Surprising link observed between body temperature and depression

In a groundbreaking study that draws attention to the intersection between physiology and mental health, researchers have uncovered a link between depression and higher body temperatures. This discovery, published in Scientific Reports, not only deepens our understanding of depression but also hints at innovative treatments that might involve regulating body temperature to alleviate symptoms of the disorder.

The motivation behind this study was rooted in the alarming rise of depression rates globally and the pressing need for new treatment avenues. Depression, particularly major depressive disorder (MDD), has seen a surge in prevalence across various demographics, notably among youth and young adults in the United States.

This rise coincides with increased antidepressant usage, despite the limitations of these medications in terms of efficacy. Identifying physiological signatures unique to individuals with MDD could pave the way for developing targeted treatments, especially for those within a biologically homogeneous subgroup.

For their study, the researchers harnessed data from 20,880 individuals from the TemPredict Study, a prospective, worldwide cohort study initially designed to identify the onset of COVID-19 using physiological metrics collected by the Oura Ring, a wearable device. The TemPredict Study spanned several months, during which participants provided daily self-reported body temperature readings and completed monthly surveys assessing depression severity.

“To our knowledge, this is the largest study to date to examine the association between body temperature, assessed using both self-report methods and wearable sensors, and depressive symptoms in a geographically broad sample,” said Ashley Mason, an associate professor of psychiatry at UC San Francisco Weill Institute for Neurosciences and the study’s lead author. “Given the climbing rates of depression in the U.S., we’re excited by the possibilities of a new avenue for treatment.”

The use of the Oura Ring added a layer of precision and continuity to the data collection process. This wearable device, worn on the finger, measures distal body temperature every minute, providing a continuous stream of data on the participants’ thermal state. This allowed the researchers to analyze not just static temperature readings, but also the dynamic changes in temperature throughout the day and night.

The researchers found that higher levels of depressive symptoms were consistently associated with higher body temperatures. This correlation was observed across both self-reported data and minute-level temperature data collected by the Oura Ring. This pattern suggests a robust relationship between elevated body temperature and the presence of depressive symptoms, reinforcing the hypothesis that thermoregulatory dysregulation may play a role in depression.

“Though there are studies from decades ago documenting a correlation between depression and body temperature, those studies were small, often with 10-20 people in them,” Mason said. “This study that we have just published shows this correlation in a much larger sample, and will hopefully inspire more work into the mechanisms that underpin this correlation.”

Moreover, the analysis of wearable sensor data revealed nuanced details about the thermoregulatory patterns associated with depression. The study identified smaller differences between awake and asleep distal body temperatures in individuals with more severe depressive symptoms. This finding indicates that depression may affect the body’s ability to regulate temperature across different states of consciousness, potentially impacting the natural cooling processes that facilitate sleep onset and quality.

The consistency of these temperature elevations, particularly during periods that are crucial for thermoregulatory cooling, underscores the potential significance of body temperature as a physiological marker of depression.

Interestingly, the study also explored the diurnal amplitude of distal body temperature, which refers to the variation in temperature between daytime and nighttime. Participants with depression showed lower diurnal temperature amplitudes, suggesting a blunted circadian rhythm in body temperature. This aligns with previous research indicating circadian rhythm disturbances in depression and adds further evidence to the complex relationship between sleep, thermoregulation, and mood disorders.

The researchers noted the potential for decreased ability to induce thermoregulatory cooling or increased metabolic heat production, or a combination of both, as mechanisms underlying the observed temperature elevations in individuals with depression.

But the findings do not establish a causal relationship between body temperature and depression. The study was unable to determine whether elevated body temperatures contribute to the development or exacerbation of depressive symptoms, or if depression leads to an increase in body temperature due to altered metabolic or thermoregulatory processes.

Future research directions include exploring the underlying biological mechanisms of this association, examining the potential of temperature-based interventions for depression, and investigating the impact of controlled body temperature modulation on depressive symptoms.

“The link is particularly fascinating because there are data showing that when people recover from their depression – regardless of how they got better – their temperature tends to regularize,” Mason explained. “Then we have newer data suggesting that temperature-based interventions may reduce depression symptoms.”

“For example, data have shown that using heat-based treatments, in particular infrared sauna, cause acute increases in body temperature. These increases in body temperature engage the body’s self-cooling mechanisms (think, sweating) and can lead to subsequent decreases in body temperature (we sweat, we cool ourselves down).”

“And one study showed that decreases in a person’s body temperature in the days after a single heat treatment correlated with decreases in their depression symptoms over that same time period,” Mason continued. “So what’s exciting here is that the link might operate in multiple ways – what’s new is that we might be able to intervene directly on body temperature to address depression symptoms.”

“We are actively studying heat treatments, in particular sauna treatments, as a body-based intervention for depression symptoms here at UCSF in the heart of San Francisco. We have an ongoing trial right now for individuals with clinical depression where we are pairing sauna treatments with cognitive behavioral therapy for depression. Interested parties can learn more here: https://www.sealab.ucsf.edu/heatbedstudy.”

The study, “Elevated body temperature is associated with depressive symptoms: results from the TemPredict Study,” was authored by Ashley E. Mason, Patrick Kasl, Severine Soltani, Abigail Green, Wendy Hartogensis, Stephan Dilchert, Anoushka Chowdhary, Leena S. Pandya, Chelsea J. Siwik, Simmie L. Foster, Maren Nyer, Christopher A. Lowry, Charles L. Raison, Frederick M. Hecht, and Benjamin L. Smarr.