Scholars have established subcategories of aggressive behavior in order to better understand this construct. Specifically, a classification based on motivational underpinnings makes it possible to differentiate between reactive and proactive aggression. Whereas reactive aggression is characterized by emotional lability, which means it is prone to impulsive reactions after provocation, proactive aggression is driven by low emotionality and high levels of instrumentality to obtain benefits. Some authors have conceived these two types as having a dichotomous nature, but others argue against this conceptualization, considering a complementary model more suitable. Hence, neuroscientific research might help to clarify discussions about their nature because biological markers do not present the same biases as psychological instruments. The main objective of this study was to carry out a systematic review of studies that assess underlying biological markers (e.g., genes, brain, psychophysiological, and hormonal) of reactive and proactive aggression. To carry out this review, we followed PRISMA quality criteria for reviews, using five digital databases complemented by hand-searching. The reading of 3993 abstracts led to the final inclusion of 157 papers that met all the inclusion criteria. The studies included allow us to conclude that heritability accounted for approximately 45% of the explained variance in both types of aggression, with 60% shared by both, especially, for overt and physical expression forms, and 10% specific to each type. Regarding allelic risk factors, whereas low functioning variants affecting serotonin transport and monoaminoxidase increased the risk of reactive aggression, high functioning variants were associated with proactive aggression. Furthermore, brain analysis revealed an overlap between the two types of aggression and alterations in the volume of the amygdala and temporal cortex. Moreover, high activation of the medial prefrontal cortex (PFC) facilitated proneness to both types of aggression equally. Whereas stimulation of the right ventrolateral (VLPFC) and dorsolateral (DLPFC) reduced proneness to aggression, inhibition of the left DLPFC increased it. Finally, psychophysiological and hormonal correlates in general did not clearly differentiate between the two types because they were equally related to each type (e.g., low basal cortisol and vagal variability in response to acute stress) CONCLUSIONS: This study reinforces the complementary model of both types of aggression instead of a dichotomous model. Additionally, this review also offers background about several treatments (i.e., pharmacological, non-invasive brain techniques…) to reduce aggression proneness.

Testosterone to cortisol (T/C) ratios could be associated with feelings and expression of anger as high testosterone and low cortisol levels indicate a predisposition to violence. The basal T/C ratio has recently been proposed as a marker for proneness to social aggression; so far, however, only its value as an indicator of state anger or violence has been investigated. Given this, we aimed to establish whether the T/C ratio response to acute stress was a specific psychobiological feature in individuals with a history of violence, namely, perpetrators of intimate partner violence (IPV). T/C ratio and anger responses were compared in men jailed for IPV and controls using the Trier Social Stress Test. IPV perpetrators had higher T/C ratios than controls, during the preparation period, and 15 and 30 minutes post-task. In IPV perpetrators, high T/C ratios were linked to better self-esteem and good mental health. An increase in anger may increase proneness to violence by altering hormones and, thereby, increasing T/C ratios. The basal T/C ratio together with acute stress responses and other indicators could serve as a marker to identify men at high risk of reacting violently to their partners.

Antisocial, borderline, and narcissistic personality traits have been described as characteristics of intimate partner violence (IPV) perpetrators. Furthermore, deficits in cognitive empathy and impairments in emotional decoding processes may at least partially explain conduct disorders and social dysfunction in general. However, previous research has not explored potential associations between empathy deficits and the aforementioned traits or whether they are reflected in recidivism in IPV perpetrators. Accordingly, the main aim of this study was to explore associations between empathy deficits, antisocial, borderline, and narcissistic traits and the risk of recidivism in this population. The sample consisted of 144 IPV perpetrators (mean age = 41 years). High antisocial and borderline personality traits in this sample were associated with a high risk of recidivism, these relationships being moderated by poor empathy skills. Moreover, in IPV perpetrators with both antisocial and borderline personality traits, the risk of recidivism was higher than in those with only one of these traits. In contrast, narcissistic traits were unrelated to the risk of recidivism and impairments in empathy. The results of our study highlight the importance of empathy deficits and may help professionals to develop specific intervention programs focusing on improving empathy skills in antisocial and borderline IPV perpetrators.

Research assessing the effectiveness of intervention programs for intimate partner violence (IPV) perpetrators has increased considerably in recent years. However, most of it has been focused on the analysis of psychological domains, neglecting neuropsychological variables and the effects of alcohol consumption on these variables. This study evaluated potential neuropsychological changes (emotional decoding, perspective taking, emotional empathy and cognitive flexibility) and their relationship with alcohol consumption in a mandatory intervention program for IPV perpetrators, as well as how these variables affect the risk of IPV recidivism. The sample was composed of 116 individuals with high alcohol (n = 55; HA) and low alcohol (n = 61; LA) consumption according to self-report screening measures who received treatment in a IPV perpetrator intervention program developed in Valencia (Spain). IPV perpetrators with HA consumption were less accurate in decoding emotional facial signals and adopting others’ perspective, and less cognitively flexible than those with LA consumption before the IPV intervention. Further, the effectiveness of the intervention program was demonstrated, with increases being observed in cognitive empathy (emotional decoding and perspective taking) and in cognitive flexibility. Nevertheless, the HA group showed a smaller improvement in these skills and higher risk of IPV recidivism than the LA group. Moreover, improvement in these skills was related to a lower risk of IPV recidivism. The study provides guidance on the targeting of cognitive domains, which are key factors for reducing IPV recidivism.