Navigating Dual-Harm: Integrating Self- and Other-Harm Into Public Health Inquiry

Abstract

Dual-harm, the co-occurrence of self- and other-harm, recognizes the overlap between these outcomes of aggressive behavior and their potential shared causes. Little progress has been made in preventing and responding to dual-harm in the broader population, and it remains understudied in public health research.

We posit that the scientific investigation of dual-harm would greatly benefit from the application of public health principles and methods. In this essay, we operationalize dual-harm as a public health problem and identify gaps in knowledge, addressing its conceptual and definitional issues, prevalence estimates, methodological considerations, theoretical foundations, risk factors, and prevention strategies. We also offer a series of recommendations to advance dual-harm study and challenge the notion of conflating nonfatal dual-harm with homicide-suicide as part of a continuum, arguing that they are distinct phenomena. We identify the need for epidemiological studies to characterize those engaging in dual-harm and better understand their mechanisms and outcomes, focusing on adolescence as a critical developmental period.

Future studies should develop, implement, and evaluate targeted intervention and preventive efforts for individuals involved in or at risk for dual-harm. (Am J Public Health. 2025;115(4):596–604. https://doi.org/10.2105/AJPH.2024.307940)

Self- and other-harm, outcomes of inward-outward aggression, are typically studied in isolation from one another, treated as separate phenomena, or even seen as opposite. Consequently, individuals who engage in either self- or other-harm are often considered to be 2 discrete populations. However, it is documented that some individuals engage in both.^1,2 This means that self- and other-harm may co-occur or be intertwined. Those involved in dual-harm may share a significant number of etiological pathways and risk factors but also present an exacerbation of such risks.³ Individuals engaging in dual-harm may share an underlying vulnerability to emotional and behavioral dysregulation that drives aggression while facing long-term life difficulties.⁴ Framing self- and other-harm as nonlinked fails to examine the directionality and possible feedback loops between them and overlooks the associated risks. For example, a population-based case–control cohort study found that individuals engaging in dual-harm had a higher risk of death from external causes and a greater prevalence of multiple drug misuse than those with either no history of harm or single-harm involvement.⁵

A significant number of dual-harm studies have been conducted in clinical and forensic settings (e.g., with prisoners and forensic inpatients), focusing on high-risk populations.^1,2 Nonfatal dual-harm incidents that take place in nonclinical settings are equally challenging, and it is important to better understand them; to date, however, there has been limited data or research informing this phenomenon. Only a small proportion of those who harm themselves attend or receive clinical services; that is, most self-harm episodes occur at the community level (i.e., non-high-risk samples, such as adolescents from the general population).⁶ Official records provide little insight into aggression among those without contact with the criminal justice system. Additionally, there is very limited research that has framed nonfatal dual-harm via a population-based approach. Incidence and prevalence rates in the general population, as well as their distribution among subgroups, remain unexplored, and longitudinal harm trajectories (i.e., no-harm vs single-harm vs dual-harm) have been barely explored.⁷

For these reasons, we advocate for incorporating the study of dual-harm into the public health research agenda. Decker et al.’s integrated public health approach to interpersonal violence and suicide prevention provides a strong foundation for nonfatal dual-harm prevention, grounded in an intersectional and socioecological framework.⁸ Recent research has begun to explore the prevalence, trajectories, and risk factors associated with dual-harm, primarily at the individual level. However, there remains a gap in addressing risk patterns of inward-outward aggression through a multilayered perspective that considers age, gender, sexual orientation, and race/ethnicity. Also lacking is a population-level approach that incorporates social determinants of health, including structural factors (e.g., urban policies like redlining) and community factors (e.g., hazardous conditions, neighborhood collective efficacy) and their impact on dual-harm prevention.⁹ Such an approach would help shape an epidemiological characterization of the population that engages in dual-harm, leading to a better understanding of its correlates, pathways, and outcomes, as well as the role of oppression, inequality, and power dynamics. Ultimately, this would allow for the prevention of dual-harm by distinguishing the variables and patterns linked to dual-harm from those associated with single- or no-harm and facilitate the early detection of those involved in dual-harm. This is crucial because self-harm emerges during late childhood and early adolescence,¹⁰ a period when various changes in the patterns and levels of antisocial and criminal behavior also occur and intensify.¹¹

In this essay, we review the theoretical and empirical foundations of dual-harm research, and highlight key research in this area to date, gaps in the existing knowledge base, methods of prevention, and suggestions to move new studies forward. We also offer a series of reflections to increase awareness and help further expand public health research and inquiry.

