Introduction

Gambling disorder ([GD]; formerly labeled pathological gambling [PG]) is a debilitating mental illness characterized by persistent patterns of dysregulated gambling behaviors that negatively affect life domains such as social relationships, personal well-being, financial well-being, employment, and legal issues [1]. Importantly, beyond diagnosable GD itself, gambling behaviors may also be problematic without meeting full criteria for a diagnosis of GD. Subthreshold GD has been described by the terms “problem gambling” or “at-risk gambling” (e.g., 2-3 inclusionary criteria for GD).

The estimated lifetime prevalence of PG/GD among US adults ranges from 0.4 to 1.6% [2,3,4] and between 1.0 and 4.0% for problem gambling [5, 6]. A growing body of research has established that many factors are associated with greater risk of PG/GD, including younger age, male gender, US military service history, racial and/or ethnic minority status, lower education level, pre-existing mental health and substance use disorders, and delinquency/illegal acts [7,8,9,10,11].

For the current study, we use the term “veteran” to describe US adults who are “a person who served in the active military, naval, or air service and who was discharged or released under conditions other than dishonorable” [12]. Available estimates place the lifetime rates of GD in US military veterans around 2.0%, while the lifetime rates of problem gambling (clinical subthreshold) are as high as 9.0% [13, 14••, 15].

Research has also found that GD is associated with increased risk of obesity [16], stress [17], alcohol abuse/dependence [18], mood and anxiety disorders [19••], and personality disorders [20]. Among individuals with GD, researchers have found higher rates of psychiatric disorders [21], particularly among those with co-morbid GD and alcohol use disorders [22]. For instance, GD is associated with greater odds of experiencing incidents of negative mood, anxiety, or substance use disorders three years later [23]. Gambling frequently co-occurs with symptoms of post-traumatic stress disorder (PTSD) [24]. Traumatic experiences have also been found to predict problems with gambling in the future [25]. Individuals with both GD and PTSD are often highly distressed, more prone to suicidality [26], and high-utilizers of mental health treatment services [27]. Among treatment-seeking US Department of Veterans Affairs (VA) patients diagnosed with GD, research has also revealed high co-occurrences of substance use disorders and PTSD [10, 28].

Despite the many negative health and social outcomes associated with GD, only a small minority of individuals with GD (including subthreshold problem gambling) seek professional help for problem gambling [29]. Only an estimated 11% of individuals with GD will ever seek professional help in their lifetime [7, 30, 31]. This small number is particularly striking given that rates of natural recovery are low, with only a third of individuals with PG recovering naturally without professional intervention [31]. Among individuals who reached natural recovery, median time of recovery was 19 years. [32], suggesting that problem gamblers often suffer for nearly two decades before getting better. The reticence to obtain treatment for GD may be even stronger in active military members, who often state concerns about the confidentiality of their information and how such information could negatively impact their employment within the US armed forces [33].

Despite recent works highlighting the increased risk for GD among US veterans, particularly those with trauma histories [28], this population remains largely understudied. The purpose of this article is to review study findings on GD (including subthreshold problem gambling) in US military veterans and to highlight present concerns for this high-risk population. Recently, Section 733 of Public Law 115-232 H.R.5515 John S. McCain National Defense Authorization Act for Fiscal Year 2019 was passed by the US Congress requiring the Department of Defense (DOD) to “incorporate medical screening questions specific to gambling disorder into the annual Periodic Health Assessments of members of the Armed Forces” [34]. This legislation also requires the DOD to include questions about GD in their research using the Health-Related Behaviors Survey with active-duty personnel and reservists. Although research has found that gambling is associated with both family and personal problems for international veterans from the UK [35], overall there are few studies investigating the impact of GD on international samples of military veterans. As such, for this systematic review, we chose to include only studies using samples comprised of US military veterans/active-duty personnel. Specifically, we will examine the published literature on the rates, correlates, comorbidities, treatment, and genetic contributions to US veterans’ gambling behaviors. The intended results from this review are to help inform US federal policies specific to the identification and treatment of GD among military populations and will mainly focus on US military veterans.

