DESPITE the clinical importance of suicide prevention, this topic has received very little attention within the field of brain injury rehabilitation. In 1950s and 1970s, results from early outcome studies of civilian and veteran cohorts with traumatic brain injury (TBI) documented higher numbers of suicides than would be expected in the general population.1-6 Notwithstanding these initial findings, the following 2 decades saw sporadic attention paid to studying this important area of postinjury adjustment, with only 2 articles, both published in this journal, that specifically addressed the issue.7,8 However, in the past 10 years, there has been a quickening of interest. Population and large-sample epidemiological studies have attested to significantly elevated levels of suicide,9-11 suicide attempts,12 and suicide ideation13 among people with TBI in comparison with the general population.

The upsurge in interest is due in part to initiatives undertaken by the Department of Veterans Affairs in the United States. Historically, rates of suicide among US military personnel were lower than the general population; however, since 2005, the suicide rate in the army has exceeded general population levels.14 This climb has occurred despite increased efforts and programs for suicide prevention and intervention.14 In addition, a characteristic of the recent conflicts in Iraq and Afghanistan has been the high number of military personnel sustaining TBIs.15 In response to such developments, there has been growing concern regarding both suicidal behavior among these injured veterans and TBI as a risk factor for suicide. In 2005, the Veterans Integrated Service Network 19, Mental Illness Research Education and Clinical Center (MIRECC), was established with the goal of increasing understanding regarding suicide prevention among military veterans. Toward this goal, one of the MIRECC's objectives has been to study the cognitive and neurobiological underpinnings of suicidality. Research regarding veterans with a history of TBI has been a specific area of interest. It is believed that focusing on this population will help to decrease suicide among this high-risk group and increase understanding regarding the relationship between neuropsychological functioning and suicide among the general population of veterans. See http://www.mirecc.va.gov/visn19/ for further information regarding the Veterans Integrated Service Network 19, MIRECC. Parallel to this development, a research program funded in part by the National Health and Medical Research Council of Australia and based at the Brain Injury Rehabilitation Unit, Liverpool Hospital in Sydney, has been investigating suicide and suicide prevention among civilians with TBI for more than a decade.

Drawing on these 2 streams, this special issue brings together an unparalleled concentration of research on the topic of suicide, suicide prevention, and TBI spanning civilian and veteran populations. Given the embryonic nature of the literature, we have sought to showcase a range of different perspectives that both inform and highlight avenues for further action. The articles canvass clinical, population, neurobiological, and treatment perspectives, with an emphasis on empirical research. Although the majority of articles were generated in the United States, it is our hope that many of the findings will have cross-national relevance.

The initial article by Dennis and colleagues sets the scene, providing a review of suicide nomenclature, epidemiology, and risk and protective factors. An overview regarding evidence-informed suicide risk assessment, management, and treatment practices is also presented. The authors highlight the importance of identifying the unique deficits of each individual with a history of TBI and suicidality and tailoring interventions to address functional limitations.

We then shift the perspective to 2 articles that focus on the prevalence and correlates for different types of suicidal behavior. Brenner and colleagues report on elevated rates of completed suicide in those with TBI among the population of individuals seeking care within the Veterans Health Administration. Controlling for psychiatric and demographic factors, they found that veterans with TBI were 1.55 times more likely to die by suicide than the general veteran population, with the rate rising to 1.98 for those veterans who had sustained a concussion/cranial fracture. This article provides the first systematic examination of suicide among military veterans with TBI since the 1971 publication of Achte and colleagues,4 who investigated the suicides of 85 brain-injured Finnish veterans over a 25-year follow-up period after the Second World War. The study by Brenner and colleagues adds further weight to the evidence base documenting elevated suicide rates after TBI, and in turn, continues to build a case for the inclusion of TBI as an "at-risk" group in national and international suicide data collection protocols and suicide prevention guidelines.

Mental health disorders are a major factor associated with suicide. Tsaousides and colleagues have focused on the prevalence of suicide ideation among civilians with TBI who have various psychiatric diagnoses. They found that participants who met criteria for a psychiatric diagnosis of depression, anxiety, or posttraumatic stress disorder were more likely to report suicide ideation. They also examined the influence of a range of premorbid, demographic, injury, neuropsychological, and postinjury psychosocial variables and found that participants displaying suicide ideation also reported significantly lower levels of psychosocial functioning. Neuropsychological performance was not related to suicide ideation.