DUAL-HARM: CONCEPTUAL AND DEFINITIONAL ISSUES

The variability in the study on both self- and other-harm is also reflected in the study of dual-harm, referred to as the co-occurrence of self- and other-harm. There is currently no agreed-upon operational definition of dual-harm, which is particularly challenging because of the convergence and exacerbation of issues present in both self- and other-harm literature. We therefore discuss 5 main elements of contention in dual-harm research:

• 1.the definition of self-harm,
• 2.other-harm—the specific aggressive behaviors relevant to the dual-harm construct,
• 3.the role of homicide followed by suicide with dual-harm research,
• 4.the behavioral time span, and
• 5.the identification of the harm groups.

Self-Harm

Self-harm refers to nonfatal acts of self-poisoning or self-injury.¹² Yet, there remains an ongoing debate on the definition, boundaries, and taxonomy of self-harm behaviors. Some describe self-harm as occurring regardless of suicidal intent, whereas others define it in the absence of such intent, irrespective of the motivation or degree of suicidal intent.^6,13 This has led to a loose definition of self-harm since, depending on the frame, it can encompass nonsuicidal self-injury (NSSI), indirect self-injury, or a suicide attempt. Presently, 3 leading organizations have addressed the definitional issues. The American Psychiatric Association differentiates between NSSI (self-inflicted damage to the body surface or internal injury) and self-harm with intent to die (i.e., suicide attempt). The Centers for Disease Control and Prevention (CDC) distinguishes suicidal self-directed violence from nonsuicidal self-directed violence; in both cases, behaviors deliberately cause injury, but in nonsuicidal self-directed violence, there is no explicit or implicit suicidal intent (i.e., no fully revealed or expressed intention either implied or inherent in the nature of something, as defined by the CDC).¹⁴ The International Society for the Study of Self-Injury defines NSSI as an intentional or expected self-inflicted injury resulting in immediate physical injury not intended to cause death or based on social or cultural practices,¹⁵ thus delineating NSSI from thoughts or behaviors with suicidal intention. Lack of specificity or uncertainty exists across definitions regarding the required body damage or the level of immediacy of the resulting injury. Consequently, some studies differentiate between NSSI and suicide attempts when considering self-harm, whereas others do not.

From a practical standpoint, to address suicidal-related behaviors, public health scholars can rely on the conceptualization provided by the International Study of Definitions of English-Language Terms for Suicidal Behaviors (ISDELTSB).¹⁶ It offers a minimum starting consensus covering the views of high-income and low- to middle-income countries. As the ISDELTSB suggested, self-harm involves nonfatal self-inflicted harm where the intent to die is either absent or not observable. If the person reports intent to die, the suicide attempt is the preferred construct. Therefore, a suicide attempt involves self-inflicted harm with intent to die in which the person survives.

Other-Harm

The most accepted definition of human aggression is a goal-directed behavior aimed at causing harm to another person who wants to avoid the harm.¹⁷ Aggression encompasses various modalities, subtypes, motivations, and behavioral patterns, whereas the severity of acts varies widely across its forms. Dual-harm research has utilized either a broad or narrow range of aggressive behaviors toward others, depending on the specific focus of the study. Some have considered multiple forms of aggression, and others focus solely on physical aggression, excluding verbal aggression or property damage. However, the question of which behaviors are pertinent—and why—remains open to interpretation.

Reaching a certain degree of consensus on the aggressive behaviors relevant to dual-harm will be a lengthy process. Although some variability according to context is expected, it would be helpful to outline the core of the phenomena and delve into why self- and other-harm are associated with one another. To advance this early-stage field, we suggest that researchers prioritize interpersonal aggression, adopting a relatively narrow approach to establish a solid foundation. We suggest focusing on direct aggression (behaviors openly aimed at causing physical or psychological harm to others or coercing them¹⁸) and relational aggression (a nonphysical form of aggression aimed at damaging or threatening to damage relationships¹⁸). In particular, we emphasize moderate and severe forms of direct physical aggression, which include sexual aggression.