Methods

Search Strategy

Protocols and strategies used in this systematic review were in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We first queried electronic databases (Medline/PubMed and PsycINFO) for peer-reviewed journal articles published between January 1, 1994 and November 23, 2019. PsycINFO covers 2290 journals and Medline/PubMed have a combined search of 5200 worldwide journals in over 40 languages. These dates were selected to obtain up-to-date information of GD in US military veterans while retaining relevant earlier studies of GD in military populations. The following key words were employed in this search: (gambl* AND military) OR (gambl* AND veteran). The study selection and screening process of identified studies is described in Fig. 1. Reference lists of included articles were checked manually for additional relevant publications.

Fig. 1
figure 1

PRISMA flow diagram of the systematic review phases

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Inclusion Criteria and Review Process

Articles were excluded if they were in languages other than English; they were a meta-analysis or systematic review; they were not peer-reviewed journal sources; the participants were adolescents or children; if the study used non-human participants; if the study did not include US veteran populations; and lastly, if the study was deemed to not be relevant to GD in veteran populations. Studies on the psychological and intellectual profile of veterans with GD were also excluded but have been discussed in a previous review [36]. The resulting full-text copies of all articles considered relevant to GD (including subthreshold GD) in US military veteran populations were retrieved and screened. Author RE reviewed all abstracts, and subsequently for the full text review, all authors collaborated to come to a consensus on the articles included in the final review. Three additional articles were found after the full text review, by searching article references and these were included in the final review, which encompassed 39 articles in total which are described below (see Table 1 for a summary of article categories).

Table 1 Summary of article categories
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Description of Studies and Measures Reported in Reviewed Studies

The articles covered in this review are typically cross-sectional studies with high proportions of white, male veterans. GD (or in some cases, “at-risk/problem gambling” which was defined by endorsing at least one GD symptom on a brief screening measure) was identified by a variety of measures, with the most popular measures described below. The South Oaks Gambling Screen (SOGS) [37] was the most commonly used measure for assessing gambling behavior and severity.

The SOGS [37] is a well-validated and reliable 20-item screener used to assess gambling severity (both GD and problem gambling) and maps on well to GD diagnosis criteria in the third, fourth, and fifth editions of the Diagnostic and Statistical Manual for Mental Disorders (DSM). A score of 5 or more is indicative of GD or “probable GD” and a score of 3–4 is considered to represent an at-risk/problem gambler. Furthermore, several studies assessed GD by use of diagnostic interviews (clinician-administered semi-structured or structured clinical interviews) or direct questions about GD symptoms corresponding to DSM-IV [38] or DSM-5 [39] GD criteria.

Results

Gambling Behaviors Among Veterans: Rates and Frequency

The US Government Accountability Office (GAO) reviewed the Military Health System records of the DOD and Coast Guard (CG) from fiscal year 2011 to 2015 and reported that less than 0.03% of the average number of active-duty service members each year were diagnosed with gambling disorder or seen for problem gambling within the healthcare system. The report also notes that neither the DOD nor the CG systematically screen for problem gambling. However, Congressional legislation passed in 2019, which required standard screening among US active-duty personnel in order to estimate the rates of GD diagnoses, but screening has not yet been widely implemented by DOD. Similarly US veterans, researchers observed a reported past-year GD rate of 0.2% in a large sample of 1,102,424 veteran users of VA mental health services [40••]. However, the GD rate in this study was determined by ICD-10 codes located in veterans’ medical records, which provides support for underdiagnoses of GD in this population. Viewing only the presence or absence of a diagnostic code does not provide accurate rate estimates, especially when considering that GD screening is uncommon in VA settings. Standardized screening for GD has not been widely implemented across the US VA hospitals or among active military members, which suggests that the diagnosed GD cases may only be severe presentations (e.g., legal or financial problems related to gambling). This is a possible explanation for the low rates of GD found by both reports and underestimates the actual rate of GD among US military members. Below, we will further review studies examining rate estimates of PG/GD among veterans within clinical and convenience samples, recognizing that precise estimates remain elusive at this time for veterans both within and outside of VA. Table 2 contains a summary with more detailed information on the rates of GD in veterans.

