Military service and alcohol use: a systematic narrative review

Abstract Background Despite research highlighting the role of alcohol in military life, specifically in relation to mental health and certain combat experiences, there is no synthesised evidence looking at the relationship between military service and alcohol use. Aims To synthesize and examine evidence exploring the relationship between military service and alcohol use. Methods Six databases were examined across a 10-year period. Papers were included if they involved a military population and focused on alcohol use. From 4046 papers identified, 29 papers were included in the review. Results Military characteristics and experience were linked to high levels of alcohol use across military populations. Societal and cultural factors also played a role in alcohol use in military populations. Predatory behaviour of alcohol establishments, pressures to conform, an acceptance of alcohol use, and the role of religious services and military affiliated social networks were all considered. Excessive drinking impacted physical and mental health. Those diagnosed with PTSD and associated symptoms appeared to have greater alcohol use. Conclusions This review identified certain characteristics and experiences of military service that are associated with higher levels of alcohol use. It is important to identify risk factors for alcohol misuse to develop appropriate policy, targeting prevention.


Introduction
Alcohol has played a prevalent, historic role in military life, where, internationally, it has been used as a means of mediating stress, both in theatre and in the aftermath of battle [1]. Used in social bonding and comradeship [1], drinking has become a common and accepted behaviour in military culture, surpassing alcohol use in the general population [2,3]. Beliefs on acceptable drinking norms can be influenced and reinforced when exposed to the military social environment [4].
The Motivational Model of Alcohol Use indicates consumption of alcohol may be used to cope, and to 'regulate the quality of their emotional experience' [5 p. 990]. These reasons for alcohol misuse have also been evidenced in serving military and veteran populations [4]. However, regardless of the potential advantages of alcohol consumption socially, especially in enhancing positive emotional experiences, problems develop when alcohol is misused. For military service members, exposed to highly stressful situations, behaviour around long-term alcohol use can be affected by the accepted social norms around higher levels of alcohol use for recreation and coping [4].
Research has suggested that alcohol may serve as a coping mechanism after traumatic events, where deployment has been associated with increased rates of alcohol use or problem drinking [6]. Drinking to excess may have a negative impact on mental and physical health [7], functional impairment [8], troop readiness [9], suicidal ideation [10] and the perpetrator in military sexual assaults [11]. Furthermore, the UK Armed Forces have expressed concerns that 'excessive drinking can undermine operational effectiveness, leave soldiers unfit for duty, and damage trust and respect within the team' [12 p. 12].
Alcohol use and military service are of great importance and a public health issue. However, there are no systematic reviews of literature that focuses on the wider, overall experiences of alcohol use and military service. Existing systematic review evidence stresses the important role of alcohol in military life, particularly focussing on the comorbidity of PTSD and alcohol misuse [13], Gulf and Iraq/Afghanistan war veterans [14], or as part of systematic reviews with a wider mental health focus [15]. Therefore, this study employs a systematic narrative review that aims to explore the relationship between military service and alcohol use.

Methods
To appraise evidence from multiple sources including qualitative and quantitative research, and to ensure an inclusive systematic search without bias, a systematic narrative review strategy was employed [16]. Suitable databases were searched, identifying published peerreviewed evidence (Table 1).
Research papers on alcohol use with a military sample published prior to March 2021 were considered. Since the Global War on Terrorism began in 2001, there has been an increase in combat deployments of military service personnel from many nations across the globe. During this period, warfare has evolved, and the world has seen a more complex form of modern warfare, adapting and modernising to become more technologically advanced. This has also resulted in a change in the nature of deployments, impacting the role of military service in the lives of serving personnel. Deployments are dangerous and stressful for military personnel and combat stress, specifically experienced in Iraq and Afghanistan, has been associated with alcohol misuse [14]. Consequently, only papers published after 2001 have been considered in this review to ensure an accurate representation of the role military service has on alcohol misuse.
The exclusion criteria included papers that were unavailable in English, focussed on treatments or interventions for alcohol problems, or the sample included veterans. Papers on substance use were included, only if they reported alcohol use. The PICO framework was used to develop the search terms (Table 2). Truncation and wildcard search strategies were utilised.