We also consider relational aggression in intimate relationships to be a significant component of dual-harm, although its consistent measurement remains challenging because of several methodological issues associated with relational aggression measures.¹⁹ We recommend including it only if it is assessed adequately.

In contrast, alongside noninterpersonal aggression, we suggest excluding the relational aggression modality of bullying from the core set of behaviors, for several reasons. Although a meta-analytic review has found a relationship between bullying perpetration and dating violence perpetration,²⁰ the link is weak, largely based on cross-sectional research, and does not account for the relative contributions of bullying subtypes. Bullying is particularly rooted in peer dynamics and group processes, which can encourage bystander involvement, especially in its mild to moderate forms.²¹

An exploratory, data-driven examination of additional behaviors that may expand the dual-harm construct can complement the proposed core set of behaviors. Shafti et al. made an initial attempt to analyze the relationship between self-harm and various types of aggressive behaviors, finding a weak correlation.²² They concluded that relational aggression, in the forms of bullying and dating violence, should not be included in their definition of dual-harm. Notably, the study assessed bullying and dating violence differently, categorizing both as relational aggression but capturing only physical instances of dating violence, which conflicts with the definition of relational aggression applied in aggression research. We urge researchers to properly capture and describe aggressive behaviors. Additionally, certain types of violence, such as bias-based violence, are uniquely shaped by sex/gender, race/ethnicity, disability, and other intersecting identities, highlighting the need to consider how some forms of violence manifest.^23,24

Lessons From Homicide-Suicide Literature

Akin to the dimensional model of suicide, it has been suggested that dual-harm can be understood as a continuum based on the level of harm, with homicide-suicide representing its most serious form.² Most research on homicide-suicide and nonfatal dual-harm has been conducted independently. Theories addressing dual-harm have arisen from the suicide and extreme aggression framework, whereas less severe forms have received less theoretical attention.^1,2,25 Homicide-suicide presents several conceptual challenges, including the lack of a formal or legal definition, questions about whether it should be limited to intentional homicides, and variability in the time frame of occurrence (typically within 24 hours, but sometimes extending to days, weeks, or without a specific limit).^25,26 Homicide-suicide is an extremely rare event that primarily occurs within the family context.²⁷ Internationally, the incidences vary around the world, ranging from 0.05 to 0.89 per 100 000 inhabitants.²⁵ We argue that homicide-suicide may be better understood as a distinct phenomenon from nonfatal dual-harm and that it may constitute distinguishable subpopulations. Even when one considers self- and other-harm in high-risk populations framed within the broader conceptualization of dual-harm, homicide-suicide is regarded somewhat separately.²⁸ Research in homicide-suicide is framed in death studies, mass murder, femicide, familicide, terrorism, lethal firearm use, or copycat crimes.^26,29 Including homicide-suicide as part of the dual-harm continuum—the hypothesis of escalation—may potentially blur the discussion by considering an outlier with different sociodemographic characteristics, contextual factors, and situational inducement.

Time Span

Another key definitional element with no consensus is the time span in which self- and other-harm must occur to qualify as a dual-harm incident. The emergence of dual-harm among youths is likely to follow a developmental sequence.³⁰ Individuals typically begin with 1 behavior and transition later to another, as they may serve different functions.^31,32 Dual-harm has been measured either concurrently or sequentially. The 2 systematic reviews covering any form of dual-harm have employed a broad approach to time frames (i.e., lifetime).^1,2 Longitudinal data can help to identify dual-harm progression and to what extent it is sensitive to a specific developmental period, such as adolescence. We suggest that if the assessment is longitudinal, the 12-month window is a usual measure in many cohort studies, allowing one to gather information accurately while reducing recall bias.

Harm Groups

Once the behaviors are identified, cross-tabulation allows for the identification of individuals who engage in harmful behaviors and classify them into the following groups: self-harm, other-harm, and dual-harm. The dual-harm group can be further disaggregated into 2 groups to assess directionality (self-harm to other-harm and other-harm to self-harm) if the study design allows for adequate assessment of the temporal order of events. Similarly, the single-harm group can also be disaggregated between those who engaged in self-harm or other-harm.

