Key Research Findings

Our effectiveness in preventing suicide ultimately depends on more fully understanding how and why suicide occurs.

What we know about the causes of suicide lags far behind our knowledge of many other life-threatening illnesses and conditions. In part, this is because the stigma surrounding suicide has limited society’s investment in suicide research. Over the last 25 years, however, we have begun to uncover and understand the complex range of factors that contribute to suicide.

Summarized below are findings from research studies that have especially contributed to our current understanding of suicide.

Mental Disorders

While nearly all mental disorders have the potential to increase the risk for suicide, studies show that the most common disorders among people who die by suicide are major depression and other mood disorders, and substance use disorders, schizophrenia and personality disorders (Bertolote & Fleischmann, 2002). Much of what is known about the relationship between those underlying mental disorders and suicide has come from “psychological autopsy” studies. These in-depth investigations rely on interviews with family, close friends, and others who were in close contact with the person who died by suicide, in order to identify factors that likely contributed to the death. Such studies have consistently found that the overwhelming majority of people who die by suicide—90% or more—had a mental disorder at the time of their deaths. Often, however, these disorders had not been recognized, diagnosed, or adequately treated. Psychological autopsy studies have also shown that about one-third of people who took their lives did not communicate their suicide intent to anyone. One of the most important conclusions from this research is the importance of teaching laypeople to recognize the symptoms of mental disorders in those they are close to, so that they can support them to get help.

There are also important implications for primary care professionals. One large analysis of 40 separate postmortem studies found that 45% of those who died by suicide had seen a primary care provider within the month before their death, and 77% had such contact within the past year (Luoma, et al., 2002). Older adults who died by suicide were even more likely to have had recent contact with a primary care provider. By contrast, only about 30% of all those who died by suicide had receivedmental healthservices during the last year of life, and only 19% in the last month. These findings suggest that suicides may be reduced if primary care providers and their staffs were better able to recognize and treat (or refer for specialty care) patients who show signs of the mental disorders that are most commonly associated with suicide.  

Among people who die by suicide, depression is more common than any other other disorder. Therefore, efforts to educate primary care providers about the diagnosis and treatment of depression are especially important. Research has shown that certain symptoms in the context of  depression raise the risk of suicide. These include intense anxiety, panic attacks, desperation, hopelessness, feeling that one is a burden, loss of interest and pleasure, and delusional thinking..

Previous Suicide Attempt

About 20% of people who die by suicide have made a prior suicide attempt, and clinical studies have confirmed that such prior attempts increase a person’s risk for subsequent suicide death. Suicide risk appears to be especially elevated during the days and weeks following hospitalization for a suicide attempt, especially in people with diagnoses of major depression, bipolar disorder, and schizophrenia (Tidemalm, et al., 2008).

The majority of people who make a suicide attempt, however, do not ultimately die by suicide. Studies that have followed suicide attempters identified in hospital emergency rooms have found that just 7–10% died by suicide over the next two decades (Jenkins, et al., 2002; Carter, et al., 2007). Data collected by the Centers for Disease Control and Prevention show clear differences in the gender and age patterns of suicide attempters and those who die by suicide. Young women, for example, are estimated to make 100 or more suicide attempts for every completed suicide, but yet they have a low rate of completed suicide. In contrast, the elderly have a suicide rate that is twice the rate among youth, but make relatively few non-fatal suicide attempts. Greater overall frailty and increased likelihood of physical illnesses contributes to the lethality of suicide attempts in older adults.    

Family History of Suicide

Research has shown that the risk for suicide can be inherited (Juel-Nielsen & Videbech, 1970; Roy, et al., 1991; Lester, 2002). Identical twins, for example, have been found to have stronger concordance for suicide than fraternal twins, even when they are raised separately. Studies of people who were adopted and subsequently died by suicide have found suicide to be more common among these individuals’ biological parents than their adopted parents. Although studies show that depression and other psychopathology also runs in families, the heritability of suicide appears to exist even independent from inherited depression. Exposure to completed and attempted suicide in the family has also been found to increase suicide risk among  family members by providing a “social model” of self-harm behavior (de Leo & Heller, 2008).  

