CI, 1.05-1.09); schizophrenia, schizotypal, and delusional disorders (IRR, 1.05; 95% CI, 1.03-1.07); self-harm (IRR, 1.06; 95% CI, 1.01-1.12); and childhood-onset behavioral disorders (IRR, 1.11; 95% CI, 1.05-1.18). In addition, associations were higher among men (IRR, 1.10; 95% CI, 1.08-1.12) and in the US Northeast (IRR, 1.10; 95% CI, 1.07-1.13), Midwest (IRR, 1.11; 95% CI, 1.09-1.13), and Northwest (IRR, 1.12; 95% CI, 1.03-1.21) regions.
Conclusions and Relevance
In this case-crossover study of a large population of US adults with health insurance, days of extreme heat were associated with higher rates of mental health–related ED visits. This finding may be informative for clinicians providing mental health services during periods of extreme heat to prepare for increases in health service needs when times of extreme heat are anticipated.
About this mental health research news
Original Research: Open access.
“Association Between Ambient Heat and Risk of Emergency Department Visits for Mental Health Among US Adults, 2010 to 2019” by Amruta Nori-Sarma et al. JAMA Psychiatry