Summary of the Study on Norwegian Veterans’ Mental Health and Combat Killing Contexts

Core Findings:

• Contextual Influence: The psychological impact of killing in combat is heavily influenced by the mission’s context. Soldiers in combat-oriented missions (Afghanistan) experienced no long-term mental health harm from killing, whereas those in peacekeeping missions (Lebanon) showed higher rates of PTSD, depression, anxiety, and reduced quality of life.
• Mission Expectations Matter: When killing aligns with pre-established group norms and mission rules (e.g., clear combat roles in Afghanistan), it does not inherently cause moral injury. Conversely, in peacekeeping contexts (Lebanon), where lethal force contradicts mission goals, it leads to psychological distress.
• Group Norms and Preparation: Soldiers mentally prepared for combat, with training and clear rules of engagement, are less likely to suffer adverse effects. Peacekeepers, unprepared for lethal encounters, face moral conflict violating their mission’s ethos.

Study Details:

• Sample: Analyzed 14,658 Norwegian veterans—10,605 from Lebanon (1978–1998) and 4,053 from Afghanistan (2001–2011).
• Mental Health Metrics: Assessed PTSD, depression, anxiety, insomnia, alcohol use, and quality of life.
• Key Variable: Killing in combat (KIC) was a significant predictor of negative outcomes only in peacekeepers, even after controlling for other traumas (e.g., personal threats, witnessing injury/death).

Theoretical Implications:

• Challenges the assumption that killing universally causes psychological harm, emphasizing the role of societal and mission-specific norms.
• Supports evolutionary psychology perspectives: Humans adapt to group-sanctioned violence when aligned with perceived “rightness” of actions.

Practical Implications:

• Military Policy: Ensure mission guidelines and rules of engagement are explicit, culturally understood, and reinforced through training.
• Veteran Support: Tailor mental health interventions to consider mission context. Combat veterans may require different support than peacekeepers.
• Societal Responsibility: Public and institutional recognition of soldiers’ actions within their operational framework to reduce stigma and moral conflict.

Limitations and Considerations:

• Cultural Specificity: Findings from Norway may not generalize to all militaries.
• Temporal Factors: Lebanon missions occurred earlier, potentially affecting recall or societal reintegration processes.
• Sample Size of Killers: Small subset of veterans who killed, though statistical significance was achieved.

Conclusion:
The study underscores that psychological outcomes of combat killing are not inherent but shaped by mission context, preparation, and alignment with group norms. This insight calls for nuanced approaches in military planning and veteran care, recognizing that moral injury arises from violated expectations, not the act of killing itself.

I. Executive Summary

A recent comprehensive study involving over 14,000 Norwegian veterans has yielded significant insights into the psychological consequences of taking a life in combat. The findings challenge the long-held assumption that such an act invariably leads to long-term mental health issues for soldiers. Instead, the research reveals that the context in which the killing occurs is the critical determinant of psychological outcomes. Specifically, veterans who served in Afghanistan, where combat was an expected aspect of the mission and the rules of engagement were clearly defined, exhibited no long-term psychological harm as a result of killing. Conversely, veterans who participated in peacekeeping operations in Lebanon and had killed someone were more prone to experiencing depression, post-traumatic stress disorder (PTSD), and a diminished quality of life. This disparity underscores the vital role of alignment between mission expectations, group norms, and the act of killing in shaping the psychological well-being of military personnel. These findings have profound implications for understanding combat trauma and for developing more effective strategies for military mental health support and pre-deployment training, tailored to the specific demands and contexts of different types of military operations.

II. Introduction: Challenging Prevailing Understandings of Combat Trauma

Historically, there has been a strong presumption that killing in combat is an inherently traumatic experience, inevitably leading to negative mental health consequences for those who perpetrate it ¹. This perspective is partly rooted in societal moral codes that generally condemn the taking of human life. Theories, such as those popularized by David Grossman in “On Killing,” have posited a deep-seated, innate aversion to killing among humans, suggesting that overcoming this aversion in combat comes at a significant psychological cost ². This widespread belief in society often assumes that taking another person’s life is fundamentally contrary to human nature and will invariably inflict psychological harm ¹.