PREVALENCE ESTIMATES

Dual-harm prevalence varies according to the narrowness of the definition used, the population studied, and the measures employed: 0.9% of people incarcerated (89.1% no-harm),³³ 11% in a prospective sample of psychiatric inpatients,³⁴ 13% in a cohort of psychiatric outpatients,³⁵ 2.8% of adults (aged ≥ 18 years),³⁶ 0.4% in a population-based cohort of adolescents (14.8% within the self-harm group),⁴ 3.7% of youths in a intergenerational cohort study,³⁷ 4.7% in a cohort of youth twin pairs,³⁸ 7.2% in a stratified random cohort of adolescents,³⁹ and 17.1% in another prospective population-based cohort.⁴⁰ As observed, there is a wide range of prevalence across studies. Interestingly, the prevalence is surprisingly low in the largest study so far involving incarcerated persons,³³ which defies current dual-harm knowledge²⁸ and the well-known elevated risk of mortality, morbidity, and behavioral problems among this population.⁴¹ These findings warrant further research.

METHODOLOGICAL CONSIDERATIONS

Most dual-harm investigations heavily rely on cross-sectional designs and relatively small sample sizes.^1,2 Only a handful of cohort studies have started to address the longitudinal course of self-, other-, and dual-harm together.^5,7,33,38,39 Because of definitional and methodological heterogeneity and the implications of the types of measures used (e.g., self-reports or psychophysiological measures), making direct comparisons across studies is challenging. A common approach to nonfatal dual-harm studies is the use of nonvalidated self-report measures to assess harmful behaviors.² We suggest using validated measures of aggression and cross-informants’ perspectives to capture children’s and adolescents’ behaviors while being aware of the limitations of identifying causal effects.^42,43

Level of Analysis

Traditional clinical and epidemiological research is nomothetic (population-based, focused on interindividual variation). Nomothetic knowledge is fundamental, but understanding aggressive behaviors also requires an idiographic (individual-based, focused on intraindividual variation) approach. At the societal level, researchers can address societal factors by examining policies and policing practices, such as health care accessibility, (de)criminalization, income security, crisis support resources, and school-based mental health programs. To assess the influence of cultural norms and beliefs, researchers can use large social or public opinion surveys. This can be combined with individual-level data to examine how broader societal or environmental factors interact with individual characteristics influencing aggressive behaviors and associated outcomes, although it requires data harmonization.⁴⁴ At the group level, nomothetic analysis identifies population patterns by examining differences between groups, the primary approach for advancing dual-harm research at this early stage. It helps uncover what differentiates those engaged in dual-harm from those involved in single- or no-harm. Here, researchers can follow our suggestion to find a balance between conceptualization and measurement and how to leverage the existing public health data. At the individual level, idiographic approaches using clinical data can provide insights for more personalized treatment by helping to understand the dynamics underlying mental health issues, identifying the optimal timing for intervention, and uncovering unique symptoms or individual differences that contribute to the outcome.⁴⁵ Time series analysis or real-time evaluation, such as ecological momentary assessment, can be a fruitful methodology to capture processes influencing behaviors.

Data Sources

To study human aggression, public health researchers often use a variety of data sources intended for different purposes, such as hospital records, nationally representative surveys via existing surveillance systems, and crime and criminal justice data. These different types of data sources pose different shortcomings. For instance, public health survey data collecting self-harm and suicide exhibit greater variability across data collection levels, procedures, and case classification while relying on self-reports and not capturing fatal instances. Similarly, health care data also underrepresent instances of self-harm, in particular nonfatal attempts. They focus on injuries and immediate medical outcomes but, unlike crime data, often lack a broader psychosocial context. Medical records can also contain stigmatizing language that drives implicit bias.⁴⁶ Because of its design, International Classification of Diseases (ICD) coding has limitations as a tool for determining intentionality and perpetrator relationships. On the other hand, crime and criminal justice data are based on legal definitions that often differ across jurisdictions and from the scientific consensus.⁴⁷ Some crimes are not necessarily intended, as incidents can escalate, or the result can be somewhat accidental. The wording can be narrow but inaccurate, overinclusive, or encompassing a broad range of behaviors that vary in severity (e.g., domestic violence).

We suggest that public health researchers employ multiple sources of data not limited to observational accounts and capitalize on nationally representative data sets to epidemiologically characterize the population of those involved in dual-harm and provide more reliable estimates of its incidence and prevalence in the community. Useful references for this endeavor include a review of national data sources on adolescent suicidal ideation and suicide attempts, including related factors such as aggressive behaviors,⁴⁸ as well as a systematic review of ICD-10 codes for all forms of injury.⁴⁹ For example, the National Violent Death Reporting System can be used to study homicide-suicide, but also premature or accidental death related to nonfatal dual-harm.

