Epidemiology

Suicide accounts for 1.3% of the total number of deaths in the United States each year.^1,8 For every person who completes suicide, approximately 8 to 10 people attempt suicide.^9,10 Although no nationwide data on annual attempted suicides are available, research indicates that for every completed suicide, approximately 8 to 25 attempts are made^11–13; that is, some individuals make more than one unsuccessful attempt. Each year, emergency departments treat approximately 500,000 suicide attempters.^14,15 These visits represent approximately 0.5% of all annual emergency department visits.^2,14

Use of firearms is the most common method of committing suicide for both men and women in the United States, accounting for between 50% and 60% of annual suicides.^12,13 Suffocation, including hanging, is the second most common cause of suicide overall in the United States, and the second most common cause in men, accounting for approximately 6,500 suicide deaths per year.^15,16 Poisoning, including drug ingestion, is the third most common cause of completed suicide in the United States and the second most common cause in women, accounting for approximately 5,500 deaths per year.^15,16 Historically, drug ingestion has accounted for the majority of unsuccessful suicide attempts.^17,18

Suicide rates differ by age, gender, and race. Rates generally increase with age; people older than age 65 are 1.5 times more likely to commit suicide than are younger individuals, while white men over age 85 have an even higher rate of suicide.^14,19,20 The number of suicides in the elderly is disproportionately high; the elderly appear to make more serious attempts on their lives and are less apt to survive when medical complications from an attempt ensue—one out of four attempts in this group results in a completed suicide.^19–21 Although the elderly have the highest suicide rates, suicide in young adults (between ages 15 and 24) rose threefold between 1950 and 1990, becoming the third leading cause of death following unintentional injuries and homicide.^12,22,23 Since that time, the suicide rate has declined in adolescents.²³ Men are more likely to complete suicide than are women, although women are more likely to attempt suicide than are men. Four times more men than women complete suicide,^8,24 although women are three to four times more likely than men to attempt suicide.^24,25 The reasons for these disparities have not been established clearly.

Whites and Native Americans attempt and commit suicide more than nonwhites.^5,12,24 African Americans and Hispanics have approximately half the suicide rate of whites.^24,26,27

Psychiatric Risk Factors

Psychiatric illness is the most powerful risk factor for both completed and attempted suicide. Psychiatric disorders are associated with more than 90% of completed suicides^3,4,24,28 and with the vast majority of attempted suicides.^5–7 Mood disorders, including major depressive disorder (MDD) and bipolar disorder, are responsible for approximately 50% of completed suicides, alcohol and drug abuse for 25%, psychosis for 10%, and personality disorders for 5%^29,30 (Table 53-2).

Table 53-2 Percentage of Suicides with a Given Psychiatric Disorder

Up to 15% of patients with MDD or bipolar disorder complete suicide, almost always during depressive episodes³¹; this represents a suicide risk 30 times greater than that of the general population.^32,33 True lifetime risk may be somewhat lower, because these estimates (and those for the other diagnoses discussed later) typically derive from hospitalized patient samples.²⁹ The risk appears to be greater early in the course of a lifetime disorder, early on in a depressive episode,^11,34 in the first week following psychiatric hospitalization,³⁵ in the first month following hospital discharge,³⁵ and in the early stages of recovery.³⁵ The risk may³⁶ or may not³⁷ be elevated by co-morbid psychosis. A 10-year follow-up study of almost 1,000 patients found that those who committed suicide within the first year of follow-up were more likely to be suffering from global insomnia, severe anhedonia, impaired concentration, psychomotor agitation, alcohol abuse, anxiety, and panic attacks, whereas those who committed suicide after the first year of follow-up were more likely to be suffering from suicidal ideation, severe hopelessness, and a history of suicide attempts.³⁶

Approximately 15% to 25% of patients with alcohol or drug dependence complete suicide,^34,38 of which up to 84% suffer from both alcohol and drug dependence.³⁸ The suicide risk appears to be greatest approximately 9 years after the commencement of alcohol and drug addiction.^3,39 The majority of patients with alcohol dependence who commit suicide suffer from co-morbid depressive disorders,^34,40,41 and as many as one-third have experienced the recent loss of a close relationship through separation or death.⁴²

Nearly 20% of people who complete suicide are legally intoxicated at the time of their death.⁴³ Alcohol and drug abuse are associated with more pervasive suicidal ideation, more serious suicidal intent, more lethal suicide attempts, and a greater number of suicide attempts.⁴⁴ Use of alcohol and drugs may impair judgment and foster impulsivity.^35,45

