Introduction

Interpersonal violence is a high-priority issue for the general public, policymakers, and academics. It is commonly defined as the use of physical force - threatened or actual - with the intent to cause harm or injury (Dahlberg & Krug, 2002), and can be contrasted with collective or political forms of violence. Its negative consequences range from immediate effects, such as personal harm and injury, to longer-term consequences for offenders, victims, bystanders, and the bereaved. Interpersonal violence also incurs major costs to society, especially via mental health services and criminal justice sanctions. Interpersonal violence is multifaceted, in its causes (adverse childhood experiences; personality traits; social inequality; risky behavior), but also in its effects (physical and mental ill health, trust in the government, resource distributions). Therefore, the topic of interpersonal violence has drawn the attention of scholars across different disciplines for some time now. These different perspectives reflect the fact that interpersonal violence is not only a crime, but also a breakdown of interpersonal relationships, a source of fear and insecurity, and a cause of physical and emotional harm, injury, and death (Dahlberg & Krug, 2002). As such, interpersonal violence is a relevant topic not only in the domain of criminology but also in public health, law, medicine, and psychology. Importantly, however, interdisciplinary integration between these various perspectives is lacking (see Hartmann, 2017). In this comment, we take up the question of how scholars and practitioners can work towards this aim of greater integration with other perspectives, to generate a more comprehensive understanding of interpersonal violence.

Interpersonal violence as an integrated, interdisciplinary research field

Currently, interpersonal violence is studied in the margin of other related phenomena. For instance, in criminology, interpersonal violence is studied as a form of crime. In public health, interpersonal violence is studied for its implications for health and quality of life. In each discipline then, there is a focus on specific elements of interpersonal violence. Relatedly, different disciplines tend to study different violence types. Gender scholars focus on—for instance—domestic and LHBTQ violence and femicide. In this work, the gender elements are central, while the violence aspects are peripheral—violence is of interest primarily because of what it tells us about gender relations and the experiences of disadvantaged groups. Similarly, developmental psychologists study interpersonal violence for its impact on developmental trajectories. Integration is needed to bring together these different perspectives into a comprehensive theoretical framework. In the study of political violence, interdisciplinary work has been responsible for considerable progress in the field. For instance, International Relations was developed as an interdisciplinary combination of history and law (Aalto, 2015). The study of interpersonal violence will benefit from similar initiatives. We believe that this endeavor will be helped by developing the study of Interpersonal Violence as a research field in its own right. Rather than creating a new distinction or replacing established disciplines, the establishment of this research domain should support synthesis in the study of interpersonal violence, by centering the concept of Interpersonal Violence.

In this comment, we report on an initiative that takes up the question of how scholars and practitioners in the field of interpersonal violence can work toward greater integration. The guiding question of our initiative is: If we want to move towards an integrated and interdisciplinary understanding of interpersonal violence, what concrete questions and challenges must be answered? To address this question, we brought together a group of interpersonal violence experts for a week-long workshop in June 2023. The group included key stakeholders, and academics from the fields of criminology, victimology, public health, psychiatry, sociology, psychology, and biology.

Overall, participants agreed that the fragmentation we see in the study of interpersonal violence is likely to be due—in part—to the fact that interpersonal violence is a complex and multifaceted phenomenon. As such, there is a critical need for nuance in our understanding of interpersonal violence. Interpersonal violence is not a unitary phenomenon, it has subtypes as diverse as assault, robbery, and rape, each of which has its own unique predictors and consequences. Several of these types may themselves have subtypes (see e.g., Tanskanen, 2021), and may be interpreted in different ways by those involved (Tutenges & Sandberg, 2023). The desire for nuance is not incompatible with our focus on integration. Integration on the one hand and nuance on the other will ensure a clearer view of where meaningful similarities occur and where meaningful differences lie, as opposed to focusing on differences created by conventions and interests of the disciplinary fields. To achieve integration without sacrificing contextual nuance, we identified five priority issues that call for attention in the study of interpersonal violence:

  1. 1.

    Theoretical development

  2. 2.

