The association between brain serotonin transporter binding and impulsivity and aggression in healthy individuals

The serotonin system plays a critical role in the modulation of impulsive aggression. Although serotonin transporters (SERT) are key in modulating synaptic serotonin levels, few studies have investigated the role of SERT levels in human impulsive aggression. The aim of this study was to investigate whether brain SERT levels are associated with trait impulsive aggression. We included 148 healthy individuals (mean age 29.3 ± 13.0, range 18-80 years, 91 females) who had undergone positron emission positron (PET) examinations with the SERT tracer [¹¹C]DASB and filled in self-report questionnaires of trait aggression, trait impulsivity and state aggression. We evaluated the association between cerebral SERT binding (BP_ND) and trait impulsive aggression in a latent variable model, with one latent variable (LV_SERT) modelled from SERT BP_ND in frontostriatal and frontolimbic networks implicated in impulsive aggression, and another latent variable (LV_IA) modelled from various trait measures of impulsivity and aggression. The LV_SERT was not significantly associated with the LV_IA (p = 0.8). Post-hoc univariate analyses did not reveal any significant associations between regional SERT levels and trait aggression, trait impulsivity or state aggression, but we found that state aggression at the day of PET scan was significantly lower in L_A/L_A homozygotes vs S-carriers of the 5-HTTLPR gene (p = 0.008). We conclude that brain SERT binding was not related to variations in trait impulsive aggression or state aggression. Our findings do not support that SERT is involved in mediating the serotonergic effects on aggression and impulsivity, at least not in individuals with non-pathological levels of impulsive aggression.