Janzen, B. (2022). Temperature and mental health: Evidence from helpline calls. arXiv preprint arXiv:2207.04992.
Introduction
Climate change is often discussed in terms of its physical impacts—rising sea levels, extreme weather events, and agricultural disruptions. However, less attention has been paid to how climate change affects mental health. Benedikt Janzen's research paper from the University of Bern addresses this crucial knowledge gap by examining the relationship between ambient temperature and mental distress.
The study uses an innovative approach by analyzing data from TelefonSeelsorge, Germany's largest telephone counseling service, to understand how daily temperature fluctuations affect mental health in real-time. This approach provides insights into subclinical mental health issues that might not be captured in traditional healthcare settings, offering a more comprehensive picture of temperature's psychological impacts.
As global temperatures continue to rise due to climate change, understanding these effects becomes increasingly important for public health planning and climate adaptation strategies. The research reveals a U-shaped relationship between temperature and mental health, with both extremely hot and cold temperatures adversely affecting psychological well-being.
Research Context and Significance
Mental health disorders represent a growing global burden, affecting approximately one billion people worldwide. With climate change projected to increase temperature extremes, there's an urgent need to understand how these changes might exacerbate mental health challenges.
Relationship Between Temperature and Mental Health
Prior studies have widely examined the effect of climate anomalies and temperature fluctuations on mental health. For example, Burke et al. (2018) and Carleton (2017) investigate the causal link between higher temperatures and increased suicide rates, focusing on extreme temperature events. In addition, Mullins and White (2019) analyze how temperature affects the utilization of healthcare services. Although these studies provide important insights, they primarily rely on clinical records or suicide statistics—measures that capture only severe mental health outcomes and may overlook more widespread, subclinical distress.
The Use of Alternative Indicators
Researchers have pointed out that relying solely on clinical data or suicide counts might miss a broader picture of mental health issues in the population, due to underreporting or the inability to capture low-threshold service demands. Obradovich et al. (2018), for instance, use self-reported mental health measures to establish a link with temperature fluctuations, though these measures may be subject to reporting biases. In contrast, this paper uses telephone counseling (helpline) data, which offers several advantages: it can capture subclinical mental health distress, provide high spatial and temporal resolution, and reflect actual help-seeking behavior that is not limited to clinical diagnoses.
Exploring Underlying Mechanisms
Regarding the potential mechanisms through which temperature affects mental health, the literature suggests both direct and indirect pathways:
(1) Direct effects: Extreme temperatures may disturb physiological regulation and alter central neurological signaling (e.g., Lõhmus, 2018), directly impacting mood and cognitive function.
(2) Indirect effects: Temperature extremes can lead to sleep disturbances (Obradovich et al., 2017; Minor et al., 2022), reduce cognitive performance (Graff Zivin et al., 2018), or trigger stress and anxiety due to prolonged discomfort (Clayton, 2020). Additionally, other studies have examined how temperature affects social behavior, aggression, and physical health, which may indirectly impair mental health through social and psychological channels.
Climate Change and Public Health Costs
A broader body of research indicates that temperature anomalies not only affect individual health but also impose significant societal and economic costs. For instance, studies like Deschênes and Greenstone (2011) examine the relationship between temperature and mortality, while other works discuss how climate change impacts overall health and its economic consequences. This literature provides a broader context that supports the investigation of how warming trends and temperature extremes might exacerbate mental health issues, ultimately leading to increased social costs.
In summary, the literature review in this paper highlights that:
① Existing research has largely focused on the relationship between temperature extremes and severe mental health outcomes (such as suicide or hospitalizations) while often neglecting milder, subclinical mental distress.
② While self-reported data and clinical records each have their limitations, helpline data are introduced as a novel indicator that captures real-time, fine-grained help-seeking behavior related to mental health.
③ Both theoretical and empirical studies suggest that temperature may affect mental health through multiple mechanisms—direct physiological impacts and indirect effects via sleep, cognitive function, and social interactions—thereby providing a solid foundation for the mechanism analysis in this paper.
④ In the context of global warming, the negative mental health effects of temperature extremes are of increasing concern, as they may result in substantial public health and economic challenges that necessitate further investigation.
This literature review not only underscores the innovative contribution of using helpline data to study mental health impacts of temperature but also establishes the theoretical and empirical grounding for the subsequent analysis using high-resolution German data.