Table 2 Summary of studies investigating rates of gambling disorder
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The rates of GD found in other studies with clinical samples are much higher. For example, researchers reported that of 120 veterans receiving counseling at a VA center, 20% presented with “probable GD” (SOGS scores of > 5) and an additional 4.2% of veterans were classified as “problem gamblers” (SOGS scores of 3 or 4) [41]. The large increase in GD rates is likely because psychiatric and substance use disorders often co-occur with GD; therefore, higher rates of GD would be expected in a clinical sample. Lastly, a study by Westermeyer and colleagues found that a clinical sample of 1999 veterans showed weighted lifetime rates of 1.9% for GD and 8.8% for problem gambling [14••].

Several other studies aimed to examine GD rates in representative samples of veterans. One study estimated the rate of past-year at-risk/problem gambling to be 2.2% in a nationally representative sample of 3157 veterans [42]. In another study using the Vietnam Twin Era Registry (VET-R), investigators reported lifetime GD rates of 2.3% for veterans (n = 8169) from the Vietnam era [43]. Slightly higher rates were seen in a minority-based sample of 1228 American Indian and Hispanic veterans, as researchers found lifetime GD rates of 9.9% and 4.3%, respectively [44]. In the only study investigating both veteran and non-veteran GD rates, researchers found that for the overall sample (n = 9578), there was a problem gambling rate of 1.3% [45•]. For the veteran subsample, there was a significant increase in problem gambling rate, as 26 of the 923 veterans (2.8%) were classified as problem gamblers, which represented 20.6% of the overall number of problem gamblers. Additionally, in this subsample, 12.9% (n = 119) of veterans were represented in a combined at-risk/problem gambling group. However, it should be noted that this study only included veterans and non-veterans in the state of Massachusetts. A recent study examined GD rates in a cohort of current (n = 911) and former (n = 642) Ohio Army National Guard members and found a lifetime potential problematic gambling rate of 8% [13]. Furthermore, past-year frequent gambling (at least once per week) was demonstrated by 13% of the cohort.

Psychiatric Comorbidities with GD

GD is frequently comorbid with other psychiatric disorders, and it is important to study the possible effects of comorbidities, particularly when considering that veterans are at a higher risk compared with non-veterans for many psychiatric conditions [46]. Thus far, numerous studies have examined patterns and associations between GD and substance, alcohol, or nicotine use among veterans. Table 3 provides a summary of articles investigating psychiatric comorbidities of GD in veterans.

Table 3 Summary of studies examining gambling disorder and comorbidities
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A 1996 study showed that among hospitalized, treatment-seeking, substance-abusing veterans, 33% of veterans met criteria for comorbid substance abuse and GD [47]. Similarly, in a recent study of veterans receiving residential treatment for GD, 32.6% also had a current substance use disorder [48•]. Researchers also investigated substance use and gambling behaviors in veterans seeking substance use treatment at a VA program [49]. In this sample, 79% of veterans indicated that they experienced cravings/urges to gamble, and 27% of veterans reported problems due to gambling. Another study examined substance abuse patterns of veterans seeking treatment for GD and found that 66.4% of veterans reported a lifetime history of substance abuse or dependence [50]. Prior works also suggest that the onset of substance dependence preceded the onset of problem gambling. Researchers examined the association between nicotine dependence and comorbid psychiatric disorders in a representative sample of male, American Indian veterans [51]. The lifetime GD rate for these veterans was 9.4% and both current and lifetime nicotine dependence were associated with GD.