Public health researchers must carefully examine both self- and other-harm and be transparent about the pros and cons of the selected approach to provide evidence to build the scaffolding for a reliable conceptualization of the behaviors and outcomes that are relevant to the dual-harm construct. That said, there are no gold standard measures for all scenarios to capture self- and other-harm and the related risk factors and outcomes. The use of objective and subjective measures has advantages and disadvantages that need to be considered.^50,51 Otherwise, researchers may overlook potential measurement bias. For instance, common method variance can occur in cross-sectional studies when the same method and source are used to capture the variables of interest, such as the relationship between a psychological construct and behavior, leading to potentially detrimental effects (e.g., inflated correlations).

THEORETICAL CONSIDERATIONS

Because of the conceptual problems and limited research, it is still not possible to ascertain whether dual-harm is a separate behavioral construct from self- and other-harm with distinct, unique underlying factors. Current evidence suggests that dual-harm may represent an overlap between self- and other-harm, along with their associated factors, with the exacerbated effect potentially leading to dual-harm.² Reflecting a similar foundational idea, the Two-Stage Model of Countervailing Forces⁵² posits that there is an innate aggressive impulse that underlies both self- and other-harm, with its expression dependent on the interaction of psychosocial variables that either amplify or attenuate the impulse (Stage I), whereas a second set of variables determines whether the aggression is directed inward toward the self or outward toward others (Stage II). It should be noted that Stage II does not conclusively distinguish chronic trait vulnerabilities for co-occurring self- and other-harm from acute state factors determining the aggression direction (i.e., inward-outward).¹ To offer a model specifically designed for dual-harm, the Cognitive-Emotional Model of Dual-Harm builds upon previous work rooted in the General Aggression Model, emotion regulation, and diathesis-stress models.⁵³ The model underscores the prospective distal, proximal, and feedback mechanisms involved in dual-harm, as well as the influence of personality style and the potential emotional regulation and interpersonal purposes. As the authors acknowledge,² the model represents the first, albeit not an exhaustive, attempt to provide scaffolding for further theoretical developments and empirical tests. For instance, the model does not elaborate on emotional regulation intricacies nor address other functions of self-harm apart from those related to self-regulation purposes.⁵⁰ It does not explain what distinguishes dual-harm from other behavioral outcomes or include distal biological factors.⁵³

RISK FACTORS

Developmentally, numerous risk factors contribute to self- and other-harm. Nevertheless, the factors’ relative contributions vary among individuals. This heterogeneity can be interpreted by means of equifinality (the same variables can lead to different outcomes) and multifinality (different variables can lead to the same outcome).⁵⁴ Individuals engaging in dual-harm differ by their cumulative increased risk compared with those involved in no- or single-harm.² The reciprocal dynamics in the development of self- and other-harm can be addressed using the developmental cascade framework.⁵⁵ This metaphor posits that difficulties in 1 area can trigger a chain reaction, spreading problems across interconnected domains over time through transactional processes. These effects increase vulnerability and change trajectories, with early risk factors initiating ripple effects across domains that amplify over time.

Plutchik reported at least 23 shared risk factors for self- and other-harm.⁵² Since then, research has further enhanced our understanding of the potential risk factors relevant to dual-harm.^1,56 These include early life adversity, impulsivity, sensation seeking, poor coping skills, mental health problems (e.g., substance misuse, substance use disorders, aggressive-related disorders), cruelty to animals, environmental and genetic factors, and alterations in neurochemistry,^{5,38,39,57,58} such as serotonergic (5-HT) dysfunction, which has been associated with reduced cerebrospinal fluid 5-hydroxyindoleacetic acid (CSF 5-HIAA) levels.^59,60 By contrast, research on protective factors and resilience is still minimal. Differences between men and women among those engaging in dual-harm are barely explored, although it has been suggested that they may be less pronounced compared with those involved in single-harm.³⁹ Additionally, they might follow different transitions from the dual-harm to single-harm groups, with women more likely to transition to the self-harm group and men to the other-harm group.⁷

Findings across life course epidemiology, developmental psychopathology, and life course criminology have highlighted that childhood and adolescence are critical periods for a myriad of later outcomes, whereas antisocial, risky, and criminal behavior peak in the late teens, and early starters represent a high-risk group.¹¹ Enhancing the study of self-harm during this life period is crucial. Likewise, emphasizing the study of prospective longitudinal research is the only reliable path to improve our understanding dual-harm, its causes, and its trajectories. Along with the need for further theoretical development of dual-harm, models of self- and other-harm can generate hypotheses suitable for investigating risk factors and correlates of dual-harm.