Veterans and ex-service were included as search terms to ensure the maximum number of papers were returned. However, only papers with a serving military population were included in the review. The ex-service

Key learning points
What is already known about this subject • Historically alcohol has had an integral role in military life and has been seen as an acceptable behaviour in social bonding and comradeship. • Alcohol misuse in military populations has been associated with a negative impact on social, physical, and psychological health. • Literature reviews to date have focussed on comorbidity of PTSD and alcohol misuse, wider mental health and Gulf and Iraq/Afghanistan war veterans, no systematic reviews of literature have considered the wider experiences of alcohol use and military service.

What this study adds
• Military-specific traits and experiences such as, service type, rank and deployment status are linked to higher levels of alcohol use in military populations across multiple countries. • There appears to be an over-reliance on self-report questionnaires for the assessment of alcohol use in a military population focussing on symptom severity, with a paucity of research considering personal experiences and meanings ascribed to alcohol use. • The systematic narrative review has brought together a body of knowledge on alcohol use in a military population and the synthesis of this literature provides an evidence base to help inform future policy.
What impact this may have on practice, policy or procedure • There are specific characteristics strongly associated with military service that impact alcohol use, it is important to identify these 'risk factors' to mitigate the impact on operational effectiveness and workplace cohesion by developing appropriate and targeted prevention policies. • Mental ill health and harmful levels of alcohol use in military personnel co-exist and more specifically, this creates internal stigma making this population particularly reticent to seek help for both alcohol and mental health problems and therefore harder to identify. • The systematic narrative review has highlighted a lack of consistency in the tools and measures used to assess alcohol use in a military population and suggests a need for a consensus of assessment measures in practice and wider research.
military population was excluded because of additional, non-military specific, factors that exist that may impact alcohol use such as their experience of transition out of the military. Following the search of the databases, 4046 papers were returned ( Figure 1). A full-text search was carried out on 83 papers to determine the suitability for inclusion in the review. To appraise the quality of papers included in the review, the Critical Appraisal Skill Programme [17] tool was consulted. Fifty-four papers were excluded due to their focus on a veteran population or alcohol use not specific to military service. No further papers were identified through reference and citation searches. Consequently, 29 papers were included in this review.
Thematic analysis was used to analyse the papers and generate themes. The six steps of Braun and Clarke [18] were followed: familiarization with the data, generation of initial codes, searching for themes, reviewing themes, defining and naming themes, and producing the report.

Results
Twenty-nine papers were included in this review (Table  3). There were 22 studies represented across all 29 papers. Studies with multiple papers in this review included: the Health and Wellbeing of the UK Armed Forces Cohort Study [2,8,39]; Ohio National Guard (OHARNG) Mental Health Initiative [34,36]; Department of Defence Health Related Behaviours study [28,35] and the Prevalence, Incidence and Determinant of PTSD and Other Mental Disorders (PID-PTSD +3 ) study [40][41][42].
Four themes were identified in the literature: Military Characteristics and Alcohol Use, Consequences of Deployment on Alcohol Use, Implication of Mental Health on Alcohol Use and The Role of Cultural and Social Factors on Alcohol Use.
Fifteen papers considered military characteristics associated with alcohol use in their military samples [2, 19, 20, 22-25, 27, 29, 30, 33-35, 40, 41]. Hooper et al. [29] surveyed 1382 military personnel and reported they had a higher number of units of alcohol consumed per week than the suggested 'low risk' drinking threshold. In comparison to the general population, Fear, Iversen [2] identified a greater percentage of hazardous drinkers in a military population than in the general population.