The next shift of perspective turns the focus onto the neurobiological mechanisms underpinning suicidal behaviors. Research into the neurobiology of suicide among psychiatric and other populations has highlighted several candidate neuronal and neurochemical mechanisms that may be associated with elevated risk. To the best of our knowledge, the neuroimaging article by Yurgelun-Todd and colleagues is the first to investigate potential links between the pathophysiology of TBI and postinjury suicidality. Findings suggested a significant reduction in fractional anisotropy in frontal white matter tracts among veterans with a history of mild TBI. Decreased fractional anisotropy values were also associated with suicidal ideation and impulsivity. Results provide further support for the potentially important relationships between suicidal ideation, behavioral disinhibition, and frontal-limbic dysfunction.

Despite the growing body of evidence, which suggests that individuals with a history of TBI are at significantly increased risk for dying by suicide, best clinical practice has been guided by expert consensus rather than empirical findings. There continues to be a dearth of evidence-based suicide prevention treatments for those with TBI. The final article in the collection reports on a phase II randomized controlled trial that evaluated the efficacy of a psychological treatment program for hopelessness, a risk factor for suicidal behavior after severe TBI. Participants in the treatment group reported significant reductions in hopelessness compared to waitlist controls, as well as a trend to reduced levels of suicide ideation. Moreover, 3 quarters of the treatment group maintained the gains or improved even further at a 3-month follow-up. Although this study represents an important step forward in suicide prevention efforts, further work is required to replicate these initial positive findings.

Presented articles only begin to address the complex problem of suicide among those with TBI. In terms of future work, it will be important to foster further theory-driven research. Constructs such as the diathesis-stress model need testing to examine their explanatory and predictive power in relation to suicidality after TBI. Such research could then drive the development of evidence-based assessment and treatment practices. Additional focus is also required to elucidate both risk factors and protective factors that mediate the levels of suicidality experienced by people with TBI. Examples of risk factors that have been highlighted in the literature, but are yet to be investigated empirically include impairments in executive function such as impulsivity, aggression, and poor decision making.

Significant heterogeneity exists among those with a history of TBI. Although increased risk for suicide has been identified across the severity continuum, it is likely that risk and protective factors for those with mild injuries versus severe injuries vary. For example, it may be that among those with mild TBI, the history of both injury and suicide is related to a third variable, general risk-taking behavior, and this important issue requires further investigation. Finally, recent research among non-brain-damaged groups has investigated warning signs (eg, precipitating emotions, thoughts, or behaviors), which are proximal to suicidal behavior and are believed to imply imminent risk. Identifying such warning signs is therefore an important component of risk assessment and treatment planning.16 Additional work is required to explore the concept of warning signs among those with TBI.

Effective suicide prevention requires action on many different fronts. Evidence-based data for the pharmacological or psychological treatments for depression are still in their infancy, but for some with TBI, such treatments are likely to have flow through effects, reducing suicidality. The organizational challenges of maintaining appropriate suicide prevention policies and clinical pathways, ensuring staff training, reducing the lethality of the local environment, implementing appropriate screening measures, and developing collaborative relationships with mental health services are also important issues that require study. Finally, there are significant intra- and international variations in suicide rates, risks, and behavior, creating the necessity for locally generated research and initiatives in this field.

Given that the current body of research is quite limited, there is a real opportunity to achieve significant uniformity in the nomenclature and measures that are employed by researchers, thereby making the most of the benefits that accrue from future research endeavors. Collaboration between research programs focusing on civilian and veteran populations will also help investigators maximize the outputs from limited research resources. Moreover, such joint efforts are vital in light of the low base rates of suicidal behaviors and subsequent challenges associated with obtaining adequate sample sizes.

The great majority of people with TBI who display suicidal behaviors survive, but a small minority does not survive and go on to end their lives. The World Health Organization (WHO) holds to the position that suicide is largely preventable.17 This presents both a challenge and a hope to our field. In the clinical sphere, to meet this challenge involves a consideration of how the detection, assessment, management, and prevention of suicide after TBI can be addressed. The WHO asserts that suicide prevention is everybody's business,18 and in the field of TBI, the expertise of all stakeholders, including neuropsychiatry, psychology, rehabilitation medicine, nursing, allied health, primary healthcare and community support systems, advocacy organizations, insurers, families, and individuals with TBI themselves, can make a contribution. Through rising to meet such challenges, we can realize the hope that by increasing our efforts to understand and effectively intervene, we may ultimately reduce the number of suicide attempts and deaths after TBI.

-Grahame K. Simpson, PhD

Senior Research Fellow

Brain Injury Rehabilitation Unit

Liverpool Hospital, Sydney, Australia

Rehabilitation Studies Unit

University of Sydney, Australia

-Lisa A. Brenner, PhD

Director

Department of Veterans Affairs

VISN19 Mental Illness Research

Education and Clinical Centre

Denver, Colorado

Associate Professor

Denver School of Medicine University

of Colorado

REFERENCES