Pre- and Postsynaptic Serotonergic Differences in Males with Extreme Levels of Impulsive Aggression Without Callous Unemotional Traits: A Positron Emission Tomography Study Using 11C-DASB and 11C-MDL100907

BackgroundImpulsive aggression (IA) in adults is associated with brain serotonin (5-HT) system abnormalities and is more common following childhood adversity. Within aggressive behavior, IA and callous unemotional (CU) traits are core components of differentiable factors with opposing 5-HT abnormalities. We aimed to investigate 5-HT abnormalities in IA and potential correlations with severity of childhood adversity while controlling for confounding 5-HT effects of high CU traits and mental disorders.MethodsHealthy male subjects (mean age 34 ± 9 years) without high CU traits were recruited with IA ratings in the high (n = 14) and low (n = 13) population extremes. Serotonin transporter (SERT) and 5-HT2A receptor availability was measured in multiple brain regions using positron emission tomography with 11C-DASB and 11C-MDL100907, respectively, and compared between high-IA and low-IA groups. Correlations were measured between SERT and 5-HT2A receptor availability, impulsivity and aggression, and childhood adversity.ResultsCompared with the low-IA group, SERT were significantly higher in brainstem regions in the high-IA group (by 29.0% ± 11.4%) and modestly lower across cortical regions (by 11.1% ± 6.0%), whereas 5-HT2A receptors were also modestly lower (by 8.6% ± 4.0%). Across all subjects, brainstem SERT were significantly positively correlated with impulsivity, aggression, and childhood trauma ratings. Within the high-IA group, higher brainstem SERT was most strongly predicted by severity of childhood trauma (r = .76 in midbrain).ConclusionsPre-and postsynaptic 5-HT differences are present in men with high levels of IA and are strongly suggestive of a persisting effect of childhood adversity on serotonergic neurodevelopment and emotional-behavioral control.