Only two papers considered the potential differences in alcohol consumption between men and women. Fear et al. [2] suggested a gender difference in hazardous drinking where there were a greater number of male hazardous drinkers (67% military, 38% general population) than female hazardous drinkers (49% military, 16% general population). However Fadum et al. [24] noted that high alcohol consumption did not differ much between military women and men. Furthermore, no significant difference in high alcohol consumption between military and civilian women was found [24]. Papers in this review also considered the consequences of heavy drinking whilst serving in the military. For personnel that had deployed on operational service, a greater volume of drinking was linked to difficulties at home during and post-operational deployment [19,41]. In addition to demonstrating a high incidence of alcohol use in the military, the papers reported evidence of associations between alcohol use and factors such as age, service type, active deployment, combat exposure, mental health, and relationship status. In UK, US and German military populations, heavy drinking has been associated with holding a lower rank, being younger, being single, being in the Naval service or Army, being deployed to Iraq, not having children, being a smoker, having a combat role and having a parent with a drink or drug problem [2,19,23,25,35,41]. Most papers examined such risk factors in soldiers from US or UK military populations, potentially providing limited applicability to military populations in developing nations [22]. Interestingly, in contrast to US and UK findings, Cheng et al. [22] identified older age rather than younger age as a significant risk factor for alcohol use in Angola.
Literature suggests that, in the UK, levels of drinking are higher in the Army than other branches of the military [2]. Different subcultures of drinking within individual branches have been attributed to these variations across the military, especially under circumstances that involve personnel taking part in team activities where there may be pressure from peers to drink alcohol to relax and debrief [2]. These situations that involve socialising and alcohol use are a common feature of Armed Forces life and particularly in the Royal Navy. In this regard, Henderson, Langston [27] reported significant degrees of harmful drinking among personnel serving in the Royal Navy in comparison to the civilian population.  Browne et al. [19] To explore the association between heavy drinking and military deployment factors Campbell-Sills et al. [20] To identify prospective risk factors for postdeployment heavy drinking and alcohol or substance misuse disorder To explore the role of civilian stressors on alcohol use disorders Quantitative 2616 US N/S National Guard Cheng et al. [22] To examine alcohol consumption patterns and related risk and protective factors In addition to heavy and hazardous drinking, substantial levels of binge drinking have also been found in military populations across UK, US, German, Angolan and Nigerian military populations [2,20,22,25,30,33,40]. Binge drinking in the UK, has been associated with being younger, being in the Army, being single and being a smoker [2]. Furthermore, there appears to be a difference in the prevalence of binge drinking between Active Duty/Regular soldiers and National Guard/Reserves. Larson, Adams [33] identified that there was a marked difference between those personnel in Active Duty who reported frequent binge patterns of alcohol use than those in the National Guard/Reserves.
Rates of alcohol use have been perceived as the highest for those with combat specific jobs or those with a greater number and higher intensity deployments [6].
Furthermore, despite Special Operations Forces experiencing greater exposure to combat deployments than conventional forces, Dretsch et al. [23] determined that the prevalence of alcohol misuse in 16 284 Special Operations Forces soldiers was comparable or lower than reported by the wider military. This paper had the largest sample of the papers included in this review.
Research has indicated that heavy alcohol use often occurs during pre-and post-deployment with a significant association to the deployment period itself [6,20,30,37,43]. Most of the research primarily focuses on personnel with military service during the Iraq War Adverse combat experiences during deployment have been associated with heavy drinking in military personnel [19,21,38]. Hooper et al [29] discussed how the active involvement in theatre of war had strong links to problematic drinking habits among serving personnel who feared for their own mortality and who 'experienced hostility from civilians'. Wilk, Bliese [44] also found that soldiers who had higher rates of exposure to the threat  [44] To examine the association of specific types of combat experiences with a positive screen for alcohol misuse  of death or injury were significantly more likely to screen positive for alcohol misuse. Exposure to atrocities similarly predicted misuse of alcohol with alcohol-related behavioural problems. Although in Russell [37] all combat experiences were also positively correlated, only the combat experience of killing was significantly related to post-deployment alcohol use. Interestingly, alcohol use decreased amongst those who experienced killing during combat. The authors' explanation for this was based on the suggestion that the 'killing experience may activate the soldiers' mortality salience and trigger a self-preservation focus that manifests itself in reduced risky alcohol consumption' [37]. No other paper in the review considered this.
