The European Research Council (ERC) is funding a research project led by Prof. Dr. Andreas Meyer-Lindenberg, Chairman of the Board and Medical Director of the CIMH, with an Advanced Grant of 2.5 million euros. Over the course of five years, the project—titled HOTHEAD—will investigate why high temperatures promote aggressive behavior and which processes in the brain are responsible for this. The findings are expected to help develop strategies that will enable societies to better protect themselves against the consequences of global warming.

A well-known phenomenon with no conclusive explanation

It has been known since ancient times that heat promotes aggressive behavior, and this has found its way into everyday language through expressions such as “hothead.” Studies show a clear link between high temperatures and violent crime, suicides, and even wars. Since the consequences of violence cost societies worldwide more than 12 percent of their gross domestic product, and temperatures are projected to rise significantly by 2050 due to climate change—depending on the region—a better understanding of the underlying processes is urgently needed.

A Shift in Perspective: From Psychology to Neuroscience

With HOTHEAD, the CIMH research team is proposing a shift in perspective: Instead of explaining the phenomenon purely in psychological terms, the project focuses on the neural circuits that control aggression and temperature regulation in the brain. These circuits are evolutionarily ancient and very similar across many species—including mice, rats, dogs, and even fish. Since an increase in aggression due to heat has also been observed in these animals, the scientists hypothesize that there is a common biological mechanism linking heat and aggressive behavior, and they aim to directly demonstrate this for the first time.

From brain scans to urban planning—research at all relevant levels

To test this hypothesis, the researchers are combining a variety of modern methods. Using high-resolution functional magnetic resonance imaging (fMRI), they are first examining the brain regions responsible for threat perception, aggressive arousal, and the control of these responses in humans and in a rat model. At the same time, the team is studying, over the course of a year, how heat stress in everyday life affects stress, interpersonal closeness, and aggressive behavior. To do this, they are collecting data from 400 participants using smartphone sensors, skin thermometers, and smart rings. Artificial intelligence methods will then be used to identify different subtypes from this extensive data set, each of which reacts to heat in its own way—for example, with increased stress or impaired self-control. Randomized studies will subsequently test whether these reaction patterns can be specifically influenced through digital interventions. The goal of the project is to develop a globally applicable digital tool that will be integrated with open-source platforms for urban and resource planning to support municipalities in designing heat-resilient living environments.

“With HOTHEAD, we aim to demonstrate for the first time which mechanisms in the brain link heat and aggression,” says Prof. Dr. Andreas Meyer-Lindenberg. “If we understand these mechanisms, we can develop effective strategies to help people and cities cope with the consequences of a warmer world.”

Interdisciplinary Team at the CIMH, Open Science

The ERC’s Advanced Grants are awarded to distinguished researchers who have achieved outstanding research results throughout their careers. Prof. Dr. Andreas Meyer-Lindenberg is Chairman of the Board and Director of the CIMH, holds the Chair of Psychiatry and Psychotherapy at the Mannheim Medical Faculty of Heidelberg University, and was the founding spokesperson for the German Center for Mental Health (DZPG). In terms of citation frequency, he ranks among the top 1 percent of researchers worldwide in the field of psychiatry.

With its facilities for cohort management, high-field neuroimaging at 7 Tesla, and artificial intelligence, the CIMH offers ideal conditions for a challenging project of this magnitude. Several CIMH researchers are involved: Prof. Dr. Dr. Heike Tost, an expert in imaging techniques at the Department of Psychiatry and Psychotherapy and head of the Systemic Neuroscience in Psychiatry research group, is contributing to the high-field fMRI studies in humans. Prof. Dr. Valery Grinevich, head of the Neuropeptide Research Unit in Psychiatry, is contributing his expertise from animal research. Prof. Emanuel Schwarz, Director of the Hector Institute for Artificial Intelligence in Psychiatry (HITKIP), contributes expertise in AI-supported analysis of multimodal datasets. Prof. Dr. Ulrich Reininghaus, Director of the Department of Public Mental Health, contributes his many years of experience with mobile digital data collection and digital interventions in everyday life.

The project is firmly committed to open science: All data and analysis plans are to be made freely available in recognized databases so that the scientific community can benefit from the results.