In 2019, there were 47,511 reported suicide deaths in the United States, making it the 10th leading overall cause of mortality [1]. Every day, approximately 130 Americans take their own life, and one person dies by suicide every 11.2 minutes. An estimated 90% of persons who die by suicide have a diagnosable psychiatric disorder at the time of death, although only 46% have a documented diagnosis [2,3].

Suicide rates vary according to race, ethnicity, sex, and many other factors, including age [8]. In almost every country, suicide is predominated by male victims, with the exception of China, which is the only country in which the female suicide rate (14.8 per 100,000) exceeds the male rate (13 per 100,000) [9]. In the United States, the number of deaths by suicide is nearly four times greater among men (37,256) than among women (10,255). Overall, suicide accounts for 1.7% of all deaths in the United States and a death rate of 13.9 per 100,000 [1].

Although official national statistics are not compiled on attempted suicide (i.e., nonfatal actions), it is estimated that 1.2 million adults (18 years of age and older) attempt suicide each year [13]. Overall, there are roughly 25 attempts for every death by suicide; this ratio changes to 100 to 200:1 for the young and 4:1 for the elderly [13,16]. The risk of attempted (nonfatal) suicide is greatest among women and the young, and the ratio of female-to-male nonfatal suicide attempts is 2 to 3:1 [2,10,13].

Alterations in several neurobiologic systems are associated with suicidal behavior, most prominently hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, serotonergic system dysfunction, and excessive activity of the noradrenergic system. While the first and the last system appear to be involved in the response to stressful events, serotonergic dysfunction is thought to be trait-dependent and associated with disturbances in the regulation of anxiety, impulsivity, and aggression [27,28]. Altered functioning of these systems may stem from both genetic and developmental causes. Exposure to extreme or chronic stress during childhood has developmental consequences on these systems that persist into adulthood. Genetic differences may also contribute to alterations in the functioning of these neurobiologic systems, and the interactive effect of adverse childhood experiences, such as physical abuse, sexual abuse, or caregiver abandonment, with genetic vulnerability is increasingly believed to play a role in suicidal behavior [27,29].

A woman takes her own life every 51.25 minutes in the United States [1]. Suicide is more common among women who are single, recently separated, divorced, or widowed, and the suicide rates for women peak between the ages of 45 to 64 years. Precipitating life events for women who attempt suicide often involve interpersonal losses or crises in significant social or family relationships. As noted, more women attempt suicide than men, and there is a 2 to 3:1 ratio of women versus men with a history of attempted suicide. The higher rates of attempted suicide among women are likely due to the higher rates of mood disorders such as major depression, persistent depressive disorder (dysthymia), and seasonal affective disorder. Factors that may contribute to the lower rates of suicide deaths in women relative to men include stronger social supports, feeling that their relationships are a deterrent to suicide, differences in preferred suicide method, and greater willingness to seek psychiatric and medical intervention [2,13].

Most adolescent suicides occur at home after school hours. Adolescent nonfatal suicide attempters are typically girls who ingest pills, while those who die by suicide are typically boys who die from gunshot wounds. Intentional self-harm should be considered serious and in need of further evaluation because not all adolescent attempters admit their intent. Most adolescent suicide attempts are triggered by interpersonal conflicts and are motivated by the desire to change the behavior or attitude of others. Repeat attempters may use this behavior as a coping mechanism for stress and tend to exhibit more chronic symptomatology, worse coping histories, and higher rates of suicidal and substance abuse behaviors in their family histories [13]. The presence of multiple emotional, behavioral, and/or cognitive problems may be a more important predictor of suicide behavior risk than a specific type of problem (e.g., an addictive behavior or an emotional problem) [13,33]. The presence of acne is associated with social and psychologic problems, and certain acne medications have been linked with an increased risk of suicidal ideation [36].

The elderly account for roughly 19.3% of suicides but only 16% of the population [13]. Suicide rates rise with age for men, especially after 65 years of age, and the suicide rate in elderly men is 5 times that of same-aged women; more than 85% of elderly suicides are among men [13,35]. The overall rate of elderly suicide is nearly 20 per 100,000. However, the rate is 40 per 100,000 among elderly White men and 51.8 per 100,000 among White men older than 85 years of age, a rate that is almost 2 times the rate for men of all ages. In contrast, the suicide rate of women declines after 60 years of age [13,35].

Although undiagnosed and/or untreated depression is the primary cause of suicide in the elderly, suicide completion is rarely preceded by only one factor. Risk factors for suicide in this population include a previous suicide attempt; mental illness; physical illness or uncontrollable pain; fear of a prolonged illness; major changes in social roles, such as retirement; loneliness and social isolation (especially in older men who have recently lost a loved one); and access to lethal means, such as firearms in the home [13].