Approximately 10% of patients with schizophrenia complete suicide, mostly during periods of improvement after relapse or during periods of depression.^41,46,47 The risk for suicide appears to be greater among young men who are newly diagnosed,^47–49 who have a chronic course and numerous exacerbations, who are discharged from hospitals with significant psychopathology and functional impairment, and who have a realistic awareness and fear of further mental decline.^47,49 The risk may also be increased with akathisia and with abrupt discontinuation of neuroleptics.³⁴ Patients who experience hallucinations (that instruct them to harm themselves) in association with schizophrenia, mania, or depression with psychotic features are probably at greater risk for self-harm and they should be protected.⁵⁰

Between 4% and 10% of patients with borderline personality disorder and 5% of patients with antisocial personality disorder commit suicide.⁵¹ The risk appears to be greater for those with co-morbid unipolar depression or alcohol abuse.^52,53 Patients with personality disorders often make impulsive suicidal gestures or attempts; these attempts may become more lethal if they are not taken seriously. Even manipulative gestures can turn fatal.⁵⁰

As many as 15% to 20% of patients with anxiety disorders complete suicide,⁵⁴ and up to 20% of patients with panic disorder attempt suicide.⁵⁵ Although the risk of suicide in patients with anxiety and panic disorders may be elevated secondary to co-morbid conditions (e.g., MDD and alcohol or drug abuse), the suicide risk remains almost as high as that of major depression, even after co-existing conditions are taken into account.⁵⁶ The risk for suicide attempts may be elevated for women with an early onset and with co-morbid alcohol or drug abuse.⁵⁵

Medical Risk Factors

Medical illness, especially of a severe or chronic nature, is generally associated with an increased risk of suicide and is thus considered a risk factor for completed suicide even though there is a most likely a multifactorial relationship between medical illness and suicide.^16,57,58 Medical disorders are associated with as many as 35% to 40% of suicides⁵⁹ and with as many as 70% of suicides in those older than age 60.⁶⁰ Acquired immunodeficiency syndrome (AIDS), cancer, head trauma, epilepsy, multiple sclerosis, Huntington’s chorea, organic brain syndromes, spinal cord injuries, hypertension, cardiopulmonary disease, peptic ulcer disease, chronic renal failure, Cushing’s disease, rheumatoid arthritis, and porphyria have each been reported to increase the risk of suicide. Notably, however, few investigations concerning the increased risk for suicide in these populations have controlled for the effects of age, sex, race, psychiatric disorders, other medical disorders, or use of medications.

Patients with AIDS appear to have a suicide risk that is greater than that of the general population, and estimates of the increased risk range from 7 to 66 times greater than the general population.^29,61,62 It is generally accepted that the risk of suicide in human immunodeficiency virus (HIV) infection is increased approximately sevenfold.^16,61 Testing for antibodies to HIV virus has resulted in an immediate and substantial decrease in suicidal ideation in those who turned out to be seronegative; no increase in suicidal ideation was detected in those who were seropositive.⁶³ Sexual orientation among men, in and of itself, has not been identified as an independent risk factor for completed suicide.^12,64

Cancer patients have a suicide rate that is almost twice as great as that of the general population and seem to be at higher risk in the first 2 years after they are diagnosed.^61,65 Head and neck malignancies are associated with an 11 times greater risk of suicide compared with the general population, possibly due to increased rates of tobacco and alcohol use in this population and the resultant facial disfigurement and loss of voice.⁶¹ In men, gastrointestinal cancers are associated with a greater risk of suicide, and in both sexes lung and upper airway malignancies are also associated with greater suicide risk.⁶¹ Other factors, including poor prognosis, poor pain control, fatigue, depression, hopelessness, delirium, disinhibition, prior suicide attempts, recent losses, and a paucity of social supports, may place cancer patients at greater risk.^66,67

Like cancer patients, individuals with head trauma, multiple sclerosis, and peptic ulcer disease have approximately twice the risk of suicide of the general population.^61,68,69 In patients with head injuries, the risk appears to be greater in those who suffer severe injuries and in those who develop dementia, psychosis, character changes, or epilepsy.^68–70 In patients with multiple sclerosis, the risk may be higher for those diagnosed before age 40 and within the first 5 years after diagnosis.⁷¹ In patients with peptic ulcer disease, the increased risk is hypothesized to be due to co-morbid psychiatric and substance use (especially alcohol) disorders.^61,70

