A recent article led by Dr. Debangan Dey, assistant professor in the Department of Statistics with the College of Arts & Sciences at Texas A&M University, found that daily outdoor temperature is associated with changes in mood, energy levels and sleep quality. The findings offer new insight into how environmental conditions interact with mental health, particularly for individuals living with mood disorders.
The research, published in the Journal of Affective Disorders, examined how daily temperature relates to emotional well-being across different seasons among people with and without mood disorders. The study was conducted by scientists at the National Institute of Mental Health’s Intramural Research Program (NIMH), where Dey previously served as a visiting fellow before joining Texas A&M. The research was led by Dr. Kathleen Merikangas, a distinguished National Institutes of Health investigator and chief of the Genetic Epidemiology Research Branch, in collaboration with Dr. Vadim Zipunnikov, professor of biostatistics at the Johns Hopkins Bloomberg School of Public Health.
“Humans are part of their environment,” Dey said. “Environmental factors like temperature and light affect us, and understanding those connections can help us better understand mental health.”
Tracking Mood in Real Time
To study these relationships, researchers followed more than 450 individuals ranging in age from 11 to 84. Participants reported their mood, anxiety levels, energy and sleep quality through smartphone-based surveys delivered multiple times per day using the REACH ecological assessment app developed at the NIMH Intramural Research Program (Husky et al., 2025).
These self-reports were paired with local outdoor temperature data, allowing researchers to examine how changes in temperature corresponded with daily emotional experiences. Using smartphone-based tools allows researchers to capture mental health patterns in real-world environments rather than laboratory settings.
Researchers also accounted for other factors known to influence mental health, including light exposure, age and sex. Even after adjusting those variables, temperature remained a significant factor in the analysis.
The strongest associations appeared during the transitional seasons of spring and fall, particularly among individuals with bipolar disorder and major depressive disorder. In spring, warmer temperatures were associated with better mood, higher energy and improved sleep quality in those groups, while similar patterns were not consistently observed among those without mood disorders.
In the fall, the pattern was more complex. Dey described it as a nonlinear relationship, with both warmer and cooler-than-typical temperatures linked to positive emotional outcomes among individuals with bipolar disorder.
“In spring, the results were more intuitive,” Dey said. “But in fall we saw that both warmer and cooler deviations from the seasonal average could have positive effects. That’s something we still need to understand better.”
Environmental Factors and Mental Health
The findings contribute to a growing body of research examining how environmental factors influence mental health. Seasonal mental health changes are often attributed primarily to reduced daylight during winter. This research suggests that temperature itself may play an independent role. Understanding those connections may become increasingly important as climate patterns shift.
“As climate change increases day-to-day temperature variability, understanding how environmental conditions influence mental health becomes a growing public health priority,” Merikangas, the study’s principal investigator, said.
In the future, environmental data could potentially be incorporated into digital mental health monitoring systems. Because weather patterns can be predicted in advance, researchers say that information could eventually help clinicians anticipate higher-risk periods for individuals with mood disorders.
At Texas A&M, Dey is exploring related work with Dr. Tyler Prochnow, assistant professor at the School of Public Health, whose SPACES Study (Social and Physical Activity Contexts in the Environment in Summer) examines how social networks and built environments influence physical activity and mental health among youth. The study follows middle school students over a one-week period, combining real-time smartphone surveys with wearable devices to track activity patterns and environmental exposures.
Expanding The Research
The study is part of a broader effort to understand what researchers call the environmental exposome — the collection of environmental factors that influence human health.
As part of that effort, smartphones and wearable devices are making it increasingly possible to collect real-time environmental data alongside behavioral indicators. These tools can track physical activity, sleep and light exposure, allowing researchers to better understand how people interact with their surroundings on a day-to-day basis.
"Our goal is to integrate data on temperature, light exposure, air pollution and green space with digital health technologies," Dey said. "By combining that environmental data with behavioral and physiological information, we can better understand how daily environments shape well-being."