Some studies have focused more generally on the global psychiatric comorbidities of GD in veteran populations. One study found psychiatric profile differences when comparing a clinical sample of elderly (> 60 years) and younger veterans admitted to a VA hospital gambling treatment program [52]. This study found that the elderly cohort was just as likely as the younger cohort to carry a psychiatric diagnosis, but the younger cohort showed significantly higher psychiatric severity. In another treatment-seeking sample of veterans with GD, 41% of veterans showed a lifetime history of a mood disorder, 29.5% presented a lifetime diagnosis of PTSD, and 77% of veterans reported lifetime substance use [10]. Researchers examined rates of GD among American Indian and Hispanic veterans [53]. Specifically, they found that veterans in remission from GD (over the past year) were significantly less likely to have a current Axis I psychiatric diagnosis. The same research group again studied a representative sample of veterans, but now included only American Indian veterans [54]. However, this study differed from the previous in that the research team compared “non-problem” gamblers and non-gamblers and found that non-problem gamblers had greater lifetime rates of any mood disorder and PTSD.

PTSD and Trauma-Related Conditions

The relationship between PTSD and gambling behavior has become clearer in recent years, but more work remains to elucidate this relationship. Specifically, researchers found that gamblers were more likely to have a diagnosis of PTSD but no association was found between combat exposure and likelihood of gambling [54]. Similarly, in a study of a representative sample of veterans, researchers examined stressful life experience pre-, peri-, and post-deployment and found that veterans with PTSD were significantly more likely to engage in at-risk gambling behavior [15]. Specifically, this study showed that the experience of post-deployment stressful life events and less social support increased the probability of at-risk gambling behavior. Finally, a retrospective chart review of veteran admissions to a VA gambling treatment program found that 64% of veterans reported a history of trauma (emotional, physical, or sexual abuse) that usually occurred during childhood [55]. They also found that gamblers with trauma backgrounds that included experienced physical and emotional abuse were more likely to attempt suicide.

PTSD co-occurs at high rates among US veterans receiving residential problem gambling treatment. For example, a recent set of studies [28, 56] included both an inpatient clinical sample of veterans with GD and an online convenience sample of non-veterans, as they explored the relationship between gambling beliefs, motivations, and their association with symptoms of PTSD. Results from these studies indicated that for both samples, symptoms of PTSD were related to more general cognitive distortions around gambling, including positive gambling expectancies (beliefs that gambling will improve one’s affect, mood, or well-being). Additionally, PTSD was related to greater coping motivations for gambling (i.e., gambling to improve mood or reduce emotional distress). Moreover, both samples showed a positive relationship between positive gambling expectancies and coping motivations for gambling. Building off this previous study, these researchers used the same study design to further investigate symptoms of PTSD and how they might be related to specific situational vulnerabilities to gambling behaviors [48•]. This study found that for both veterans with GD and non-veterans, symptoms of post-traumatic stress were uniquely related to gambling in response to negative affect, gambling in response to social pressure, and gambling due to a need for excitement. These latter two points are somewhat surprising, as gambling in response to a need for excitement or social pressure were not predicted as situations that individuals with PTSD would be especially vulnerable to gamble. However, these associations persisted, even when other potentially explanatory variables were held constant (i.e., trait impulsivity). Furthermore, they persisted in a non-veteran community sample, suggesting a consistent link between PTSD symptoms and gambling in response to a wide variety of situations. Further work is needed to uncover the mechanisms and directionality involved in the relationship between GD and PTSD among veterans.

Suicide Risk

An estimated 1-in-5 individuals with problem gambling will attempt suicide in their lifetime [57,58,59]. A similar pattern has emerged for US veterans as one study found that 39.5% of 114 veteran compulsive gamblers had previously attempted suicide [60]. Furthermore, another study by the same author [52] compared younger and older cohorts of treatment-seeking veterans with GD and revealed that older veterans (age ≥ 60 years) were generally less likely to have attempted suicide at some point in the past. However, for recent suicide attempts in the last three years prior to gambling treatment admission, older veterans were more likely than the younger cohort to have attempted suicide. In a rare examination of suicide in a representative sample of veterans, researchers found that veterans who engaged in at-risk/problem gambling were significantly more likely to report a suicide attempt and suicidal ideation than recreational or non-gambling veterans [42]. Lastly, in a recent example, researchers revealed that in a clinical sample of veterans with GD and chronic pain, comorbid veterans were 1.9 times more likely to attempt suicide than veterans with a pain disorder alone [19••]. This result complements a previous work on chronic pain and GD, which suggested a positive association between moderate or severe pain interference and problematic/pathological gamblers in a sample of 41,897 adult Americans [61].

