A recent study published in JAMA Psychiatry has identified three distinct neurobiological biotypes of Attention-Deficit/Hyperactivity Disorder (ADHD) using a novel data-driven approach. Moving away from the traditional Diagnostic and Statistical Manual of Mental Disorders (DSM), which classifies the condition based on observed symptoms, researchers utilized a brain-first methodology to uncover unique subtypes with specific neurochemical signatures. This shift aims to address the oversimplification of ADHD as a uniform disorder and provide a more accurate biological understanding. The research team conducted an extensive analysis of MRI data from 1,831 participants collected across 10 different research sites. To ensure robustness, the dataset was divided into a discovery group of 1,154 individuals and an independent validation group of 677 participants. The study employed morphometric similarity networks, a technique that maps structural similarities among brain regions to view the brain as an interconnected network, alongside advanced data-clustering algorithms known as HYDRA. This approach allowed researchers to examine how different brain parts work together, overcoming limitations of previous imaging studies that often focused on isolated regions. The analysis revealed three distinct biotypes, each associated with different brain circuits and clinical presentations. Biotype 1 is characterized by widespread changes in the Medial Prefrontal Cortex–Globus Pallidus circuit and presents with severe combined symptoms including emotional dysregulation. Biotype 2 shows alterations in the Anterior Cingulate Cortex–Globus Pallidus circuit and is associated with predominantly hyperactive and impulsive behaviors. Biotype 3 is linked to changes in the Superior Frontal Gyrus and corresponds to predominantly inattentive symptoms. These findings suggest that ADHD is not a single entity but a heterogeneous condition with multiple underlying neural mechanisms. Previous attempts to define subtypes relied heavily on symptom checklists, which often merely categorized patients by the severity of their symptoms rather than biological differences. By utilizing a brain-first route, this study successfully separated ADHD into meaningful subgroups based on neurobiology. The development of a normative model within the study further enabled the identification of atypical biological features by comparing individual participants against a reference population, confirming the reliability of the three identified biotypes. These discoveries mark a significant advancement in understanding the complex nature of ADHD. The study highlights the potential to move beyond one-size-fits-all diagnostic labels and treatments. By identifying specific brain patterns associated with each biotype, clinicians may soon be able to offer personalized interventions tailored to an individual's underlying brain profile. This precision medicine approach could significantly improve treatment outcomes for the diverse population affected by the disorder. The findings were detailed in the article Attention-Deficit/Hyperactivity Disorder (ADHD) Biotype Identification Based on Heterogeneity Through Discriminative Analysis Modeling, available in the 2026 issue of JAMA Psychiatry.