While these studies indicate that a family history of suicide can be a risk factor for suicide, they do not suggest that a suicide in the family automatically heightens suicide risk for all family members. Family history is one among many factors that can contribute to a person’s vulnerability or resilience. As with other genetically-linked illnesses and conditions, awareness of possible risk and attention to early signs of problems in oneself or a loved one can be protective if it leads those who have lost a relative to suicide to seek timely treatment or intervention.

Medical Conditions and Pain

Patients with serious medical conditions such as cancer, HIV, lupus, and traumatic brain injury may be at increased risk for suicide. This is primarily due to psychological states such as hopelessness, helplessness, and desire for control over death. Chronic pain, insomnia and adverse effects of medications have also been cited as contributing factors. These findings point to a critical need for increased screening for mental disorders and suicidal ideation and behavior in general medical settings.

Relationship Between Environmental Stressors, Mental Disorders and Suicide Risk

One of the major challenges of suicide research is determining how mental disorders and environmental stressors interact to create a pathway to suicide. Recent research on bullying has provided important new insights into the links between environmental stressors, mental disorders and suicide risk.

Much of the current discourse on bullying and suicide posits a direct causal link between the two. Challenging this assumption, an important recent study that followed high school students for several years after graduation found that exposure to bullying had relatively few long term negative outcomes for the majority of youth. The only subgroup that showed suicidal ideation and behavior in post-high school follow-up was youth who had symptoms of depression at the time they were bullied. Bullied youth who did not have co-existing depression had significantly lower risk for later mental health problems (Klomek, et al., 2011).

 Another recent long term study links exposure to prolonged bullying to the development of serious mental disorders in later life. This research, which followed a large sample of youth and their caregivers from childhood to early adulthood, found that those who were bullied through childhood and adolescence had high rates of depression and anxiety disorders in early adulthood. Those with histories of being both victims and bullies had the most adverse outcomes as young adults, with even higher rates of mood and anxiety disorders. In addition, nearly 25% of this group reported suicidal ideation or behavior as an adult. Those who were bullies but not victims showed low levels of depression or anxiety and markedly elevated rates of antisocial personality disorder (Copeland, et al., 2013).

It is important to note that existing research on bullying has looked at the outcome of attempted rather than completed suicide. However, the finding that bullying is most likely to precipitate suicidal thinking and suicide attempts in youth who are already depressed, or who have prolonged involvement as both victims and bullies, points to the role of individual vulnerability in determining the impact of environmental stressors.

Suicide Contagion

That imitative behavior (“contagion”) plays a role in suicide has long been observed. Recent studies have concluded that media coverage of suicide is connected to the increase—or decrease—in subsequent suicides, particularly among adolescents (Sisask & Värnik, 2012). High volume, prominent, repetitive coverage that glorifies, sensationalizes or romanticizes suicide has been found to be associated with an increase in suicides (Bohanna and Wang, 2012). There is also evidence that when coverage includes detailed description of specific means used, the use of that method may increase in the population as a whole (Yip, et al., 2012).

In recent years, the internet has become a particular concern because of its reach and potential to communicate information about notorious suicides and those that occur among celebrities. However, when media follows appropriate reporting recommendations, studies show that the risk of suicide contagion can be decreased (Bohanna and Wang, 2012).