    The boundaries of “interpersonal violence”

  3. 3.

    Interpersonal violence in context

  4. 4.

    Global perspectives

  5. 5.

    Data quality in the study of interpersonal violence

Theoretical development

The first priority arising from the workshop is the need to build a stronger theory. Perhaps due to its fragmented nature, the field of interpersonal violence remains relatively theory-lean. Prominent theories of interpersonal violence often take the form of theories of other phenomena (e.g., crime—Akers & Jensen, 2017; aggression—Berkowitz, 1989; social control—Black, 1983) that are adapted to also apply to interpersonal violence. While this is not inherently problematic and can represent an important step in the process of theoretical development, in the case of interpersonal violence adapted theories are not adequate to explain interpersonal violence, and give a partial picture at best (Liem, 2022). On the other hand, there are several prominent theories that aim to explain specific types or elements of interpersonal violence (e.g., feminist theories of violence against women—McLeod et al., 2020; evolutionary theories—Wilson & Daly, 1985). To move forward with the study of interpersonal violence, it is necessary to examine the areas of agreement and contradiction between these theories. Further, more extensive empirical validation is needed to examine which theories are empirically supported in violence research. These steps will help the field move towards a more unified theory of interpersonal violence. By theoretical development we mean not only the development of new theories, but also the development of a more mature theory, which includes integration, re-formulation, and falsification in the case of deductive analysis (Ferguson & Heene, 2012; Frankenhuis et al., 2023).

Functional approaches to interpersonal violence seem—in our opinion—to be particularly promising. Functional approaches are those that consider interpersonal violence as a functional and potentially adaptive action in a given environmental incentive structure. There has been a recent resurgence in such approaches to interpersonal violence (see e.g., Fenneman et al., 2022), and this functional approach to interpersonal violence is also compatible with existing theoretical frameworks, where violence has been described as ‘self-help’ (Black, 1983), or ‘agency’ (Lindegaard & Jacques, 2014), or ‘violence capital’ (Eriksson et al., 2022). What remains to be done in this area, then, is to consider the relationship between violence that arises from functional dynamics and violence that arises from dysfunctional processes, such as among those with psychiatric illnesses. Indeed, the first step may lie in considering the fact that the functionality of an act is in part a perception on the part of those involved—while some violent behaviors might arise from dysregulated processes (such as those resulting from drug abuse or psychiatric conditions), the individual in question may perceive the act as a sensible and helpful response to a dangerous environment.

Macro-level causes of interpersonal violence also require greater theoretical attention, and particularly their integration with meso- and micro-level factors. Noted scholars recently lamented the failure to develop comprehensive theories of the geographic and temporal variation in cross-national violence rates (LaFree, 2021; Messner, 2021). Societal rates of interpersonal violence tell us something deeply elemental about culture and societal structure, but explanations of any changes to them remain underdeveloped. Moreover, violence is not only an outcome of social forces but is itself part of the social fabric. The prevailing characteristics of victims, offenders, and violent events thus likely follow systematic trajectories as societies develop. An example of theorizing that incorporates macro-level explanations for patterns of interpersonal violence alongside meso- and micro-level explanations can be found in the Criminologic Transition Model (Pridemore, 2024), which describes how the characteristics of violent events at the micro- and meso-level, and the nature of violence itself, change over time under the influence of the larger social fabric within which they occur.