Taken together, these results raise considerable concerns about the increased risk for suicide that GD poses for military populations, but this association remains poorly understood. Considering the high rates of psychiatric disability associated with GD among veterans, greater attention is needed to routinely assess for suicidality and problem gambling severity among all active duty or veterans seeking healthcare.

Homelessness

Only two studies have investigated the relationship between homelessness and GD in veterans. An early study explored gambling problems in 154 formerly substance-abusing and homeless veterans six months after discharge from a treatment program [62]. Results from this study showed that veterans with gambling problems did not differ from other veterans in their current housing stability or employment. In a comparison of a national sample of homeless and non-homeless VA mental health users, researchers [63] discovered that in contrast to previous findings, GD was associated with homelessness and was a significant predictor of veteran homelessness (GD was the second strongest predictor after illicit drug use).

Table 4 provides an overview of studies exploring the factors of PTSD, trauma, homelessness, or suicide in gambling veterans.

Table 4 Summary of studies examining suicide, PTSD and trauma-related conditions, and/or homelessness in gambling veterans
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Treatment for GD in Veterans

The present review found two studies on the treatment of GD in military veterans within its scope, although there were previous treatment articles conducted at an earlier date than the studies included in this review [64]. The lack of treatment studies for GD in military personnel is concerning, particularly when considering that many military members are apprehensive about the confidentiality of their decision to seek treatment for GD [33]. An additional concern is that psychiatric disorders such as PTSD can co-occur at high rates among US veterans receiving residential problem gambling treatment [28, 56]. As such, the current strategies for treating GD in military members may be inadequate and should include plans to address likely psychiatric comorbidities and privacy concerns of US military members. Table 5 contains a summary of treatments of GD for veterans.

Table 5 Summary of studies exploring gambling treatments for veterans
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One study uniquely used a gambling treatment program that targeted 66 veterans’ gambling beliefs and attitudes [65]. The veterans that participated in this study showed significant improvement in gambling beliefs and attitudes at treatment end. In the only medication study found, the authors used disulfiram and naltrexone to treat 177 veterans with comorbid alcohol dependence, and co-occurring psychiatric disorders [66]. In a subsample of the 177 veterans, the authors found that 45 veterans exhibited problem-gambling features and these 45 veterans displayed significantly less improvement over time in global psychiatric functioning. In general, treatment interventions (psychotherapy, pharmacotherapy) targeting GD and other co-occurring disorders (PTSD, alcohol use disorder) among veterans remain understudied.

Vietnam Era Twin Registry (Genetic and Environmental Factors)

The following series of studies use data from the Vietnam Era Twin Registry (VET-R), which is a large cohort of only male twin pairs (both monozygotic and dizygotic) born between 1939 and 1957. All cohort members served in the Vietnam era (1965–1975), and in 1992 participated in a structured psychiatric interview that assessed for psychiatric diagnoses. The VET-R is a valuable dataset in that it allows researchers to examine genetic and environmental contributions to psychiatric diagnoses (including GD) in a large military population.

In one of the earliest studies, the investigators found that inherited factors explain between 35% and 54% of the liability for developing GD symptoms ([67]. Results also indicated that 62% of liability for a clinical diagnosis of GD can be explained by genetics and shared environment (familial factors). Lin et al.’s [67] results were also supported by a subsequent study [68] which found that 48.9% and 57.5% of the total variance in risk of lifetime or past-year GD symptoms, respectively, were due to genetic factors.