LGBT+ youth generally have more risk factors, more severe risk factors, and fewer protective factors, such as family support and safe schools, than heterosexual youth. There are also risks unique to this population related to sexual orientation, such as disclosure to family or friends [13]. The impact of stigma and discrimination against LGBT+ individuals is enormous and is directly tied to risk factors for suicide such as isolation, alienation and rejection from family, and lack of access to culturally competent care [43]. Family connectedness, perceived caring from other adults, and feeling safe at school were reported as significant protective factors in a survey of 6th-, 9th-, and 12th-grade LGBT+ students [37,38]. It has also been noted that LGBT+ adults have a two-fold excess risk of suicide than their heterosexual counterparts [37].

Although the true incidence of suicide among military service members and veterans is difficult to estimate due to the lack of national suicide surveillance data, the U.S. Department of Veterans Affairs (VA) estimates that 18% of all deaths from suicide in the United States are in military war veterans [79]. Despite preventive measures taken by the military, the number of suicides in this population continues to increase [52,54,56,79]. Although the majority of military suicides occur among young men shortly after their discharge from military service, military women 18 to 35 years of age commit suicide nearly three times more frequently than civilian women of the same age group [57,58]. Servicewomen, in particular, experience high rates of interpersonal violence, including childhood abuse, intimate partner violence, and sexual trauma during adulthood (e.g., military sexual assault) [123].

Several protective factors against suicide behavior have been identified [5,62]. These include:

In addition to risk factors specific to special populations, there are many general risk factors common among most populations. General biopsychosocial risk factors include [2,5,62]:

At least 90% of people who die by suicide have diagnosable psychiatric illness [2,3]. The psychiatric conditions with the greatest association with suicidal behavior are depression, bipolar disorder, substance abuse, schizophrenia, and personality disorders.

Major depression is the psychiatric diagnosis most commonly associated with suicide. The risk of suicide in persons with major depression is roughly 20 times that of the general population [13]. About 30% of all patients with major depression attempt suicide, half of whom ultimately take their own lives [63]. More than 60% of persons who die by suicide are clinically depressed at the time of their deaths, although this climbs to 75% when patients with comorbid depression and alcohol use disorder are added. Seven of every 100 men and 1 of every 100 women diagnosed with depression will die by suicide [13].

Alcohol and drug abuse are second only to depression and other mood disorders as conditions most associated with suicide. Substance use disorders and disordered mood are often comorbid. The suicide risk among patients with alcohol use disorder is 50% to 70% higher than the general population. Alcohol abuse is a factor in roughly 30% of suicides, and about 7% of persons with alcohol dependence die by suicide [2,13,68].

In 2011, an estimated 228,366 emergency department admissions were made for alcohol- or drug-related suicide attempts. Almost all (94.7%) involved either a prescription drug or an over-the-counter medication [69]. Approximately 64.4% involved multiple drugs, and 29% involved alcohol [69].

Illnesses affecting the brain and CNS have a greater effect on suicide risk compared with other medical conditions. These conditions include epilepsy, AIDS, Huntington disease, traumatic head injury, and cerebrovascular accidents. In contrast, cancer and other potentially fatal conditions carry a more modest suicide risk [71].

Divorced, widowed, and single people have a higher suicide risk. Marriage appears to be protective for men, but not so for women. Marital separation also increases the risk of suicide [59,60].

Certain occupational groups, such as veterinary surgeons, pharmacists, dentists, farmers, and medical practitioners, have higher rates of suicide. Although obvious explanations are lacking, access to lethal means, work pressure, social isolation, and financial difficulties may account for the heightened risk [59,60].

Unemployment and suicide are also correlated, although the nature of the association is complex. Poverty, social deprivation, domestic difficulties, and hopelessness likely mediate the effect of unemployment, but persons with psychiatric illness and personality disorders are also more likely to be unemployed. Recent job loss is a greater risk factor than long-term unemployment.

Approximately 20% of people who kill themselves had made a previous attempt, making previous serious suicide attempts a very high risk factor for future attempts [2].

Inmates at highest risk of suicide include young men, the mentally ill, the socially disenfranchised and socially isolated, substance abusers, previous suicide attempters, and juveniles placed in adult correctional facilities. Factors that increase the likelihood of suicidal behavior include the psychologic impact of arrest and incarceration; the stresses of prison life, including physical and sexual predation and assault from other inmates; and the absence of formal policies regarding managing suicidal patients, staff training, or access to mental health care [44,72].

