On the possibility to modulate psychopathic traits via non-invasive brain stimulation: A systematic review and...

The affective and interpersonal features of psychopathy describe impairments in socio-affective processes such as affective empathy, prosocial motivation and guilt. Research in neuroscience shows that these processes are associated with distinct neural circuits and cortical excitability patterns that appear to be dysregulated in individuals with psychopathy, with emerging research suggesting the potential of non-invasive brain stimulation (NIBS) to address such disruptions. To investigate this possibility, we conducted a meta-analysis of 64 sham- or active-controlled studies (122 effects) across three modalities: repeated transcranial magnetic stimulation (rTMS), theta-burst stimulation (TBS), and transcranial direct current stimulation (tDCS). Protocols were classified as excitatory (high-frequency rTMS, anodal tDCS) or inhibitory (low-frequency rTMS, continuous TBS, cathodal tDCS) depending on the expected polarity and directionality of their effects. Excitatory protocols yielded small-to-moderate improvements in socio-affective outcomes (Hedges' g ≈ 0.33-0.33), whereas only cathodal tDCS produced modest reductions among inhibitory protocols (g = -0.43). However, over 90 % of the included studies were conducted in healthy adult samples, limiting direct generalizability to psychopathy. In fact, the only available study in psychopathic individuals reported null effects. Together, these findings provide preliminary proof-of-concept for the potential of NIBS to modulate socio-affective processes relevant to psychopathy but also point to substantial methodological variability and the absence of direct evidence for psychopathy treatment in current research. Addressing these gaps is essential to evaluate the feasibility of implementing NIBS methods as a viable intervention for psychopathy.