Alongside the available evidence that suggests that fighting the enemy in battle and witnessing the horrors of war predisposes serving personnel to the risk of problematic alcohol use, Skipper et al. [38] suggested that serving personnel who are part of 'special forces' are at an even higher risk of providing a positive alcohol test result due to problematic drinking if they are involved in hostile warfare. In line with adverse combat experiences, Browne, et al. [19] also argued that personnel who deployed with their parent unit, whose role in theatre was outside, above or below their training or experience and who experienced poor in-theatre unit leadership were more likely to be heavy drinkers.
Despite several papers in this review (n = 13) identifying a significant link between deployment and subsequent alcohol use, regardless of country, Thandi et al. [39] demonstrated that levels of drinking were not related to deployment status. Marshall et al. [34] also found no effect of deployment on alcohol use, although this was for those who reported pre-deployment depression or PTSD. Three German papers support the suggestion that deployment has no effect on alcohol use [40][41][42]. Interestingly, the correlates of increased average daily alcohol use across two time points in these papers, were limited social support, greater sleeping difficulties and increased negative post-event cognitions following deployment [41]. Lower PTSD symptom severity pre-deployment and less childhood emotional neglect, predicted a decrease in average daily alcohol consumption [41]. It is possible to suggest that specific deployment experiences impact alcohol use in a military population rather than deployment in general. However, these German papers were all from the same Prevalence, Incidence and Determinant of PTSD and Other Mental Disorders (PID-PTSD +3 ) study. Additionally, Orr et al. [36] identified that only pre-deployment preparedness was associated with incident alcohol misuse when controlling for demographics, deployment related factors (e.g. exposure to warzone stressors), and the presence of psychopathology.
US research has identified further differences within a military population. Around 13-14% of National Guard/ Reserve personnel exhibited high levels of drinking in association with deployment [31,33]. Whereas Larson et al. [33] discovered that an increase in alcohol use as a result of deployment was actually greater in Active-Duty personnel compared to the National Guard/Reserves. Regardless, alcohol use following deployment is thought to be uniquely predicted by higher levels of PTSD symptom severity, higher levels of avoidance-specific PTSD symptoms and lower levels of positive emotionality [31]. It is worth noting that although there appears to be an indication of differences in alcohol use with engagement type following deployment, more research is needed to further explore this.
Although not a focus of this review, eight papers focussing on alcohol use in a military population reported on the implication of mental health [8,25,28,31,32,34,39,40]. This included five papers looking at the role and impact of PTSD [25,31,32,34,39], one on wider mental health [40], one on suicide [28] and one on functional impairment [8].
Previous research has suggested military personnel with PTSD may use alcohol for self-medication as a coping mechanism for distress related to psychological symptoms [31,34]. Five papers indicated a significant association between PTSD symptom severity, heavy drinking behaviours and new-onset Alcohol Use Disorder [25,31,32,34,39]. However, once the influence of personality variables were accounted for, Ferrier-Auerbach et al. [25] found that mental ill health was not associated with any drinking variable.
Although baseline PTSD symptoms significantly increased the risk of screening positive for new onset alcohol dependence, Kline et al. [32] identified no effect of pre-deployment alcohol use on subsequent PTSD diagnoses post-deployment. Such findings indicate that it is possible that the specific psychological consequence of military deployment (e.g. PTSD) significantly impacts military personnel's alcohol use rather than being in the military in general.
In support of the specific psychological impact of deployment on military personnel's alcohol use, further differences have been identified between deployed and non-deployed military personnel. Trautmann et al. [40] identified among recently deployed soldiers, that heavy drinking was related to a higher risk of anxiety, affective and sleep disorders. Among soldiers never deployed, heavy drinking was linked with any mental disorders other than substance use disorder and was further associated with somatoform disorders. For those recently deployed, associations between heavy drinking and the presence of any mental disorder as well as anxiety disorders were significantly greater than those that had never deployed.
Beyond PTSD, Herberman et al. [28] identified that US soldiers who reported high levels of alcohol use were more likely to have seriously considered and/or attempted suicide. After adjusting for level of alcohol use, PTSD, and depression, drinking to avoid rejection/'fit in' was associated with suicidality.