Previous research on temperature and mental health has been limited in several ways:
- Narrow geographic focus: Many studies examined single regions or countries
- Limited temperature range: Research often focused on only hot or cold extremes
- Restricted outcome measures: Studies typically relied on formal healthcare utilization data, missing those who don't seek professional help
- Limited causal inference: Many studies couldn't establish clear causality between temperature and mental health outcomes
Janzen's research addresses these limitations by:
Using a comprehensive dataset covering all of Germany
Examining the full temperature distribution
Utilizing helpline call data that captures individuals who may not seek formal healthcare
Employing rigorous econometric methods to establish causal relationships
This study contributes to multiple research fields, including climate economics, mental health economics, environmental health, and public health planning. It also connects to recent research using helpline data to monitor population mental health during crises, as demonstrated during the COVID-19 pandemic.
Methodology and Data Sources
The research combines several datasets to create a comprehensive analysis:
Data Collection
Helpline call data: 485,274 calls to TelefonSeelsorge from November 2018 to March 2020
Weather data: Daily temperature, precipitation, sunshine, wind, and humidity from German weather stations
Air pollution data: Daily PM2.5 levels from the German Federal Environmental Agency
Data Processing
The author matched helpline call locations with weather and air pollution data using inverse-distance weighting techniques. This geographic matching allows for precise analysis of how local environmental conditions affect mental health outcomes. The individual call data was aggregated to the daily level for statistical analysis.
Econometric Approach
The core methodology employs a panel fixed effects regression model:
log(Calls_ct) = f(Temperature_ct) + βX_ct + γ_c + δ_t + ε_ct
Where:
Calls_ct represents the number of calls from counseling center c on day t
f(Temperature_ct) is a flexible function capturing temperature effects
X_ct includes control variables like precipitation and air pollution
γ_c are counseling center fixed effects
δ_t are time fixed effects (year-month, day of week)
ε_ct is the error term
The model uses two-way clustering of standard errors at the counseling center and year-month level to account for correlated errors. The author conducted various robustness checks, including placebo tests and alternative model specifications, to validate the findings.
Key Findings
The study reveals several important findings about the relationship between temperature and mental distress:
U-shaped relationship: Call volume demonstrates a nonlinear, U-shaped relationship with temperature, with significantly higher call volumes on both extremely hot (>25°C/77°F) and cold (<0°C/32°F) days compared to moderate temperature days.
Magnitude of effects: Call volume is 3.4% higher on hot days and 5.1% higher on cold days compared to moderate temperature days (15-20°C/59-68°F). This translates to approximately 30-45 additional calls daily across Germany during temperature extremes.
Differential impacts by demographic groups:
Hot days primarily affect male callers
Cold days disproportionately impact older individuals
Hot days have a stronger effect on younger people
Call duration effects: As temperatures increase, call duration decreases. A 1°C increase in temperature leads to a 0.3% decrease in call length, suggesting that heat may affect not only the quantity but also the quality of mental health support.
Dynamic effects: Hot temperatures produce immediate adverse effects, while cold temperatures appear to have cumulative effects that build over several days, potentially due to prolonged social isolation during cold periods.
These findings confirm that temperature extremes have measurable, causal impacts on population mental health, with different mechanisms at work for hot versus cold temperatures.
Mechanisms Behind Temperature Effects
The research provides valuable insights into why temperature affects mental health by analyzing the topics of helpline calls:
Hot Temperature Mechanisms
Psychological well-being: Hot temperatures significantly increase calls related to mood disorders, anxiety, and stress. This aligns with biological research showing that heat can disrupt neurotransmitter function and hormonal balance.
Violence: Higher temperatures are associated with increased calls about violence and aggression. This supports the "heat hypothesis" in criminology, which suggests that hot temperatures increase irritability and aggressive behavior.
Reduced coping capacity: Heat may impair cognitive function and self-regulation, making it harder for individuals to cope with existing stressors.
Cold Temperature Mechanisms
Social isolation: Cold weather increases calls related to loneliness and social well-being, potentially because cold temperatures limit mobility and social interactions.
Compounding psychological effects: Cold periods are associated with increased calls about general psychological distress, suggesting broader impacts on mental well-being.
Seasonal affective disorder: While not directly measured in the study, the results are consistent with research on seasonal affective disorder, which is linked to reduced sunlight exposure during colder seasons.
Understanding these mechanisms is crucial for developing targeted interventions to protect vulnerable populations during temperature extremes.
Implications for Climate Change Adaptation
The research has significant implications for climate change adaptation strategies:
Projected mental health burden: As climate change increases the frequency and intensity of temperature extremes, the mental health burden is likely to grow substantially. This represents a previously underestimated social cost of climate change.