The boundaries of interpersonal violence

The concept of interpersonal violence represents a continuum of harm from very extreme forms of violence such as homicide, to lower-level forms such as verbal threats and abuse. At the upper boundary, homicide has a special place in interpersonal violence research because of its relatively clear-cut outcome. As such, the study of homicide provides a unique opportunity for comparative research on violence across different contexts. It enables comparisons over long durations of time (Eisner, 2014; Gerring & Knutsen, 2022; Kivivuori et al., 2022), and across geographical space in the contemporary world (see, UNODC, 2023). However, the extent to which homicide can serve as an indicator of violence more generally is a matter of some debate (van Breen, Devarakonda, et al., 2023; van Breen, Rabolini, et al., 2023). The lower boundary of the violence continuum also poses serious, and interesting, challenges for interpersonal violence research. This is so because the lower boundary of what counts as interpersonal violence, is contested and culturally variable (De Haan, 2008; Lauwaert, 2019). Should rough talk and ‘microaggressions’ be included under the conceptual umbrella of violence? The fact that conceptual expansion has taken place, for example in intimate partner violence and cyber-aggression, seems to be beyond doubt (Gillespie, 2019; Yar & Drew, 2019). Why such trends exist is a more complex question. The ‘Durkheimian’ hypothesis suggests that the broadness of the violence concept reflects societal factors, such as trends in physical violence and the general affluence of societies (Durkheim, 1966; Kivivuori, 2014; Lynch & Addington, 2015; Moynihan, 1993): in contexts where rates of direct physical violence are low, this creates space for broader conceptualizations of harm, transgression and violence. In terms of how these changes occur, the label “violence” is evocative—it suggests behaviors that are unacceptable and harmful. As such, applying the label violence to a certain issue or behavior signals its unacceptability. This is illustrated in how modern political pressure groups often campaign for the expansion of the violence concept to include their focal issues (Boches & Cooney, 2022).

Some scholars have argued that expansions in the concept of violence are problematic because they undermine conceptual clarity and lead to “concept creep” (see e.g., Haslam, 2016; Roodt, 2019). Here we propose a different approach, namely that research on interpersonal violence should not take for granted any pre-defined lower boundary, or ‘campaign’ for the expansion or contraction of the violence concept. Rather, we suggest that the boundary of what is considered violent is a worthwhile topic for objective empirical research, and can generate relevant insight into the embeddedness of violence in broader societal trends and developments, such as (for instance) the rise of social media. Further, it can generate insight on differences between lay understandings of interpersonal violence, and how it is operationalized in law.

Violence in context

Interpersonal violence is embedded in a larger ‘web’ of complex interactions among causes and adverse outcomes in the social and health domains, underscoring the need for interdisciplinary approaches. For instance, those experiencing substance abuse, mental health challenges, and economic hardship may be more susceptible to violence, whether as victims or perpetrators (see also de Bles et al., 2019). In fact, correlation and comorbidity between different adverse outcomes is one of the central observations in the work of the early Sociologists (Durkheim, 1966; Quetelet, 2013)—and has a long and productive history in the field of criminology as well as sociology (Collins, 2009). While qualitative researchers consider contextuality almost by definition (see e.g., Korstjens & Moser, 2017), we see potential for developments in quantitative research on this point. In particular, there is a need for more structural evaluation of both shared and distinct causation factors. How do clusters of adverse outcomes come about? Are phenomena causally related? Or do their relationships come about because of a shared association with a third driving factor? In explaining the reasons for clusters of adverse phenomena, this research can build on a well-established theoretical framework of social deprivation in sociology and criminology (Shaw & McKay, 1942; Wilson, 1987), thereby promising to connect social approaches to violence, with health approaches to violence (e.g., van Breen & Liem, 2022). Identifying shared features of various adverse social problems may contribute to more impactful social policy, and as such this issue is also identified as a key priority by the stakeholders represented in our initiative. Second, in line with considering how different adverse outcomes cluster together, we might also apply similar reasoning to the side of the predictors. Importantly, in recent years there has been considerable development in syndemics approaches (Meyer et al., 2011) that can help to address these questions quantitatively. Syndemics occur when two or more epidemics come together in a specific population and interact in such a way that the prognosis and burden of disease are exacerbated. As such, the syndemics approach can help us conceptualize the relationship between violence and other phenomena (Mezzina et al., 2022). Also, the concept of cumulative burden in syndemics underscores how co-occurring health and social issues disproportionately affect marginalized and vulnerable groups (Quinn et al., 2023; Yang, 2023). Similarly, we can consider the benefits of a “complex systems” or “complexity science” approach (e.g., De Beurs et al., 2021; Scheffer et al., 2024). Such approaches have been gaining ground for instance in the field of Psychiatry (van der Wal et al., (2021)). Complexity science is related to syndemics approaches in the sense that both conceptualize the phenomenon under study as a system of complex interactions that do not necessarily have linear cause-and-effect relationships, but can also include feedback loops, cascade effects, and the like. With the development of such frameworks, we believe this is an opportune moment for the field to begin tackling the position of interpersonal violence within the broader network of adverse outcomes.