One paper considered the impact of alcohol use on functional impairment. Rona et al. [8] identified that a score on the Alcohol Use Disorder Identification Test (AUDIT) denoting potential alcohol dependence was consistently associated with functional impairment, whereas binge drinking was not. Interestingly, despite a known impairment, participants with hazardous drinking perceived their functioning to be better than those with lower AUDIT scores. The implications of this perception should be explored further. Furthermore, half of the participants presenting with potential alcohol dependence also had psychological comorbidities.
Five papers identified the role of social support and communities in the alcohol consumption of military personnel [6,22,26,30,39]. The communities within which military personnel reside can have a prominent role in their alcohol use. Besse et al. [6] conducted interviews and focus groups with 29 US Active-Duty soldiers to understand the context of alcohol establishments in communities near military installations in relation to alcohol use. Participants identified predatory behaviour by local alcohol establishments to encourage excessive drinking, placing the profit as a higher priority over the safety of the soldiers. Free or reduced admission fees and drink specials were often specifically designed with soldiers in mind, with some participants reporting that alcohol establishments gave soldiers 'heavier pours' or mixed drinks with a higher proportion of alcohol. These findings indicate that there is a perception that military personnel drink more, thus increasing the availability of alcohol and subsequent use.
Unsurprisingly, Besse et al. [6] also ascertained that drinking has been described as an accepted way to relax and cope with stress brought on by the daily stressors of military life. Drinking alcohol was perceived to be an accepted part of military culture. Pressure to engage in heavy drinking often came from peers as an obligation to prove oneself to the group. This was particularly common among young military personnel or those new to a unit. Socialising appears to play a role in military personnel's alcohol use. Besse et al. [6] conducted the only qualitative paper in this review. The findings allow further insight into the reciprocal relationship between alcohol and military personnel by using interviews and focus groups to explore the reasons behind the relationship. Qualitative methods are highly appropriate for this paper, where the purpose was to learn how military personnel experiences the community within which they reside.
Unexpectedly, Cheng et al. [22] indicated that socialising with family and friends two to four times, but not five or more times, per month increased the risk for problematic drinking in military personnel. More specifically, Thandi et al. [39] identified that entering into a new relationship resulted in a decrease in alcohol use.
Only two papers considered the role of religion in alcohol consumption [22,30]. Cheng et al. [22] ascertained that attending religious services more than once a week appeared to protect against problematic drinking in Angolan soldiers. It is possible that the effect of religion on alcohol consumption is dependent on the soldiers' culture as another paper determined that religion had no role in drinking in Nigerian soldiers [30].
The social networks of military members appear to be crucial in the likelihood of alcohol use. For Reserve and National Guard soldiers, one paper indicated that drinking-related social network characteristics such as drinking buddies were associated with increased alcohol problems [26]. However, for those deployed, militaryaffiliated social networks were a protective factor against alcohol problems [26].

Discussion
This systematic narrative review explored the relationship between military service and alcohol use. From the 29 papers examined in this review, it is evident that there are military-specific traits and experiences which impact alcohol use, namely military characteristics, such as service type and rank, and military deployment. Mental health, cultural and social factors also play a role in alcohol use in a military population.
Throughout this review, there are associations drawn between military characteristics and alcohol use such as service type, rank and deployment status [2,19,23,25,35,41], that have been associated with higher levels of alcohol consumption in military populations in a number of countries [2,20,22,25,30,33,40]. Additionally, studies have pointed towards a difference between alcohol use in a military population and the civilian population [2,27]. Although, Fadum et al. [24] indicated no difference between military women and civilian women.
Most papers indicated that alcohol use was greatest in those with deployment experience, especially those with adverse combat experiences [6,19,21,38]. This is unsurprising, at least in a UK military population, where policy allows the continuation of alcohol use during military 'decompression', where those returning from combat receive a short duration of absence together with psychological support [45]. There was a suggestion that these findings were a result of using alcohol as a coping mechanism after traumatic events, however, further work is needed to explore this. Specific combat experiences were significantly related to screening positive for alcohol misuse for elite and non-elite military personnel including personal threats, fighting and atrocities [38]. Interestingly, an increase in alcohol use following deployment was greater for Active-Duty personnel compared to the National Guard and Reserves in a US cohort [33]. It is important to note that not all research found a significant link between deployment and subsequent alcohol use, regardless of country, a few papers argued that deployment had no effect on alcohol use in military populations [34,[39][40][41][42].