Other studies from the VET-R have explored how genetic factors impact GD and its comorbidities. For example, one study found baseline PTSD symptoms were associated with a higher risk of developing problem gambling 10 years later [69]. Other researchers found high rates of co-occurring lifetime GD and major depression (MD) with 34% of the genetic variance for GD/MD also contributing to that of the other disorder [70]. A 2015 analysis found that GD and obsessive-compulsive spectrum disorders had a shared genetic variance of 19.4% [71] which is similar to the 12–20% genetic variance shared between alcohol dependence and GD [72]. This research team also reported that 28% of the genetic variation in GD was accounted for by antisocial behavior disorders (ASPD, adult antisocial behaviors and childhood conduct disorder) [73]. Finally, several VET-R studies found that GD was associated with a host of attributes, including overall mental health, psychiatric disorders, and trauma history [25, 69, 74, 75•], with many of these associations still reaching significance after adjusting for covariates. For a complete summary of studies addressing genetic and environmental factors, see Table 6.

Table 6 Summary of studies addressing genetic and environmental contributions to gambling disorder in veterans
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Discussion

Given recent funding priorities put forth by DOD and a steadily-but-slowly growing body of literature on gambling behaviors and problems in military and veteran populations, we sought to conduct a systematic review of gambling-related research in veteran and military populations. Despite the increased and apparent vulnerabilities US military populations present for the development of GD, little research exists to provide a clear clinical and practical understanding of the disorder within this population. A clear understanding of its etiology, comorbidities, protective and risk factors, and prognosis remains mostly unexplored. Our review does suggest, however, that US military veterans have higher rates (estimated ranges between 2.3 and 9.0%) of GD (including problem gambling/at-risk problem gambling) [13, 43] compared with their civilian counterparts (estimated ranges between 0.4 and 4.0%) and that GD in the military service member populations often co-occurs with trauma-related conditions, substance use, and suicidality. Concerningly, there is a lack of published interventions tested in this unique population; and, like the general population, there appears to be a substantive genetic link to the development of the disorder and other psychiatric comorbidities [76]. Based on these factors, we have provided recommendations (see Table 7) on how to address missing gaps specific to problem gambling among US military populations.

Table 7 Knowledge gaps and concerns relating to GD in military veteran populations and approaches for addressing these issues
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With such limited research available, the apparent knowledge gaps are extensive as they pertain to problem gambling among US military populations. First, there is no clear, comprehensive understanding of the rates of problem gambling and GD among US military veterans. Prior work has provided some approximations of problem gambling among US veterans [42]; however, more research is needed to better understand how gambling severity evolves over the life course as well as differences across US military populations, particularly as a function of gender, ethnicity, and other cultural factors. It is likely that only in extreme cases of problem gambling are individuals diagnosed and referred to a mental health provider. Motivations for seeking gambling treatment among veterans are often the result of significant financial or legal factors [28]. To identify individuals with at-risk problem gambling (i.e., the beginning stages of the GD), we need to adopt standardized screening for problem gambling across healthcare settings that interact with military populations. The implementation of standardized screening for problem gambling could serve to detect those earlier in the course of the illness, thus reducing full onset of the GD, which in turn would prevent much of the irrevocable psychological, medical, social, and financial problems associated with problem gambling [77]. Results from this systematic review suggest that the implementation of standardized screening for GD among organizations (DOD military bases, Veterans Affairs Medical Centers, universities with veteran student programming) that serve US veterans is strongly needed.

Second, our review suggests there are limitations with current studies specific to the design and samples used for assessing problem gambling/GD among veterans. With only a few exceptions, samples studied were convenience samples, often treatment-seeking, and designs were cross-sectional in nature. In addition, any comparisons made between diagnosed GD, problem gamblers, recreational gamblers, and non-gamblers amount to only a small fraction of studies. Slot machines are widely available on US military bases [78] which may play a role in the initial development of GD in military members [79]. Yet, these direct links remain untested. In the future, more exploration of the etiology of GD in military members and veterans is necessary, particularly as it pertains to understanding how gambling accessibility on military bases increases veterans’ risk of developing GD. Ultimately, there are relatively few substantive examples of prospective research studies specifically investigating gambling behaviors and GD in veteran populations. Prospective studies of GD in US military members would assist researchers in unveiling the specific risk factors (e.g., trauma exposure, impulsivity, adverse childhood experiences) that might lead to the development of GD and in identifying potential protective factors that lower the chance of developing GD. Moreover, such research would also provide foundations for future policy initiatives in military and veteran populations designed to prevent the development of gambling problems before they appear.