Access to Lethal Methods of Suicide

There is strong evidence that the availability and use of different methods of suicide impacts suicide rates among different groups in the population and different geographical areas of the world. In the U.S., the most common method of suicide is firearms, used in 51% of all suicides. Currently, firearms are involved in 56% of male suicides and 30% of female suicides. Among U.S. women, the most common suicide method involves poisonous substances, especially overdoses of medications. Poisoning accounts for 37% of female suicides, compared to only 12% of male suicides. Hanging or other means of suffocation are used in about 25% of both male and female suicides. The difference in death rates among the most common suicide methods estimated at 80–90% for firearms and 1.5–4% for overdoses—helps to account for the roughly 4: 1 ratio of male-to-female suicides (Yip, et al., 2012). The greater availability of firearms in rural parts of the country also contributes to higher suicide rates in the more rural Western states.

Studies have shown that many suicide attempts are unplanned and occur during an acute period of ambivalence (Bohanna & Wang, 2012). Therefore, restricting access to lethal methods is a key suicide prevention strategy.

Biological Factors

Postmortem studies of the brains of people who have died by suicide have shown a number of visible differences in the brains of people who died by suicide, compare to those who died from other causes, suicide is a result of a disease of the brain (Mann & Currier, 2012). The brain systems that have been most frequently studied as factors in suicide are the serotonergic system, adrenergic system and the Hypothalamic-Pituitary Axis (HPA), which relate to mood, thinking and stress response, respectively. This research has also identified neurobiological impairments related to depression and other underlying mental disorders, as well as to acute or prolonged stressors. One of the key challenges of neurobiological studies is determining the abnormalities in genes, brain structures or brain function that differentiate depressed people who died by suicide from depressed people who died by other causes.


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Bohanna I. & Wang X. (2012). Media guidelines for the responsible reporting of suicide: a review of effectiveness. Crisis: Journal of Crisis Intervention & Suicide, 33(4): 190–8

Carter G.L., Child C., Page A., Clover K., Taylor R. (2007). Modifiable risk factors for attempted suicide in Australian clinical and community samples. Suicide and Life-Threatening Behavior, 37: 671–80.

Copeland W.E., Angold A., Costello E.J. Egger H. (2013). Prevalence, comorbidity, and correlates of DSM-5 proposed disruptive mood dysregulation disorder. American Journal of Psychiatry, 170: 173–9.

de Leo D. & Heller T. (2008). Social modeling in the transmission of suicidality. Crisis: Journal of Crisis Intervention & Suicide, 29(1): 11–9.

Jenkins G.R., Hale R., Papanastassiou M., Crawford M.J., Tyrer P. (2002). Suicide rate 22 years after parasuicide: cohort study. BMJ, 325(7373): 1155.

Juel-Nielsen N. & Videbech T. (1970). A twin study of suicide. Acta Geneticae Medicae et Gemellologiae, 19(1): 307–10.

Klomek A.B., et al. (2011). High school bullying as a risk for later depression and suicidality. Suicide and Life-Threatening Behavior, 41(5): 501–16.

Lester D. (2002). Twin studies of suicidal behavior. Archives of Suicide Research, 6: 338–389.

Luoma J.B., Martin C.E., Pearson J.L. (2002). Contact with mental health and primary care providers before suicide: a review of the evidence. American Journal of Psychiatry, 159(6): 909–16.

Mann J.J. & Currier D. (2012). Neurobiology of Suicidal Behavior. In R.I. Simon & R.E. Hales (Eds.), The American Psychiatric Publishing Textbook of Suicide Assessment and Management (481–500).

Roy A., Segal N.L., Centerwall B.S. & Robinette C.D. (1991). Suicide in twins. Archives of General Psychiatry, 48(1): 29–32.

Sisask M. & Värnik A. (2012). Media roles in suicide prevention: a systematic review. International Journal of Environmental Research and Public Health, 9(1): 123–38.

Tidemalm D., Langstrom N., Lichtenstein P., Runeson B. (2008). Risk of suicide after suicide attempt according to coexisting psychiatric disorder: Swedish cohort study with long term follow-up. BMJ: 337, a2205.

Yip P.S., Caine E., Yousuf S., Chang S.S., Wu K.C., Chen Y.Y. (2012). Means restriction for suicide prevention. Lancet, 379(9834): 2393–9.