However, the findings of the recent Norwegian study offer a compelling counter-narrative, suggesting that the act of killing in combat does not automatically equate to psychological damage ¹. The study’s key contribution lies in highlighting the crucial role of context in determining the long-term mental health impact on soldiers who have killed. By comparing veterans from two distinct operational environments—Afghanistan and Lebanon—the research demonstrates that the psychological outcomes are significantly different, contingent upon the specific circumstances of the mission, the expectations placed upon the soldiers, and the prevailing group norms surrounding the use of lethal force ¹. This novel perspective necessitates a re-evaluation of traditional understandings of combat trauma and calls for a more nuanced approach to supporting the mental health of military veterans.

III. Detailed Findings of the Norwegian Veteran Study: Afghanistan vs. Lebanon

The Norwegian study adopted a comprehensive methodology, examining the mental health of over 14,000 veterans who had served in either Lebanon (10,605 veterans who served between 1978 and 1998) or Afghanistan (4,053 veterans who served between 2001 and 2011) ¹. Researchers, including Andreas Espetvedt Nordstrand, Professor Leif Edward Ottesen Kennair, war veteran Ronny Kristoffersen, and former chief psychiatrist of the Norwegian Armed Forces, Jon Reichelt, identified those veterans within each group who had taken a life in combat ¹. The study then investigated how their experiences during their service had subsequently affected their mental health, focusing on a range of variables including PTSD, depression, insomnia, anxiety, alcohol consumption, and overall quality of life ¹. The large sample size, encompassing all Norwegian veterans from these missions, lends considerable weight to the study’s findings, suggesting a robust representation of the psychological impact within these specific operational contexts.

The findings for the Afghanistan veterans were particularly striking. The study revealed that for this group, taking a life in combat had no discernible long-term negative impact on their mental well-being across any of the investigated variables ¹. No trend of increased mental health problems, alcohol consumption, or reduced quality of life was identified among the Afghanistan veterans who had killed, even after accounting for other potential trauma exposures ¹. This suggests that within the context of the Afghanistan mission, where combat was anticipated and the use of lethal force was likely perceived as a necessary and justified aspect of their role, the act of killing did not serve as a primary driver of enduring psychological distress.

In stark contrast, the findings for the Lebanon peacekeeping veterans presented a very different picture. For this group, killing in combat emerged as a significant factor associated with subsequent mental health problems ¹. Veterans who had killed someone during their peacekeeping service in Lebanon were significantly more likely to experience depression, PTSD, increased alcohol consumption, and a reduced quality of life later in their lives ¹. The researchers emphasized the “huge” difference in mental health outcomes between the veterans from the two missions, highlighting the critical influence of the operational context on the psychological consequences of killing.

To further illustrate the contrasting outcomes, the following table summarizes the key findings of the study:

Table 1: Comparison of Mental Health Outcomes Between Afghanistan and Lebanon Veterans Who Killed in Combat

This table clearly demonstrates the divergent psychological impact of killing in combat depending on the mission context, underscoring the central argument of the Norwegian study that context, rather than the act itself, is the crucial determinant.

IV. The Critical Role of Mission Context and Expectations

The significant difference in psychological outcomes between the Afghanistan and Lebanon veterans can be largely attributed to the fundamentally different natures of their respective missions ¹. In Afghanistan, the operational environment was characterized by expected combat engagements with more aggressive adversaries ¹. Soldiers deployed to Afghanistan were likely prepared for the high probability of encountering hostile situations where the use of lethal force might be necessary for self-defense or the accomplishment of their mission objectives. This expectation, coupled with the inherent dangers of the mission, likely shaped the soldiers’ mindset and their understanding of their role.

Conversely, the mission in Lebanon was primarily a peacekeeping operation, focused on de-escalating tensions and maintaining peace ¹. While the risk of combat was present, it was considerably lower and less anticipated compared to Afghanistan ¹. Andreas Espetvedt Nordstrand noted that participating in a peacekeeping operation appears to make soldiers considerably more vulnerable to the psychological aftermath of killing another person than involvement in combat missions ¹. This vulnerability likely stems from the disparity between the mission’s overarching goal of preserving peace and the act of taking a life. The expectations of the soldiers deployed to Lebanon were likely centered on maintaining neutrality and avoiding conflict, potentially leading to greater internal conflict and moral distress when they were compelled to use lethal force. The study suggests that it is primarily the violation of group norms and mission guidelines that renders actions like killing psychologically harmful ¹. When the mission entails a high risk of enemy aggression, there is a greater degree of acceptance and leeway for the use of lethal force ¹.