Third, the majority of samples studied included white, male veterans. Although reflective of the armed services demographics overall, findings from the general population demonstrate that GD affects minorities differently and at greater rates and should also be considered within this subpopulation of US military veterans. This is particularly notable given that all branches of the military are increasingly diverse with regard to gender and racial composition [80]. In addition, the progression of problem gambling and GD differs between men and women in the general population [81], and although men make up the majority of US military veterans population, the percentage of women joining the US military service continues to rise. Recent studies have also raised attention to GD among women veterans, which requires further exploration [19•]. This focus on gender differences is particularly notable given that recent studies of veterans in residential treatment for GD were comprised of 20% women, which suggests that either rates of GD or rates of treatment-seeking (or both) may be higher among women veterans [28, 56]. Lastly, evidence suggests that age may also play a role in how GD presents and its co-occurring risk factors (e.g., suicide); yet, despite the aging US veteran population, little is known about how gambling behaviors differ across the lifetime in veterans. With a large and aging US veteran population, further work examining the interplay between age and GD among veterans is sorely needed as prior work has suggested that problem gambling occurs across the lifespan and is present among older adults [82].

Lastly, with only two extant treatment studies within the scope of this review, one psychosocial and one pharmacological, it is unclear how effective treatment within the general population will translate to the US veteran population. Because of the complex and unique histories and co-occurring disorders found among US military veterans, standard treatment protocols often need to be adapted to meet their specific needs. Given that, there is a great need to further investigate and develop effective treatments for this subpopulation and other at-risk groups [83].

As mentioned above, the US GAO (2017) reported a small number of active-duty service members were diagnosed with GD or were being treated for problem gambling. Yet, despite these low numbers, the GAO report suggests active screening for problem gambling given its association with its problematic preoccupation, financial problems, and an increased risk of suicide. In 2019, US Senators Warren and Daines introduced an updated Gambling Addiction Prevention (GAP) Act, which requires the DOD to develop policies and programs to prevent and treat problem gambling, provide education materials and programs, and to promote responsible gaming on military sites where gambling is available. In addition, within 180 days of the passage of the Act, it requires the DOD to update its regulations, instructions, and guidance to explicitly include gambling disorder. The exact nature of the screening, programs, and intervention have yet to be determined among US agencies that serve military populations. As such, this remains a significant barrier to care for veterans/active-duty personnel with GD.

As a natural corollary to the field’s limitation and the DOD and VA policy changes proposed internally, future directions are clear. First, a systematic, prospective study specific to the study of problem gambling among US military veterans is needed to determine effective screeners for identifying those at risk and to better understand development of the disorder to help determine points for intervention. Second, investigation into the clinical comorbidities of problem gambling is also needed due to higher rates of psychiatric (e.g., PTSD) and substance use disorders (e.g., alcohol use disorder) and suicide among US veterans [42]. Likewise, further investigation is needed to determine the role of gambling in social and financial issues (e.g., homelessness). In addition, less is known about possible differences in specific characteristics regarding associated cognitive distortion and symptom severity of GD among this population is needed. A better understanding of gambling characteristics and co-occurring problems among this population will inevitably lead to improved interventions and treatment that appropriately target their unique needs, which leads to the next gap: demonstrated effective treatment. Our review found only two interventions for problem gambling among US veterans. Once problem gambling is identified, demonstrated effective treatments need to be studied, developed, and tailored to this population to ensure it adequately addresses their specific needs and leads to recovery. Pharmacotherapy and psychotherapy interventions designed to treatment GD among US veterans are strongly needed to address missing gaps in care for this vulnerable subpopulation (see [76] for further discussion).

Despite the varying reports and studies of varying samples, design, and methodologies and the apparent knowledge gaps, as this review demonstrates, US military veterans are vulnerable to the development of problem gambling and GD. Unlike the general population, however, the extent of the problem and effective treatments for GD remain unknown and untested. Future research is needed to address many of the described missing gaps needed to enhance diagnosis and treatment outcomes for veterans with gambling problems.