Normative Modeling Reveals Functional Connectivity Heterogeneity and Subtypes in Internet Gaming Disorder

Abstract Background Internet gaming disorder (IGD) is associated with abnormal functional connectivity (FC) in brain networks. However, findings from resting-state fMRI (RS-fMRI) studies are highly inconsistent, likely due to individual heterogeneity in IGD-related neural alterations—a feature commonly observed in other psychiatric disorders but understudied in IGD. Methods We applied normative modeling to RS-fMRI data to characterize individualized FC deviations between the nucleus accumbens (NAcc) and the rest of the brain in 173 IGD participants. Using a large sample of healthy controls (N = 232) to establish age- and sex-adjusted normative ranges, we quantified the abnormality of each IGD individual’s FC profile. Further, we performed k-means clustering on deviation values within the frontoparietal network (FPN) and basal ganglia network (BGN) to identify neurobiological subtypes. Results Our findings revealed considerable heterogeneity in FC abnormalities among IGD participants. Only a minority showed strong and widespread deviations, while most exhibited mild but diverse patterns. Clustering analysis identified five distinct IGD subtypes with varying hyper- and hypoconnectivity profiles in FPN and BGN. Conclusions These results highlight the heterogeneous neural basis of IGD and underscore the limitations of group-level comparisons. Normative modeling and FC-based subtyping offer a promising direction for individualized assessment and may inform personalized interventions, such as connectivity- and frequency-specific TMS targeting cognitive control and reward circuits.