Global perspectives

The importance of sensitivity to context is also crucial in understanding global variation in violence. And here, too, we believe integrated and interdisciplinary approaches can facilitate such nuance. Rates of interpersonal violence vary widely across the globe. In Latin America for example violence can be seen as endemic (Escaño & Pridemore, 2023; Vilalta, 2020), whereas in Europe rates are much lower. Even within Europe, rates of interpersonal violence differ significantly between Western and Eastern Europe (Haagsma et al., 2022). Understanding global variation in violence requires high-quality comparative research, to examine how different patterns of violence might be explained, and to identify any shared underlying principles that can explain the different patterns across contexts. For instance, it has been shown that globalization is associated with a reduction in violence in poor countries, but effects are attenuated in affluent countries (LaFree & Jiang, 2023). Similarly, interventions that rely on income transfers as a way of preventing crime are likely to have a stronger impact on violence in locations like the United States or the Global South, while being less effective in European welfare state regimes based on continuous high-income redistribution (Rogers & Pridemore, 2013, 2017; Sariaslan et al., 2021). Practically speaking, there are several initiatives to establish databases that facilitate international comparison. The WHO Mortality Database tends to be the standard (Rogers & Pridemore, 2023), alongside this we see the development of initiatives such as the European Homicide Monitor (Kivivuori et al., 2024; Liem et al., 2013) that currently covers Sweden, Finland, the Netherlands, and Switzerland (with partial coverage in Denmark, Estonia, and France), is beginning to be implemented in the Caribbean, Indonesia, and South Africa; the instrument is thus potentially evolving towards a Global Homicide Monitor. Only by drawing on such instruments designed for research, can we explore whether the theories and explanatory frameworks apply globally. Crucially, we argue that to be able to go forward, the point of departure for comparative work should not by default be Western approaches. That is, comparative work should go beyond examining whether an effect demonstrated in the West applies in the Global South as well, but consider the Global South from the inception of a project (Zhang & Liu, 2023). One of the reasons why we see such a strong over-representation of Western perspectives when it comes to quantitative research in the domain of interpersonal violence relates to data quality and the lack of valid data from, for example, countries in the Global South. As such, it is relevant to note that expanding research on interpersonal violence to low-resource contexts is becoming more realistic through data collection by mobile phones or social media that can facilitate access to more diverse populations, including those in remote locations (Beres et al., 2022; Bogolyubova et al., 2020).

Data quality

High-quality methods play a key role in the interdisciplinary understanding of interpersonal violence. However, obtaining reliable quantitative data on violence has long been a “bottleneck” in the study of interpersonal violence. At the macro level, homicide data is relatively valid, at least in Western countries. Further, good-quality data on non-lethal interpersonal violence is often difficult to obtain, an issue that applies to all world regions (Nivette, 2021). As it stands, non-lethal interpersonal violence is difficult or impossible to study at the macro-level by administrative statistics. Fortunately, there are several positive developments in this area. Systems like the International Self-Report Delinquency Study (ISRD, see Marshall et al., 2022) go some way to capturing the unrecorded, hidden crimes through self-report, which is key to the study of interpersonal violence (Kivivuori, 2014). Second, efforts have been made to evaluate the implications of certain empirical conventions in the study of interpersonal violence(van Breen, Devarakonda, et al., 2023). Additionally, many databases now include survey indicators of violence that combine subjective experiences of violence with items asking about objective experiences, such as having received a physical injury, to ensure that cross-national comparisons are possible (see Nivette, 2021). Given the difficulty of collecting macro-level data on violence, many researchers prefer to rely on existing databases, such as those collected by the World Health Organization, or the UN Office on Drugs and Crime (UNODC). In this branch of research, a positive development is the increased scrutiny regarding the quality of data and measurement (Goes, 2023; Rogers & Pridemore, 2023). In terms of further development, we see a need for greater general awareness and uptake of best practices identified. For instance, researchers using cross-national surveys to compare data from different countries or cultural contexts should pay close attention to issues of measurement invariance to ensure that constructs can be compared (Wang et al., 2018).

