We all have an innate drive to keep ourselves alive. We eat when we are hungry, get out of the way of fast-moving vehicles, and go to school so we can earn a living to keep ourselves and our families alive (see the discussion of evolutionary psychology in the Psychology: Evolution of a Science chapter). One of the most extreme manifestations of abnormal human behavior is when a person acts in direct opposition to this drive for self-preservation and engages in intentionally self-destructive behavior. Accounts of people intentionally harming themselves date back to the beginning of recorded history. However, it is only over the past several decades that we have begun to gain an understanding of why people purposely do things to hurt themselves. DSM–5 includes two self-destructive behaviors in a special section on disorders in need of further study: suicide behavior disorder and nonsuicidal self-injury disorder.

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Tim, a 35-year-old accountant, had by all appearances been living a pretty happy, successful life. He was married to his high school sweetheart and had two young children. Over the past several years, though, his workload had increased, and he started to experience severe job-related stress. At around the same time, he and his wife began to experience some financial problems, and his alcohol consumption increased, all of which put significant strain on the family and began to affect his work. One evening, after a heated argument with his wife, Tim went into the bathroom and swallowed a bottle full of prescription medicine in an effort to end his life. He was taken to the hospital and kept there to be treated for suicidal behavior.

Suicide, which refers to intentional self-inflicted death, is the 10th leading cause of death in the United States and the 2nd leading cause of death among people 15 to 24 years old. It takes the lives of more than 5 times as many people as HIV-AIDS each year in the United States, and more than twice as many people as homicide (Hoyert & Xu, 2012). Approximately 80% of all suicides occur among men, and in the United States, White people are much more likely to kill themselves than members of other racial and ethnic groups, accounting for 90% of all suicides (Centers for Disease Control and Prevention, 2013). Unfortunately, we currently do not have a good understanding of why these enormous sociodemographic differences exist.

A nonfatal suicide attempt, which refers to a self-inflicted injury from which a person has at least some intention of dying, occurs much more frequently than suicide deaths. In the United States, approximately 15% of adults report that they have seriously considered suicide at some point in their lives, 5% have made a plan to kill themselves, and 5% have actually made a suicide attempt. Although many more men than women die by suicide, women experience suicidal thoughts and (nonfatal) suicide attempts at significantly higher rates than do men (Nock et al., 2008). The rates of suicidal thoughts and attempts are virtually nonexistent before age 10, but then they increase dramatically from age 12 to 18 years (see FIGURE 14.5) before leveling off during early adulthood (Nock et al., 2013).

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So the numbers are staggering, but why do people try to kill themselves? The short answer is: We do not yet know, and it’s complicated. When interviewed in the hospital following a suicide attempt, most people who have tried to kill themselves report that they did so in order to escape from an intolerable state of mind or impossible situation (Boergers, Spirito, & Donaldson, 1998). Consistent with this explanation, research has documented that the risk of suicidal behavior is significantly increased if a person experiences distressing factors such as the presence of multiple mental disorders (more than 90% of people who die by suicide have at least one mental disorder); significant negative life events during childhood and adulthood (e.g., physical and sexual assault); and severe medical problems (Nock, Borges, & Ono, 2012). The search is ongoing for a more comprehensive understanding of how and why some people respond to negative life events with suicidal thoughts and behaviors, as well as on methods for better predicting and preventing these devastating outcomes.

Louisa, an 18-year-old college student, secretly cuts her lower waist and upper thighs about once per week, typically when she is in the midst of feeling intense anger and hatred, either toward herself or someone else. She was 14 when she started using self-injury as a way to calm herself down. Louisa says that she actually feels a little ashamed after each episode of cutting, but she doesn’t know how else to calm down when she gets really upset and so she has no plans of stopping this behavior.

Louisa is engaging in a behavior called nonsuicidal self-injury (NSSI), the direct, deliberate destruction of body tissue in the absence of any intent to die. NSSI has been reported since the beginning of recorded history; however, it appears to be on the rise over the past few decades. Recent studies suggest that as many as 15 to 20% of adolescents and 3 to 6% of adults report engaging in NSSI at some point in their lifetimes (Klonsky, 2011; Muehlenkamp et al., 2012). The rates appear to be even between males and females, and for people of different races and ethnicities. Like suicidal behavior, NSSI is virtually absent during childhood, increases dramatically during adolescence, and then appears to decrease across adulthood.

In some parts of the world, cutting or scarification of the skin is socially accepted, and in some cases, it is even encouraged as a rite of passage (Favazza, 2011). In parts of the world where self-cutting is not socially encouraged, why would a person purposely hurt him- or herself if not to die? Recent studies suggest that people who engage in self-injury have very strong emotional and physiological responses to negative events, that they perceive this response as intolerable, and that NSSI serves to diminish the intensity of this response (Nock, 2009). There also is some evidence that in many instances, people engage in self-injury as a means to communicate distress or elicit help from others (Nock, 2010).

Unfortunately, much like suicidal behavior, our understanding of the genetic and neurobiological influences on NSSI is limited, and there currently are no effective medications for these problems. There also is very limited evidence for behavioral interventions or prevention programs (Mann et al., 2005). So, whereas suicidal behavior and NSSI are some of the most disturbing and dangerous mental disorders, they also, unfortunately, are among the most perplexing. The field has made significant strides in our understanding of these behavior problems in recent years, but there is a long way to go before we are able to predict and prevent them accurately and effectively.

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