Veterans and military members often possess many risk factors for attempting or completing suicide. This includes combat exposure (particularly deployment to a combat theater and/or adverse deployment experiences), combat wounds, post-traumatic stress disorder (PTSD) and other mental health problems, comorbid major depression, traumatic brain injury, poor social support, feelings of not belonging or of being a burden to others or society, acquired ability to inflict lethal self-injury, and access to lethal means [52,58,81,82,83]. There is conflicting evidence of the role of PTSD in suicide risk, with some studies finding PTSD diagnosis to be protective while others indicated it increased risk. Other possible risk factors include [79,123]:

Most people who are suicidal exhibit warning signs, whether or not they are in an acute suicide crisis. These warning signs should be taken seriously and include observable signs of serious depression, such as unrelenting low mood, pessimism, hopelessness, desperation, anxiety, psychic pain, and inner tension; withdrawal from friends and/or social activities; sleep problems; and loss of interest in personal appearance, hobbies, work, and/or school [2,13]. Other signs include:

Intentional self-harm is behavior related to, but distinct from, suicide behavior and includes suicide attempts and nonsuicidal self-injurious behaviors, such as burning, cutting, and hair pulling, that does not have fatal intent [85]. Self-injurious behavior falls into three categories [85]:

In the United States in 2019, use of a firearm was the cause of death in 50.4% of suicides and is the number one means among all individuals 15 years of age and older. Gun use accounts for 47% of all suicide deaths in individuals 15 to 24 years of age, reaching a low of 42.1% in those 35 to 44 years of age, and increasing to 51.8% in those 55 to 64 years of age. Firearm use for suicide completion is extremely high among the elderly, with individuals 75 to 84 and 85 years of age and older having the highest rates, at 75.4% and 76.6%, respectively. Gun use is also the most common suicide method among youth, accounting for 31.5% of all suicide deaths [1,78].

The most common method of suicide death among women in all age groups from 2001 to 2019 was poisoning (35.5%); however, in 2018, firearms surpassed poisoning for the first time since 2000 among female victims [15,78]. Although intentional overdose is the most common method for suicide attempts in women, it is much less likely to result in death. Many over-the-counter medications, prescription drugs, dietary supplements/herbal medications, or illicit drugs may be used to attempt suicide. Ibuprofen is a popular over-the-counter analgesic and a common drug of choice in intentional overdoses. There were more than 12,490 intentional overdose ingestions of ibuprofen reported by U.S. poison control centers in 2018, resulting in one death [89]. Opioid analgesics result in many deaths due to intentional overdose. In one study, researchers found that the percentage of individuals who died by suicide and had opioids in their system more than doubled, from 8.8% to 17.7%, between 2006 and 2017 [45].

Healthcare providers may encounter a patient they suspect is suicidal. This suspicion may be prompted by the presence of one or more of the risk factors for suicide described previously, patient history, a statement expressed by the patient, or by their intuition. This scenario may present a dilemma of how to proceed. Although some healthcare professionals are uncomfortable with suicidal patients, it is essential not to ignore or deny the suspicion of suicide risk. The first and most immediate step is to allocate adequate time to the patient, even though many others may be scheduled. Showing a willingness to help begins the process of establishing a positive rapport with the patient. Closed-ended and direct questions at the beginning of the interview are not very helpful; instead, use open-ended questions such as, "You look very upset; tell me more about it." Listening with empathy is in itself a major step in reducing the level of suicidal despair and overall distress [59,60]. It is helpful to lead into the topic gradually with a sequence of useful questions, such as [59,60]:

In general, the more an individual has thought about suicide, made specific plans, and intends to act on those plans, the greater the suicide risk. Thus, as part of the assessment of suicide risk it is essential to inquire specifically about the patient's suicidal thoughts, plans, behaviors, and intent. Such questions may often flow naturally from discussion of the patient's current situation, but in other cases they should be explicitly asked [62].

Persons with a mental disorder who are managed appropriately according to evidence-based guidelines and do not report suicidal thoughts are outside the scope of the classification of risk for suicide. Patients who at some point in the past have reported thoughts about death or suicide but currently do not have any of these symptoms are not considered to be at acute risk of suicide. There is no indication to consult with behavioral health specialty in these cases, and the patients should be followed in routine care, continue to receive treatment for their disorder, and be re-evaluated periodically for thoughts and ideation. Patients at no elevated acute risk should be followed in routine care with treatment of their underlying condition and evaluated periodically for ideation or suicidal thoughts. Patients for whom the risk remains undetermined (i.e., no collaboration of the patient or provider concerns about the patients despite denial of risk) should be evaluated by a behavioral health practitioner [79].

