Intimate partner violence is a serious public health issue. In the United States, at least half a million women are victims of intimate partner violence annually—4.3 per thousand women.1
Women assaulted by an intimate partner experience significant health consequences including injury, chronic pain, gastrointestinal problems, sexually transmitted infections, depression, suicidality, post-traumatic stress disorder, and death.2
Efforts to understand the etiology of intimate partner violence are critical to reduce this health threat.
Though many studies have examined consequences of intimate partner violence victimization, relatively few studies have focused on risk factors for perpetrating such violence. Perpetration has been associated with low socioeconomic status,3
and poor parenting in childhood.4
The central theme in this literature, however, is the possible intergenerational transmission of violence, whereby witnessing intimate partner violence in childhood4-6
or experiencing physical abuse7
leads to perpetration of intimate partner violence in adulthood.
Three strands of evidence support a causal relationship between witnessing intimate partner violence in childhood and perpetrating such violence in adulthood: (1) consistency of association across a large number of studies in different populations; (2) theoretical plausibility; and (3) evidence supporting the mechanisms described in the theoretical models.
The association between witnessing intimate partner violence and later perpetration has been found in multiple studies in diverse settings,6,8
although some studies found no association.9,10
A meta-analysis of 39 studies found the strength of the association to be small-to-moderate.6
Theoretical models further support a causal relationship between witnessing intimate partner violence and later perpetration. Social cognitive models emphasize that children learn to perpetrate intimate partner violence by observing and imitating such violence in their childhood homes, without developing nonviolent conflict resolution and verbal skills.11
focus on the effects of witnessing violence on violent perpetration through increased attribution of hostile intent to a partner, generation of violence as a possible response, and belief in positive outcomes of violence.12
Attachment theory hypothesizes that witnessing intimate partner violence disrupts children’s attachment to parents, leading to emotional dysregulation, abandonment anxiety, and dependent attachment style in adulthood.5
Finally, researchers hypothesize that exposure to intimate partner violence can cause mental illness, including borderline personality organization, post-traumatic stress disorder, and antisocial personality disorder, leading to cognitive problems, emotional dysregulation, and high levels of anger.13
Research supports these causal pathways, indicating that boys who witness intimate partner violence are more likely to approve of violence, to believe that violence improves one’s reputation, and to justify their own violent behavior, compared with boys who have not witnessed such violence.14
Children exposed to intimate partner violence have high negative emotional reactivity, behavioral dysregulation, externalizing problems,15
and lower IQs16
than unexposed children. In turn, evidence from adults indicates that many of these factors relate to adult perpetration of intimate partner violence, as perpetrators are more likely to attribute hostile intent, to view violence as acceptable,17
and to have lower verbal and social skills and poorer marital communication than nonperpetrators.17,18
Studies also suggest that negative effects of witnessing violence may be mitigated with high levels of family emotional support. Emotional support in childhood may protect against future violence perpetration5
by buffering the negative effects of witnessing violence on internalizing and externalizing problems, substance use,19
personality, and violent behavior.20
However, this possible protective effect has not been specifically assessed for the relationship between witnessing intimate partner violence and perpetration of such violence.
Despite the empirical and conceptual bases supporting a causal relationship between intimate partner violence witnessing and perpetration, most past estimates adjust for few factors associated with witnessing that may also cause later perpetration. Therefore, published associations may not represent causal effects. Instead, the observed association may be explained by confounding factors—prior causes associated with both witnessing and perpetrating intimate partner violence. Potential confounding factors include parental criminality, mental illness, tendency to violence, antisocial personality disorder,10,21,22
alcohol and drug problems,21,23
and low socioeconomic status. 10,23
These parental traits and behaviors may increase both the risk of the child witnessing intimate partner violence and the risk of the child’s exposure to physical, sexual, and psychologic abuse,7,10,14,21
and community violence,20
experiences which may increase the likelihood that the child will perpetrate intimate partner violence in adulthood. Reviews of the literature have emphasized the need for more sophisticated methodologies to determine the independent effects of witnessing intimate partner violence and other potentially confounding childhood factors on later perpetration.13,14,23,24
Moreover, the validity of studies of the impact of witnessing intimate partner violence has further been questioned because many studies rely on shelter or clinic samples10,14,24
with small numbers of male perpetrators.10
Given this limited state of knowledge and the need to better estimate the causal impact of witnessing intimate partner violence in childhood on subsequent perpetration, we attempt to estimate the causal effect of witnessing such violence in childhood on perpetration in adulthood using propensity-score analysis. This approach has previously been used to examine the effect of exposure to community violence on gun-carrying and perpetration of community violence.25
Propensity-score analysis entails comparing perpetration outcomes between groups of men who have and have not witnessed intimate partner violence but who are otherwise comparable with respect to a wide range of potential confounders.
Propensity-score modeling is particularly useful in situations where the distribution of some confounders between those with and without the exposure of interest overlap only slightly. In these situations, estimates of causal effects from regression analyses are determined mostly by extrapolation, and the researcher may not be aware of the limited overlap in characteristics of the exposed and unexposed groups. Lack of overlapping characteristics threatens the assumption of exchangeability between the exposed and unexposed upon which causal inference rests. However, stratifying on the propensity to be exposed to the causal factor—in this case, witnessing intimate partner violence—before conducting regression analysis largely eliminates the problem of extrapolation. 26
Furthermore, if there are strata with no overlap between exposed and unexposed, propensity-score analysis may help researchers identify the subpopulation to which their estimates apply.27
To assess whether emotional support protect against the effects of witnessing intimate partner violence, we exclude emotional support from the propensity-score model and include it as a distinct variable in models of intimate partner violence perpetration.