V. Influence of Group Norms and Rules of Engagement

In the context of the Afghanistan mission, the expectation of combat and the likely clarity of the rules of engagement likely fostered group norms where the use of lethal force, when deemed necessary, was considered justified and aligned with the mission’s objectives ¹. According to Nordstrand, these group norms collectively shape what soldiers perceive as right or wrong in their operational environment ¹. When soldiers understand and experience that killing is an acceptable action when the situation demands it, such experiences are less likely to result in long-term psychological problems ¹. This suggests that a shared understanding within the unit, supported by clear guidelines, can act as a buffer against the potential moral conflict associated with taking a life in combat.

However, in the Lebanon peacekeeping context, the act of killing may have been perceived as a deviation from the expected norms of a peacekeeping mission, where the emphasis is typically on non-lethal engagement and the maintenance of neutrality ¹. Soldiers often exercise considerable caution to ensure their actions adhere to established group norms, particularly when those actions, such as taking a life, are far removed from the norms of civilian society ¹. The potential for a perceived violation of these peacekeeping norms when a soldier is required to kill could contribute to feelings of moral incongruence and the higher rates of mental health problems observed among the Lebanon veterans.

Rules of engagement (ROE) play a crucial role in defining the circumstances under which military forces can initiate and continue combat ⁴. In Afghanistan, the ROE were likely aligned with the combat mission, providing a framework for justifying the use of lethal force against hostile actors ⁵. This clarity may have helped soldiers to rationalize their actions within the accepted parameters of the mission. In contrast, the ROE for the peacekeeping mission in Lebanon might have been more restrictive, reflecting the mission’s primary objective of maintaining peace and minimizing the use of force ⁷. In such a context, the decision to use lethal force, even in self-defense, could have been perceived as a more significant moral transgression, potentially contributing to greater psychological distress. Further research into the specific ROE governing the Norwegian contingents in both Afghanistan and Lebanon could provide valuable insights into how these guidelines influenced the soldiers’ perceptions and subsequent mental health.

VI. Moral Injury: A Deeper Look at the Peacekeeping Context

The concept of moral injury offers a valuable lens through which to understand the distress experienced by the Lebanon peacekeeping veterans ⁹. Moral injury refers to the psychological, social, and spiritual impact of events involving betrayal or transgression of one’s own deeply held moral beliefs and values occurring in high-stakes situations ¹⁰. It can arise from perpetrating, failing to prevent, or witnessing acts that violate these moral principles, leading to feelings of guilt, shame, anger, and betrayal ¹². While moral injury can co-occur with PTSD, it is considered a distinct phenomenon ⁹. PTSD often stems from fear-inducing events, whereas moral injury arises from a sense of moral transgression ¹⁴.

Peacekeeping operations, by their very nature, can expose military personnel to situations that may lead to moral injury ³. The often-limited mandates and resources in peacekeeping missions can place soldiers in morally challenging positions, where they may be unable to intervene in situations of violence or injustice, leading to feelings of helplessness or complicity ¹⁶. The restrictive rules of engagement typically associated with peacekeeping, designed to minimize the use of force, could paradoxically increase the risk of moral injury when peacekeepers are unexpectedly compelled to kill ³. In such instances, the act of taking a life might be perceived as a profound violation of their moral code, particularly if their training and mission briefing emphasized de-escalation and non-violent conflict resolution.

Furthermore, moral injury can also result from a sense of betrayal by leadership or peers ¹³. It is conceivable that the Lebanon veterans might have experienced a sense of betrayal if the reality of their mission involved lethal combat despite being framed as a peacekeeping operation with an emphasis on non-violence ¹⁷. Exploring the specific experiences of the Lebanon veterans could reveal whether feelings of betrayal or a perceived lack of support contributed to their mental health challenges.

VII. Comparison with Existing Literature on Combat Trauma

The Norwegian study’s findings directly challenge the previously held notion that taking a life in combat is automatically detrimental to mental health ¹. While numerous studies have indeed demonstrated an association between killing in combat and negative mental health outcomes, such as PTSD, among veterans from various conflicts ², the Norwegian research highlights the critical importance of differentiating between combat roles and mission contexts. This suggests that broad generalizations about the psychological impact of killing might need to be refined to account for the specific circumstances of deployment.