Evidence in this review suggests that mental ill health and harmful levels of alcohol use in military personnel co-exist. But, more importantly, the evidence suggests that internal stigma makes this population particularly reticent to seek help for both alcohol and mental health problems. Kiernan et al. [46] identified that many veterans only present for help when they can no longer cope with the situation, they find themselves in. This study found that seeking help for alcohol misuse issues late, when problems have escalated significantly, invariably led to a co-morbid presentation, a significant decline in mental health and excessive drinking, usually exacerbated by a collapse of the individuals social support network. Once more, this strengthens existing evidence that excess drinking negatively affects physical, social, and mental health [7,46]. Specifically, PTSD symptom severity was significantly associated with greater alcohol use [25,31,32,34,39]. Heavy drinking was also related to a higher risk of anxiety, affective and sleep disorders, functional impairment, and suicide [8,28,40].
This review also suggests that culture and social factors can influence alcohol use in a military population. An interdependent relationship was identified between military personnel and local alcohol establishments near military installations [6]. It was suggested that establishments tailor their business, often in a predatory way that is perceived as detrimental to military personnel's health, well-being, and career. The behaviour of alcohol establishments near military installations was felt to exacerbate this alcohol acceptance. However, only one US paper considered this, more international research should be conducted to consider if this is a common experience in a military population. Interestingly, there was a suggestion that attending religious services [22] and that having military affiliated social networks when deployed [26], protected against problematic drinking.
Drinking alcohol was noted as an accepted way to relax and cope with stress in the military with some feeling pressure to conform to drinking [6]. This acceptance of alcohol use and the social norms surrounding its use can have life-long, post-military service implications, as military veterans who normalise or excuse their drinking, delay their engagement in substance misuse services [46]. The historic social and cultural norms within the military [1], and even the 'romanticising' of this culture [12] are now being recognised, and the UK's Ministry of Defence is trying to combat and encourage a sensible approach to alcohol use with initiatives to identify individuals' alcohol use during regular oral examinations [47].
In almost all studies considered for this review, the Alcohol Use Disorder Identification Test (AUDIT) or the modified brief version, AUDIT-C was utilised. The AUDIT and AUDIT-C have been acknowledged as valid instruments for identifying alcohol misuse or dependence among US and Australian military populations [48,49]. However, the validity of such tests in other military populations does not appear to have been completed, despite the variability in populations. Regardless of the validity of such instruments, research has relied heavily on self-report questionnaires for assessment in a Military population. This can result in ascertaining large volumes of data; however, this can also give rise to participants answering in a more socially desirable way, rendering results inaccurate [50].
This focus on quantitative research methods has made it difficult to draw any conclusions as to what the resulting impact of military service on alcohol use may have on the ability of service personnel to carry out their jobs. To mitigate this, future research must also consider a qualitative approach, considering personal experiences and meanings ascribed to alcohol use, rather than only symptom severity, to draw any conclusions.
This review has synthesised findings from existing literature, highlighting potential gaps in current research. Despite being a comprehensive, international systematic narrative literature review, it is important to acknowledge there are limitations. First, only papers written in English were considered for review and may have excluded inclusion of international findings. Only the relationship between military service and alcohol use of serving personnel was considered, with papers including veterans in their sample being excluded as it was outside of the aims of this review. Finally, only peer-reviewed research was included in this review and, whilst this was a purposeful decision, it is acknowledged that evidence from grey literature may illuminate further understanding of this issue.
This systematic narrative review aimed to critically evaluate existing literature to explore the relationship between military service and alcohol use. Findings indicated that there are specific characteristics strongly associated with military service that appear to have an impact on alcohol use. The subsequent effects of alcohol use in a military occupational context reinforces the validity of exploring the casual links in more depth. Further research is needed to identify specific 'risk factors' associated with serving in the military and problematic alcohol consumption. Exploring the attributable burden will be a crucial building block to developing appropriate and targeted prevention policies.