Between the increased risk of suicide of approximately twofold for cancer, head trauma, multiple sclerosis, and peptic ulcer disease, and the increased risk in HIV-infected/AIDS patients estimated to be at least nearly sevenfold, there are a number of medical illnesses with intermediate increases in suicide risk. These illnesses include epilepsy, systemic lupus erythematosus, spinal cord injuries, Huntington’s disease, organic brain syndromes, and chronic renal disease. Patients with end-stage renal disease on hemodialysis may have the highest relative risk of all subgroups.^61,72 As many as 5% of patients with chronic renal failure who receive hemodialysis die from suicide; those who travel to medical centers for dialysis have a higher suicide rate than those who are dialyzed at home.¹⁰ The risk for suicide among these patients may be as high as 400 times that of the general population.⁷³

Patients with epilepsy are five times more likely than those in the general population to complete or to attempt suicide.^61,74–76 Sufferers of temporal lobe epilepsy, with concomitant psychosis or personality changes, may be at greater risk.^61,74,75,77

Delirious and confused patients may suffer from agitation and destructive impulses and be unable to protect themselves from harm.⁶⁶ In victims of spinal cord injury, the risk is actually greater for those with less severe injuries.^78,79

Hypertensive patients⁷⁰ and those with cardiopulmonary disease⁵⁰ may also have a higher risk for suicide than those in the general population. Although previous reports suggested that beta-blockers could contribute to increased risk by promoting depression,⁷⁰ recent studies suggest that beta-blockers do not increase the risk of developing depression.⁸⁰ Finally, an association between suicide and very low cholesterol levels has been reported, but the connection is still under investigation.^16,29

Familial and Genetic Risk Factors

A family history of suicide, a family history of psychiatric illness, and a tumultuous early family environment have each been found to have an important impact on the risk for suicide.^12,59 As many as 7% to 14% of persons who attempt suicide have a family history of suicide.⁸¹ A family history of suicide confers approximately a twofold increase in risk for suicide after family psychiatric history is controlled for.⁸² This increased suicide risk may be mediated through a shared genetic predisposition for suicide, psychiatric disorders, or impulsive behavior,^34,48,83 or through a shared family environment in which modeling and imitation are prominent.⁸⁴

Genetic factors are supported by evidence that monozygotic twins have a higher concordance rate for suicide and suicide attempts than dizygotic twins and by evidence that biological parents of adoptees who commit suicide have a higher rate of suicide than do biological parents of nonsuicidal adoptees.^29,83,85 However, little is known about the specific genetic factors that confer this risk.²⁹ Study has largely focused on serotonin neurotransmission, including genetic mutations in the rate-limiting enzyme in serotonin syn-thesis, L-tryptophan hydroxylase, serotonin receptors, and the serotonin transporter, but this investigation is still preliminary.^82,86–88 Overall, it is estimated that one-third to one-half the risk of suicide is genetically mediated.⁸²

Numerous familial environmental factors may also contribute to suicide risk. A tumultuous early family environment (including factors of early parental death, parental separation, frequent moves, and emotional, physical, or sexual abuse) increases the risk for suicide.⁸⁹ Children’s risk of future suicidal behavior may also be increased by suicidal behavior in important family members through modeling.²⁹

Social Risk Factors

Widowed, divorced, or separated adults are at greater risk for suicide than are single adults, who are at greater risk than married adults.^90,91 Married adults with young children appear to carry the lowest risk.^35,50,59 Living alone substantially increases the risk for suicide, especially among adults who are widowed, divorced, or separated.³⁵ Social isolation from family, relatives, friends, neighbors, and co-workers also increases the chance of suicide.^48,59 Conversely, the presence of social supports is protective against suicide.⁸²

Significant personal losses (including diminution of self-esteem or status^59,60) and conflicts also place individuals, particularly young adults and adolescents, at greater risk for suicide.^3,92 Bereavement following the death of a loved one increases the risk for suicide over the next 4 or 5 years, particularly for people with a psychiatric history (including suicide attempts) and for people who receive little family support.³⁴ Unemployment, which may produce or exacerbate psychiatric illness or may result from psychiatric illness,³⁴ increases the likelihood of suicide and accounts for as many as one-third to one-half of completed suicides.^43,59 This risk may be particularly elevated among men.³⁴ Financial and legal difficulties also increase the risk for suicide.^12,35,93

The presence of one or more firearms in the home appears to increase the risk of suicide independently for both genders and all age-groups, even when other risk factors, such as depression and alcohol abuse, are taken into account.^6,92,94 For example, adolescents with a gun in the household have suicide rates between 4 and 10 times higher than other adolescents.^23,95