PREVENTION

Special attention should be given to the prevention of dual-harm in youths from a socioecological perspective. Thus, efforts must not be limited to individual and interpersonal factors alone at the individual level. Emphasis on social and structural factors such as poverty, sexism, genderism, racism, ableism, and access to health care and education needs to be addressed⁶¹ while deploying interventions at the community level according to the characteristics of settings such as neighborhoods or schools.⁶² The aforementioned Cognitive-Emotional Model of Dual-Harm provides a good opportunity to start building prevention strategies specifically focused on individuals involved in dual-harm at the primary, secondary, and tertiary levels.⁵³ Primary prevention can encompass the implementation of educational programs or community outreach grounded in theory, as well as policy endeavors promoting healthy coping strategies, substance misuse awareness, and programs for educational achievement.^63,64 Secondary prevention can deploy screening programs and training for early detection, provide counseling and mental services, and offer cognitive and self-regulatory interventions to target maladaptive thoughts and behaviors.^63,64 Tertiary prevention can establish rehabilitation and support services, therapeutic approaches to reduce relapse and withdrawal—such as continuous monitoring and follow-up to detect early signs of recurrence—and intensive case management for individuals with chronic and severe aggressive behaviors.⁵⁶

CONCLUSION

To summarize, this essay reviews the conceptual, definitional, and methodological challenges of dual-harm research, along with its theoretical basis, risk factors, and prevention strategies. Box 1 summarizes the issues and gaps, and our suggestions to advance research. We recommend following the emerging consensus on defining self-harm within the context of suicidal behaviors. We propose outlining the core aggressive behaviors relevant to the dual-harm construct before proceeding to avoid an overly inclusive or inconsistent set of behaviors that could hinder comparability and replication. Additionally, we posit that nonfatal dual-harm and homicide-suicide are distinct phenomena with different underpinnings and risk factors and should not be considered part of the same continuum. Rather, it would be beneficial to clearly distinguish homicide-suicide, an extremely rare event, from nonfatal dual-harm. However, comparative research between the two remains valuable. We also suggest the need to epidemiologically characterize the population of those who engage in nonfatal dual-harm, explore its subgroups, and shed light on the social determinants of health associated with it.^65,66

BOX 1—

Issues and Gaps in Dual-Harm Research and Suggested Recommendations

Issues and Gaps	Recommendations for Future Research
Definition of self-harm	Self-harm: A nonfatal intentional self-inflicted harm covering different motives in which the intent to die is either absent or not observable. If intent to die is captured, use suicide attempt. Suicide attempt: An act in which a person harms themselves, intending to die, and survives.
Aggressive behaviors relevant to dual-harm	Focus on interpersonal aggression, specifically prioritizing moderate and severe forms of direct physical and sexual aggression. Include relational aggression in intimate relationships only if it is measured accurately.
Homicide-suicide as the most extreme form of dual-harm	Homicide-suicide is better understood as a distinct phenomenon from nonfatal dual-harm because of its uniqueness and different underlying factors rather than as part of a dual-harm continuum.
Methodological	Use validated measures of aggression and cross-informant perspectives. Level of analysis: Population health and combined individual- and population-level approaches are needed. Community and structural social determinants of health, like policy and environment, remain largely unexplored, along with intersectional approaches to age, gender, sexual orientation, and race/ethnicity. Data sources: Utilize diverse data sources beyond observational accounts and leveraging representative data sets.

We urge public health researchers to tackle this important topic and be mindful of existing issues and limitations. Researchers should aim for consistency in both the conceptualization and measurement. This will enable a progression from the current dichotomous view toward a more nuanced understanding, allowing comparisons of the extent and severity of behaviors within the dual-harm population. Late childhood and adolescence warrant special attention as key stages for the development of dual-harm. Future studies should contribute to developing tailored interventions and preventive measures for those engaging in or at risk for dual-harm.