At the micro-level, data quality is relatively poor as it regards the actual violent event. Interpersonal violence often takes place out of sight and hence can rarely be directly observed by researchers. Positive developments in addressing this, include the availability of novel tools and technological possibilities to collect data on violent events as they occur. Increasing surveillance of the public domain by CCTV cameras and the use of smartphones has increased the availability of video footage of violent events, which allows us to generate a frame-by-frame account of violent events (Philpot et al., 2019). Immersive technologies such as virtual reality provide recourse here as they allow for staging credible and immersive versions of violent events and studying in detail how people respond to them (see e.g., Slater et al., 2013). The increasing availability of registration-based data, and the development of more efficient algorithms resulted in a sharp increase in the application of machine learning to predict complex behavior such as suicide (Kirtley et al., 2022). Likewise, artificial intelligence will certainly shape the data landscape in years to come. These developments are not unique to the domain of interpersonal violence but given the sensitive nature of violence-related data, we believe these developments give rise to some unique challenges for our field. We urge caution particularly when it comes to the ethical implications of how such data are collected (c.f. collection of data through social media by tech companies; violent material being shared online).

The rise of collaborative science practices and Open Science (Chin et al., 2023; Pridemore et al., 2018) represents a third positive development when it comes to high-quality data and methods. Improvements needed in this domain—as above—center on greater uptake of these possibilities. Researchers studying interpersonal violence have been relatively slow in the uptake of Open Science initiatives. Although there are legitimate reasons for this (e.g., data on violence can be sensitive and therefore difficult to share), the Open Science initiative is broader than sharing data and also includes pre-registering study protocols, openly sharing code or other study materials, having independent agents within institutions replicate key analyses before publishing and using registered reports, including some that are specifically tailored to qualitative research (see e.g., Huma & Joyce, 2022; Karhulahti, 2022).

Ultimately, higher-quality quantitative data will facilitate interdisciplinary integration of findings. More robust data will reduce artificial fluctuations between studies and bring into sharper focus meaningful differences and nuances. Conversely, interdisciplinary integration will facilitate higher-quality data, from more diverse sources and with stronger methods.

Conclusion

The study of interpersonal violence has seen considerable growth over the last decades and now requires integration and consolidation. This has proven complex because the study of interpersonal violence is strongly contextual, which can sometimes be at odds with integration. As such, the field requires a form of interdisciplinary integration that can also respect nuance. We set out to identify challenges that must be tackled to make progress on this point. Over the course of the workshop, the 5 priorities we outline here reflect those areas where substantive consensus could be reached. By engaging with these 5 priorities, we will see progress toward a form of interdisciplinarity that works for the study of interpersonal violence—an integrated and complete understanding of a phenomenon that is known to be highly contextual. First, the field would benefit from the development of theories and approaches specific to interpersonal violence. Second, we believe it is necessary to consider cultural perceptions of what “counts” as violence, particularly its lower boundary. Third, we suggest more systematic attention to connections between violence and other adverse phenomena. Fourth, we argue for global perspectives on violence that can account for differences between global regions, while aiming for comparability. Finally, in light of “big data” initiatives and technological development, data quality is a point that requires careful attention over the years to come. The priorities we outline here are certainly not universal—different scholars and stakeholders will have their own aims and priorities. Still, we collectively argue that these issues are priorities if we seek to generate an integrated and interdisciplinary understanding of interpersonal violence. The issues we outline all speak to the need to balance integration, overarching patterns, and general principles, with nuance and contextuality. Interdisciplinary collaboration is needed to achieve these goals.