Non-Invasive Brain Stimulation for the Modulation of Aggressive Behavior-A Systematic Review of Randomized Sham-Controlled Studies

Abstract

Intro: Aggressive behavior represents a significant public health issue, with relevant social, political, and security implications. Non-invasive brain stimulation (NIBS) techniques may modulate aggressive behavior through stimulation of the prefrontal cortex.

Aims: To review research on the effectiveness of NIBS to alter aggression, discuss the main findings and potential limitations, consider the specifics of the techniques and protocols employed, and discuss clinical implications.

Methods: A systematic review of the literature available in the PubMed database was carried out, and 17 randomized sham-controlled studies investigating the effectiveness of NIBS techniques on aggression were included. Exclusion criteria included reviews, meta-analyses, and articles not referring to the subject of interest or not addressing cognitive and emotional modulation aims.

Conclusions: The reviewed data provide promising evidence for the beneficial effects of tDCS, conventional rTMS, and cTBS on aggression in healthy adults, forensic, and clinical samples. The specific stimulation target is a key factor for the success of stimulation on aggression modulation. rTMS and cTBS showed opposite effects on aggression compared with tDCS. However, due to the heterogeneity of stimulation protocols, experimental designs, and samples, we cannot exclude other factors that may play a confounding role.

Keywords: aggression; cTBS; non-invasive brain stimulation; rTMS; tDCS.

Figure 1

Lateral, orbital and medial surfaces of the frontal lobe in the cytoarchitectonic atlas of Petrides and Pandya [37,38]. In the present figure, the various areas in the different regions are outlined as indicated below. (A) Lateral aspect of the frontal lobe. The outline of the dorsolateral prefrontal cortex (DLPFC) is indicated by the white dashed lines. The outline of the ventrolateral prefrontal cortex (VLPFC) is indicated by the yellow outline. Notice that the VLPFC can be viewed also from the orbital aspect, but it is not part of the orbital frontal cortex. (B) Orbital aspect of the frontal lobe. The cortex on the orbital surface includes areas 14 and 11 and also the orbital extension of frontopolar area 10 and ventromedial area 14. (C) Medial aspect of the frontal lobe. The dorsomedial prefrontal cortex (DMPFC) includes medial areas 8 and 9. The anterior cingulate region (ACC) includes areas 24 and 32. The ventromedial prefrontal cortex (VMPFC) is area 14.

Figure 2

Flow chart for eligible study selection. Seventeen articles were selected as suitable based on the eligibility criteria. Studies not related to the purpose of the review were excluded. One article was identified using the citation list of already included articles.