The essence of the neurobiology of suicidal behavior is that a specific vulnerability to suicidal behavior is mediated by an underlying genetic predisposition interacting with environmental stressors and probable epigenetic factors throughout the lifespan to modify the function of neuronal circuits, thus rendering an individual more likely to engage in a suicidal act.

This chapter will introduce the methods by which the behaviors and models discussed in the previous two chapters are studied. This chapter will thus provide the reader with a foundation of neuroscience techniques from which they can build upon with information in the remainder of the book. These techniques address (epi-)genetics and functional neuro-anatomy.

Neuroscience approaches to the study and understanding of suicidal behavior may differ somewhat from those targeting other behavioral issues. As suicide appears to be a unique human behavior, there is a lack of animal models. However, much information is available from postmortem studies of brain tissue, in which brain characteristics of suicide victims are compared to those of individuals who died from other causes. Postmortem studies are sometimes accompanied by psychological autopsies, which are standardized interviews with individuals who were in close contact with the deceased, covering a wide range of health- and personality-related issues.

A particular case of a suicide attempt by a young girl has inspired a career, that has resulted in this book. This chapter describes the story of the girl, and indicates why and how neuroscientific studies may contribute to the prevention of suicidal behavior by means of an overview of the chapters in this book.

Computational neuroscience uses formal models of brain function to characterize the mechanisms behind behavioral problems. The production of false beliefs and their behavioral consequences are a central issue in such models. Hopelessness and suicidal thoughts are examples of such false beliefs that commonly lead to suicidal behavior as a consequence. In normal everyday life, people update their beliefs based on what they perceive: bottom-up sensory inputs are compared with top-down beliefs, and mismatches are signaled as prediction errors. Neurobiological correlates of belief updating are increasingly demonstrated. Cortical activations as demonstrated in functional neuroimaging studies, such as those reported in Chapter 6, thus reflect the production of prediction errors that signal a mismatch between beliefs and perceptual information. These errors can be minimized in several ways: beliefs can be updated, or sensory input can be minimized by withdrawal into oneself or escape from this world. If something goes wrong in this process of belief updating, false beliefs may develop and persist despite perceptual proof of the opposite. This chapter will describe a predictive coding model of suicidal behavior, in which findings from neurocognitive, neuroimaging, and neurobiological studies can be integrated. This model leads to a new understanding of suicide and, consequently, to new approaches to prevention.

Children who have experienced sexual or physical abuse during childhood are at increased risk of suicidal behavior in adulthood, independent of other factors such as depression. Recent neurobiological studies target the mechanisms that link childhood abuse and suicidal behavior in adulthood. How does early-life adversity influence behavioral reactions to stressors much later in life to such an extent that people take their own lives? It is now becoming clear that early-life adversity increases the risk of suicide by influencing the development of stable emotional, behavioral and cognitive characteristics that confer a specific vulnerability. There is now considerable evidence that changes in the expression of particular genes constitute the molecular basis of this vulnerability. This chapter will review recent findings from genetic studies of suicidal behavior, with a particular focus on epigenetic regulation of the hypothalamic–pituitary–adrenal axis and other systems involved in responses to stress and on transcriptional changes in association with early-life adversity. It appears that such changes may become manifest as cognitive impairments that are commonly found in association with suicidal behavior, and that may be due to structural and functional alterations in the brain.

This chapter provides an introduction to the book by providing a basic understanding of suicidal behavior. It first provides the reader a general knowledge of the epidemiological, clinical, and behavioral presentations of suicidal behaviors. In many situations, acts of nonfatal suicidal behavior will precede lethal suicidal behavior, and a suicidal process with clear implications for prevention is commonly found. The multiple causes of suicidal behaviors will be discussed, and it will become clear that each suicide results from a complex convergence of many possible sociocultural and neurobiological (e.g. genetic) factors. In spite of the unique characteristics of each suicide in terms of personal features and social circumstances, many such suicides can be understood as the consequence of an interaction between stressors and a specific vulnerability to suicidal behavior. Stressors may include problems in relational, professional, or financial areas, or consequences of psychiatric disorders such as depression that may precipitate suicidal behavior in vulnerable individuals. It is particularly with regard to this vulnerability that neuroscience studies have contributed substantially to our insights, and thus provide opportunities for prevention and treatment.