Past and Present Suicidality

A history of suicide attempts is one of the most powerful risk factors for completed and attempted suicide.^12,96 As many as 10% to 20% of people with prior suicide attempts complete suicide.^10,17,97 The risk for completed suicide following an attempted suicide is almost 100 times that of the general population in the year following the attempt; it then declines but remains elevated throughout the next 8 years.³⁴ People with prior suicide attempts are also at greater risk for subsequent attempts and have been found to account for approximately 50% of serious overdoses.⁹⁸ The clinical use of past suicide attempts as a predictive risk factor may be limited in the elderly because the elderly make fewer attempts for each completed suicide.^19–2159

The lethality of past suicide attempts slightly increases the risk for completed suicide,³⁴ especially among women with psychiatric illness.⁴⁰ The dangerousness of an attempt, however, may be more predictive of the risk for suicide in those individuals with significant intent to suicide and a realization of the potential lethality of their actions.⁹⁹

The communication of present suicidal ideation and intent must be carefully evaluated as a risk factor for completed and attempted suicide. As many as 80% of people who complete suicide communicate their intent either directly or indirectly.⁵⁹ Death or suicide may be discussed, new wills or life insurance policies may be written, valued possessions may be given away, or uncharacteristic and destructive behaviors may arise.⁵⁹

People who intend to commit suicide may, however, be less likely to communicate their intent to their health care providers than they are to close family and friends.⁴⁶ Although 50% of people who commit suicide have consulted a physician in the month before their death, only 60% of them communicated some degree of suicidal ideation or intent to their physician.^3,46 In a study of 571 cases of completed suicide who had met with their health care professional within 4 weeks of their suicide,¹⁰⁰ only 22% discussed their suicidal intent. Many investigators believe that ideation and intent may be more readily discussed with psychiatrists than with other physicians.^100,101

Hopelessness, or negative expectations about the future, is a stronger predictor of suicide risk than is depression or suicidal ideation,^102,103 and may be both a short-term and long-term predictor of completed suicide in patients with major depression.⁴⁶

Contact with Physicians

Nearly half of the people who commit suicide have contact with their primary care provider (PCP) within 1 month of committing suicide.^35,46,104 Approximately three-quarters of people who commit suicide saw a PCP in the year before the suicide.¹⁰⁴ Many of these individuals seek treatment from their PCP for somatic rather than psychiatric complaints.¹⁰⁵ Rates of psychiatric encounters in the period before completed suicides are lower than those for primary care contacts.¹⁰⁴ In the month before a completed suicide, approximately one-fifth of suicide completers obtained mental health services, and in the year before a completed suicide, approximately one in three suicide completers had contact with a mental health professional.¹⁰⁴

Neurobiology

Of all the neurotransmitters, the relationship of serotonin to suicidality has been most widely studied.¹⁶ An association between decreased cerebrospinal fluid (CSF) levels of the serotonin metabolite 5-hydroxy indole acetic acid (HIAA) and serious suicide attempts was first described in the 1970s.¹⁰⁶ Since then, evidence of an association between the serotonergic system and suicidality has continued to grow, with most subsequent studies finding decreased CSF 5-HIAA levels in individuals who attempt suicide.^107,108 There have also been reports of a blunted prolactin response to fenfluramine challenge, a marker for serotonergic dysfunction.^82,107–109 This finding is independent of underlying psychiatric diagnosis, that is, it is consistent for suicide attempters with major depression, schizophrenia, and personality disorders compared to diagnosis-matched controls without a history of attempting suicide.^107,108 Low levels of 5-HIAA are associated with more serious attempts, and are negatively correlated with the degree of injury in the most recent suicide attempt or most serious past attempt.^107,108,110 That is, higher-lethality past attempts are associated with lower CSF 5-HIAA levels. Finally, low CSF 5-HIAA has also been shown to predict future attempted and completed suicide.¹¹¹

Similarly, postmortem brainstem analysis has shown a reduction in serotonin and its metabolite 5-HIAA in suicide completers.^{29,107,112,113} This reduction in serotonin and 5-HIAA was similar for depressed, schizophrenic, personality-disordered, and alcoholic patients, showing that decreased brainstem serotonin activity correlates with completed suicide irrespective of diagnosis.^107,113 Other brainstem abnormalities associated with suicide victims are the presence of an increased number of serotonin neurons compared to controls.^16,29,114