An ancient phenomenon, still poorly understood
Expressions such as “hothead,” “heated debate,” or “boiling atmosphere” have long suggested what empirical evidence increasingly confirms: elevated ambient temperatures are associated with higher rates of violent crime, increased incidence of suicide, and a heightened risk of conflict and war. Globally, the societal costs of violence are estimated to exceed twelve percent of gross domestic product. With ongoing climate change, this problem is expected to intensify. However, the neurobiological mechanisms by which heat may facilitate aggression remain poorly understood.
It is precisely this gap that the HOTHEAD project seeks to address. Over a five-year period, Prof. Dr. Andreas Meyer-Lindenberg and his team at the Central Institute of Mental Health (CIMH, Zentralinstitut für Seelische Gesundheit (ZI) Mannheim), part of the German Center for Mental Health (DZPG (Deutsches Zentrum für Psychische Gesundheit)) Mannheim–Heidelberg–Ulm partner site, aim to elucidate the neurobiological mechanisms linking heat exposure and aggressive behavior.
From animal models to urban environments
The research strategy is deliberately broad in scope. The observation that not only humans, but also mice, rats, dogs, and fish exhibit increased aggression at higher temperatures suggests the existence of an evolutionarily conserved biological mechanism. Accordingly, the project investigates both animal models and human participants using high-resolution 7-Tesla functional magnetic resonance imaging (7T-fMRI) to identify brain regions involved in threat perception, aggressive arousal, and inhibitory control, as well as the ways in which thermal stress modulates these neural circuits.
In parallel, the project follows 400 individuals over the course of one year in their everyday environments. Smartphone-based sensors, skin temperature monitors, and smart rings are used to assess how thermal load influences stress levels, interpersonal proximity, and aggressive behavior. Using artificial intelligence methods, the resulting dataset will be used to identify distinct response phenotypes, such as individuals who primarily experience heat-induced stress and those whose self-regulatory control is diminished under thermal strain. Randomized controlled trials will then examine whether digital interventions can effectively mitigate these responses.
Ultimately, the project aims to develop a globally applicable digital tool to assist municipalities in designing heat-resilient urban environments and infrastructure.
As Prof. Dr. Andreas Meyer-Lindenberg notes, “Through HOTHEAD, we aim to demonstrate for the first time the neurobiological mechanisms that link heat and aggression. By understanding these mechanisms, we can develop effective strategies enabling both individuals and cities to cope with the consequences of a warming world.”
Source: Press release of the Central Institute of Mental Health, Mannheim