Targeted interventions: The differential impacts by demographic groups suggest the need for targeted interventions:
Older adults may need additional support during cold periods
Men may require specific mental health resources during heat waves
Young people may benefit from heat-focused coping strategies
Public health planning: Health systems should prepare for increased demand for mental health services during temperature extremes, including staffing helplines appropriately during these periods.
Urban design considerations: The findings support urban design approaches that mitigate extreme temperatures, such as green spaces and cooling centers, which may have mental health benefits beyond their physical health impacts.
Economic implications: The research suggests that climate change mitigation efforts should account for the mental health costs of temperature extremes in cost-benefit analyses, potentially strengthening the case for more aggressive climate action.
Strengths and Limitations
Strengths
Novel data source: The use of helpline data captures mental health impacts across the clinical spectrum, including individuals who don't seek formal treatment.
Comprehensive geographic and temperature coverage: The study examines all of Germany across the full temperature distribution.
Rigorous methodology: The econometric approach establishes causality through fixed effects and extensive controls.
Mechanism exploration: Analysis of call topics provides insights into the pathways through which temperature affects mental health.
Limitations
Limited timeframe: The study covers only 17 months, potentially missing longer-term temperature effects.
Single country focus: The research is limited to Germany, which may limit generalizability to regions with different climate patterns or cultural contexts.
Selection effects: Helpline callers may not be representative of the general population.
Limited socioeconomic data: The study couldn't analyze how socioeconomic factors might moderate temperature effects due to data limitations.
Conclusion
Benedikt Janzen's research provides compelling evidence that temperature extremes—both hot and cold—have significant negative impacts on mental health. The study reveals a U-shaped relationship between temperature and mental distress, with differential effects by age and gender. It also identifies distinct mechanisms through which hot and cold temperatures undermine psychological well-being.
These findings have important implications for climate change adaptation, suggesting that the mental health consequences of rising temperatures represent a substantial yet underappreciated social cost of climate change. Health systems will need to prepare for increased demand for mental health services during temperature extremes, and public health interventions should be tailored to protect vulnerable groups.
As global temperatures continue to rise, this research highlights the importance of incorporating mental health considerations into climate policy and adaptation strategies. By understanding the complex relationship between temperature and psychological well-being, we can better protect population mental health in a warming world.
The study also demonstrates the value of novel data sources like helpline calls for monitoring population mental health in real-time, providing an important model for future research in this critical area where climate science meets public health.
Relevant Citations
Alm 00e5s, I., Auffhammer, M., Bold, T., Bolliger, I., Dembo, A., Hsiang, S. M., . . . Pickmans, R. (2019). Destructive behavior, judgment, and economic decision-making under thermal stress.NBER Working Paper No. 25785.
This paper provides evidence of a causal link between temperature and destructive behavior in a laboratory setting. It suggests that hot temperatures might decrease patience and increase impatience, which could also have an impact on decision-making and behavior in real-world settings like helpline calls.
Baylis, P. (2020). Temperature and temperament: Evidence from Twitter.Journal of Public Economics,184, 104161.
This citation analyzes the relationship between temperature and expressed mood on Twitter, finding a U-shaped relationship where both hot and cold temperatures correlate with negative sentiment. This is relevant because the paper also finds a U-shaped relationship between temperature and helpline calls, suggesting a potential link between mood and help-seeking behavior.
Br 00fclhart, M., Klotzb 00fccher, V., Lalive, R., & Reich, S. (2021). Mental health concerns during COVID-19 as revealed through helpline calls.Nature,600, 1 20136.
This paper uses helpline data as a real-time proxy for monitoring population mental health during the COVID-19 pandemic. It is methodologically relevant to the user's paper, showing the utility of helpline data, and also shows the pandemic increased call volume and the need to limit the observation period.
Burke, M., Gonz 00e1lez, F., Baylis, P., Heft-Neal, S., Baysan, C., Basu, S., & Hsiang, S. (2018). Higher temperatures increase suicide rates in the United States and Mexico.Nature climate change,8(8), 723 2013729.
This article studies the impact of temperature on suicide rates and finds a linear relationship between temperature and suicidality, serving as a comparison point for the nonlinear results found in the user's paper. It is relevant as it links temperature to mental health outcomes.
Obradovich, N., Migliorini, R., Paulus, M. P., & Rahwan, I. (2018). Empirical evidence of mental health risks posed by climate change.Proceedings of the National Academy of Sciences,115(43), 10953 201310958.
This citation explores the relationship between temperature and self-reported mental health. This is relevant as it presents an alternative measure of mental health and shows similar nonlinear results to the user's paper, strengthening the argument for the U-shaped relationship between temperature and mental distress.
