Massive Study Aims to Decode the Biology of Aggression Across Mental Disorders

Aggression is one of the most consequential and least understood symptoms in psychiatry. It appears across an astonishing range of diagnoses, from schizophrenia and borderline personality disorder to autism spectrum disorder, depression, ADHD, bipolar disorder, and substance dependence, and it is especially prominent in forensic patients and in people with conduct disorder or antisocial personality disorder. Yet despite its clinical and societal weight, the neurobiological machinery driving aggressive behavior in mental illness remains largely opaque. A new study protocol published in BMC Psychiatry by Ute Habel of RWTH Aachen University Hospital, Andreas Reif of Goethe University Frankfurt, Sabine Herpertz of Heidelberg University, and colleagues lays out an unusually ambitious plan to change that, describing a longitudinal, transdiagnostic cohort designed to identify what the researchers call biosignatures of aggression.

The scale of the initiative is striking. The collaborative research center, funded by the German Research Foundation under the designation SFB/TRR 379, will recruit 900 adults and 200 children and adolescents across three study sites in Frankfurt, Mannheim/Heidelberg, and Aachen, along with a satellite cohort of 150 forensic patients. A matched control group of 300 adults and 100 youth will provide comparison data. Participants between the ages of 10 and 40 will be followed annually for at least 3.5 years, with a planned total duration of 12 years, allowing researchers to track how aggressive behavior emerges, stabilizes, or fades across critical developmental transitions. The study is registered in the German Clinical Trials Register under DRKS00035731.

What makes the approach genuinely novel is its transdiagnostic framing. Rather than treating aggression as a feature of individual disorders, the investigators anchor their measurements in the National Institute of Mental Health’s Research Domain Criteria framework, specifically the negative valence system, which encompasses acute threat and frustrative non-reward, and the cognitive system, which covers cognitive control and self-regulation. The scientific consensus, the authors argue, is that aggressive behavior is largely determined by the processing of threat, frustration, and cognitive control. When sensitivity to threat-related cues is heightened, or neutral cues are misread as threatening, the acute threat system may over-activate and elicit anger or fear; whether that escalates into aggression depends on whether prefrontal control regions can counteract the limbic surge.

Functional neuroimaging research has lent substantial support to this imbalance model. In impulsive or reactive aggression, studies suggest attenuated top-down control from the prefrontal cortex paired with excessive bottom-up activity in limbic and reward regions. Abnormalities in fronto-limbic networks have been documented in borderline personality disorder and conduct disorder, while impairments in emotion processing and regulation networks contribute to heightened aggressiveness in ADHD, autism spectrum disorder, and disruptive behavior disorders. Children and adolescents with conduct disorder show altered fronto-limbic regulation, a pattern also observed in individuals with high trait aggression. The new study will test whether these system-level dysfunctions cut across diagnostic categories, forming shared mechanisms rather than disorder-specific quirks.

Genetics features prominently in the design. The heritability of aggressiveness has been estimated at 50 to 60 percent, rising even higher in individuals with severe aggressive behavior and high levels of callous-unemotional traits. Traditional candidate gene studies focusing on serotonergic and dopaminergic systems, stress hormones, and oxytocin have fallen short, because roughly half of the variance in aggressive behavior appears to reflect complex polygenic influences spanning thousands of polymorphisms. The team will therefore construct an aggression polygenic risk score from genome-wide data and examine its genetic correlation with psychiatric disorder risk scores from large consortia. A genome-wide analysis of more than 700 violent offenders has already suggested complex interactions with childhood stress, trauma, gender, and hormones, and a recent synthesis highlighted RBFOX1, an RNA-binding protein affecting the splicing and stability of thousands of gene transcripts, as a replicated candidate for aggressive behavior.