Cross-cultural research on combat trauma also supports the idea that responses to traumatic events are influenced by cultural context and moral norms ¹⁸. Some studies suggest that certain symptoms of PTSD may be linked to culturally specific violations of moral norms ¹⁸. The Norwegian study’s emphasis on group norms aligns with this broader understanding, indicating that the interpretation and psychological processing of killing in combat are shaped by the social and military norms prevalent within the specific operational environment.

The role of unit cohesion in mitigating the negative psychological effects of combat has been well-documented ²⁰. High levels of unit cohesion are generally associated with improved morale and psychological resilience ²⁰. While unit cohesion can act as a buffer against stress, its interaction with traumatic exposure is complex, and its protective effects may vary depending on the level and type of stress experienced ²¹. It would be valuable to explore whether the levels of unit cohesion differed between the Afghanistan and Lebanon contingents in the Norwegian study and how this might have influenced the relationship between killing and mental health outcomes. Stronger unit cohesion in the Afghanistan context might have provided a more robust support system and shared understanding, further mitigating negative effects, while potentially being less effective in the morally ambiguous context of the Lebanon mission.

VIII. Implications for Military Mental Health and Veteran Support

The findings of this study have significant implications for military mental health policies, pre-deployment training, and the development of support programs for veterans. There is a clear need for pre-deployment training that emphasizes the specific rules of engagement, expectations, and mission guidelines relevant to the deployment context ¹. Mental health preparation should be tailored to the anticipated demands of the mission ²³. For peacekeeping operations, this might include specific training on navigating moral dilemmas and the potential for unexpected violence ²⁵. For combat missions, it is crucial to clearly and repeatedly articulate the mission’s objectives and the potential necessity of using lethal force in certain situations ²⁷. Military organizations should proactively manage expectations to align with the likely realities on the ground, potentially mitigating negative psychological consequences for soldiers.

Post-deployment mental health screening and assessment should incorporate measures to identify veterans who may have experienced potentially morally injurious events, particularly those who served in peacekeeping roles ²⁹. Tools such as the Moral Injury Events Scale (MIES) can be valuable in these assessments ²⁹. It is important to recognize that moral injury may manifest with symptoms that differ from those of traditional PTSD ⁹. Military and veteran mental health services should consider routine screening for moral injury to identify at-risk individuals and provide timely, tailored support.

The development of targeted mental health support programs is essential to address the specific challenges faced by veterans from different mission types ³⁰. For peacekeeping veterans, programs focusing on moral repair, self-forgiveness, and processing moral incongruence may be particularly beneficial ³². For combat veterans, support that reinforces the justification for their actions within the context of the mission and group norms could be helpful. Peer support groups, where veterans with similar experiences can connect and share their challenges, also hold significant potential ³⁴. A nuanced approach to veteran mental health support, acknowledging the contextual factors influencing the psychological impact of killing in combat, is crucial for improving outcomes.

Efforts to destigmatize mental health care within the military culture must continue ³⁵. Emphasizing that seeking help is a sign of strength and resilience is vital ³⁷. Service members need to be consistently informed about available mental health resources and assured that seeking support will not negatively impact their careers ³⁹. Overcoming the reluctance to seek help is fundamental to ensuring that all veterans receive the care they need, regardless of their mission experiences.

IX. Conclusion: Context Matters in Understanding the Psychological Impact of Killing

The Norwegian study provides compelling evidence that the psychological impact of killing in combat is not a universal phenomenon but is significantly shaped by the context of the military mission. The stark contrast in outcomes between Afghanistan veterans, who experienced no long-term psychological harm from killing, and Lebanon peacekeeping veterans, who were more likely to suffer from depression, PTSD, and reduced quality of life, underscores the critical roles of mission expectations, group norms, and the potential for moral injury. These findings challenge traditional assumptions about the automatic psychological damage associated with taking a life in combat and highlight the need for a more nuanced and context-sensitive approach to understanding and supporting the mental well-being of military veterans.

Further research could explore the specific rules of engagement and levels of unit cohesion in different mission contexts to gain a deeper understanding of their influence on psychological outcomes. Longitudinal studies tracking the long-term mental health of veterans from various deployments would also be invaluable. Ultimately, recognizing and addressing the contextual factors that shape the psychological impact of killing in combat is essential for developing more effective military policies, pre-deployment training strategies, and tailored mental health support programs that meet the diverse needs of our service members and veterans.