The opportunity for an emotionally disturbed patient with vague suicidal ideation to vent his or her thoughts and feelings to an understanding health or mental health provider may bring a degree of relief such that no further intervention is needed. However, in all cases the encouragement of further contact and follow-up should be conveyed to the patient, especially when inadequate social support is present. Independent of the actual catalyst, most suicidal persons possess feelings of helplessness, hopelessness, and despair and a triad of three cognitive/emotional conditions [59,60]:

Abundant evidence has demonstrated that lithium reduces the rate of suicidal behavior in patients with bipolar disorder and recurrent major depression and that clozapine reduces suicidal behavior in schizophrenia [97,98,99,100,101,102]. Both drugs reduce suicide risk independently of their effect on the primary psychiatric disorder. Although the exact anti-suicide mechanism of both drugs has yet to be identified, lithium enhances serotonergic activity and clozapine is a potent 5-HT2A antagonist. Serotonergic modulation is a likely explanation of the suicide-reducing effects of both medications, because aggression levels and suicide are correlated with prefrontal cortical 5-HT2A binding [71,104,105].

Dialectical behavior therapy was originally designed to address the self-harm impulses of patients with borderline personality disorder, but it has good evidence for use in most suicidal individuals. Dialectical behavioral therapy is an adaptation of cognitive-behavioral therapy and is based on the theoretical principle that maladaptive behaviors, including self-injury, are attempts to manage intense overwhelming affect of biosocial origin. It consists of the two key elements of a behavioral, problem-solving approach blended with acceptance-based strategies and an emphasis on dialectical processes. Dialectical behavioral therapy emphasizes balancing behavioral change, problem-solving, and emotional regulation with validation, mindfulness, and acceptance of patients. Therapeutic targets are ranked in hierarchical order, with life-threatening behaviors addressed first, followed by therapy-interfering behaviors, and then behaviors that interfere with quality of life.

Depending on the level of suicide risk, referral to a mental health professional (e.g., psychologist, counselor, therapist), psychiatrist, or hospitalization may be warranted. Long-term treatment and follow-up will be required for many patients, and appropriate referral to outpatient facilities is often necessary. If the person is currently in therapy, the therapist should be called and involved in the management decision. If the patient does not have a therapeutic relationship with a mental health professional, referral to one should be made. Suicidal patients should be referred to a psychiatrist when any of the following are present: psychiatric illness; previous suicide attempt; family history of suicide, alcoholism, and/or psychiatric disorder; physical illness; or absence of social support [59,60]. After deciding to refer a patient to a mental health professional, the clinician should explain to the patient the reason for the referral and help alleviate patient anxiety over stigma and psychotropic medications. It is also important to help the patient understand that pharmacologic and psychologic therapies are both effective and to emphasize to the patient that referral does not mean "abandonment." The referring clinician should also arrange an appointment with the mental health professional, allocate time for the patient following the initial appointment with the therapist or psychiatrist, and ensure the ongoing relationship with the patient [59,60].

It is important to ensure that the patient has follow-up contact even after discharge to another provider. At the point of discharge, information should be provided on crisis options (referred to as "crisis cards") and free, universally available help, such as hotlines. There is evidence that follow-up outreach in the form of letters or postcards expressing care and concern and continuing for up to three years may be helpful in suicide prevention [75]. These letters should generally be non-demanding, allowing the opportunity but not the requirement for patients to respond.

The VA/DoD has made the following recommendations when creating a treatment plan for veterans and active service members [79]:

Understanding the interactive relationship between risk and protective factors in suicidal behavior and how this interaction can be modified forms the basis of suicide prevention [5,106]. The characteristics shared by effective suicide prevention programs include clear identification of the intended population, definition of desired outcomes, use of interventions known to effect a particular outcome, and use of community coordination and organization to achieve an objective. Prevention efforts are based on a clear plan with goals, objectives, and implementation steps [5,45].

On a systems level, the stigma surrounding mental illness, substance use disorders, and suicide has contributed to inadequate funding for preventive services and inadequate insurance reimbursement for treatments. Substance use and mental health conditions, including those associated with suicide, will remain undertreated and services tailored to persons in crisis will remain limited as long as stigma persists, resulting in an unnecessarily high rate of suicidal behavior and suicide [5]. Additionally, the stigma associated with mental illness and substance abuse has led to separate systems for physical health and mental health care, a consequence being that preventive and treatment services for mental illness and substance abuse are much less available than for other health problems. This separation has also led to bureaucratic and institutional barriers between the two systems that impede and complicate access to care and service implementation [5].