Hormones form another pillar. Testosterone concentrations are elevated in both female and male patients with borderline personality disorder, and the hormone is thought to modulate aggression by influencing key brain regions for social threat processing, including the amygdala, hypothalamus, and periaqueductal gray. The protocol calls for annual saliva sampling of testosterone, estradiol, progesterone, cortisol, and oxytocin, with additional challenge-based measurements taken before and after participants view violent film sequences inside the MRI scanner. Notably, the role of female-specific sex hormones in aggression has barely been studied, a gap the researchers intend to close. Reduced estrogen has been found in females with conduct disorder, and cortisol awakening responses were positively related to anger and aggressiveness in female patients with borderline personality disorder.

Environmental adversity receives equal weight. Adverse childhood experiences, including abuse and neglect as well as early exposure to harsh urban environments, are well-established risk factors for aggressive behavior and psychopathology, with the type and timing of adversity shaping later risk in distinct ways. The study will assess childhood trauma retrospectively and capture daily life prospectively through ecological momentary assessment, a smartphone-based system run on the open-source JTrack platform developed at Forschungszentrum Jülich. Participants will answer prompts twice a week on a randomized sparse schedule, and in intensive two-week bursts of five prompts per day following each MRI session, recording provocations, anger, stress, substance use, and social context as they unfold in real time. Paper diaries administered every four days will log conflicts and aggressive outbursts continuously throughout the funding period.

The neuroimaging protocol is equally comprehensive. Every participant will undergo 3-Tesla MRI including T1- and T2-weighted anatomical scans, multidirectional diffusion tensor imaging, resting-state functional MRI, and a naturalistic aggression-perception task in which they watch validated violent movie clips drawn from films such as Saving Private Ryan and Leon: The Professional, with age-appropriate clips from a German children’s television series used for participants under 16. Non-violent clips matched for duration and action intensity serve as controls. Beyond the brain, the study will even profile the gut microbiome, collecting annual stool samples for metagenomic sequencing alongside dietary questionnaires, reflecting growing interest in the microbiome’s connection to behavior.

The central hypothesis is bold: that combining questionnaire-based characterization of the negative valence and cognitive systems with genetic, hormonal, and brain measures will reveal up to six distinct clusters, or biosignatures, of aggression that cut across diagnostic categories. Power calculations indicate the planned sample of 1,100 participants is more than adequate, with simulation studies showing that even 160 individuals can suffice to identify four clusters when effect sizes are moderate to large. The researchers will use k-means, hierarchical, and Gaussian mixture clustering, validated through hold-out methods, and later apply machine-learning frameworks to predict individual trajectories and clinical outcomes, prioritizing features with effect sizes above 0.5 to maximize predictive accuracy.

The stakes extend well beyond taxonomy. Aggressive behavior in patients worsens treatment outcomes and carries heavy social, economic, and personal costs, yet current pharmaceutical and psychotherapeutic interventions remain insufficient, partly because aggression itself is rarely the explicit target of treatment. There is also a persistent gender bias: males show higher rates of direct physical aggression, but women predominantly display verbal and indirect aggression that is often overlooked, and the relative risk of offending can actually be higher in female patients compared to female controls. By following participants across adolescence and adulthood, tracking sex-specific developmental trajectories, and measuring everything from polygenic risk to momentary frustration, the consortium hopes to finally predict who is at risk, who is resilient, and precisely which neurobiological levers might one day be pulled to intervene before aggression becomes entrenched.

Subject of Research: Transdiagnostic neurobiological mechanisms of aggression in mental disorders across the lifespan

Article Title: Neuropsychobiological transdiagnostic risk mechanisms for aggression in mental disorders across the life span

Article References: Neuropsychobiological transdiagnostic risk mechanisms for aggression in mental disorders across the life span. (n.d.). https://doi.org/10.1186/s12888-026-08359-5

Image Credits: AI Generated

DOI: 10.1186/s12888-026-08359-5

Keywords: aggression, mental disorders, transdiagnostic research, RDoC, neuroimaging, polygenic risk scores, testosterone, childhood adversity, borderline personality disorder, longitudinal study, forensic psychiatry, gut microbiome