Suicide (
Latin suicidium, from
sui caedere, "to kill oneself") is the act of intentionally causing one's own
death. Suicide is often committed out of
despair, the cause of which is frequently attributed to a
mental disorder such as
depression,
bipolar disorder,
schizophrenia,
borderline personality disorder,
[1] alcoholism, or
drug abuse.
[2] Stress factors such as
financial difficulties or troubles with
interpersonal relationships often play a role. Efforts to prevent suicide include limiting access to firearms, treating mental illness and drug misuse, and improving economic development.
The most commonly used method of suicide varies by country and is partly related to availability. Common methods include:
hanging,
pesticide poisoning, and firearms. Around 800,000 to a million people die by suicide every year, making it the 10th leading cause of death worldwide.
[2][3] Rates are higher in men than in women, with males three to four times more likely to kill themselves than females.
[4] There are an estimated 10 to 20 million
non-fatal attempted suicides every year.
[5] Attempts are more common in young people and females.
Definitions
Suicide, also known as completed suicide, is the "act of taking one's own life".
[8] Attempted suicide or non-fatal suicidal behavior is
self-injury with the desire to end one's life that does not result in death.
[9] Assisted suicide is when one individual helps another bring about their own death indirectly via providing either advice or the means to the end.
[10] This is in contrast to
euthanasia, where another person takes a more active role in bringing about a person's death.
[10] Suicidal ideations is thoughts of ending one's life but not taking any active efforts to do so.
[9]
Risk factors
The precipitating circumstances for suicide from 16 American states in 2008.
[11]
Factors that affect the risk of suicide include
psychiatric disorders,
drug misuse, psychological states, cultural, family and social situations, and genetics.
[12] Mental illness and substance misuse frequently co-exist.
[13] Other risk factors include having previously attempted suicide,
[14] the ready availability of a means to commit the act, a family history of suicide, or the presence of
traumatic brain injury.
[15] For example, suicide rates have been found to be greater in households with firearms than those without them.
[16] Socio-economic factors such as unemployment, poverty,
homelessness, and discrimination may trigger suicidal thoughts.
[17] About 15–40% of people leave a
suicide note.
[18] Genetics appears to account for between 38% and 55% of suicidal behaviors.
[19] War veterans have a higher risk of suicide due in part to higher rates of mental illness and physical health problems related to
war.
[20]
Mental disorders
A history of previous suicide attempts is the greatest predictor of eventual completion of suicide.
[14] Approximately 20% of suicides have had a previous attempt and of those who have attempted suicide 1% complete suicide within a year
[14] and more than 5% commit suicide after 10 years.
[25] Acts of
self-harm are not usually suicide attempts and most who self-harm are not at high risk of suicide.
[26] Some who self-harm; however, do still end their life by suicide and risk for self-harm and suicide may overlap.
[26]
In approximately 80% of completed suicides the individual has seen a physician within the year before their death,
[27] including 45% within the prior month.
[28] Approximately 25–40% of those who completed suicide had contact with mental health services in the prior year.
[21][27]
Substance use
"The Drunkard's Progress", 1846 demonstrating how alcoholism can lead to poverty, crime, and eventually suicide
Most people are under the influence of
sedative-hypnotic drugs (such as alcohol or benzodiazepines) when they commit suicide
[31] with alcoholism present in between 15% and 61% of cases.
[13] Countries that have higher rates of alcohol use and a greater density of bars generally also have higher rates of suicide
[32] with this link being primarily related to
distilled spirit use rather than total alcohol use.
[13] About 2.2–3.4% of those who have been treated for alcoholism at some point in their life die by suicide.
[32] Alcoholics who attempt suicide are usually male, older, and have tried to commit suicide in the past.
[13] Between 3 and 35% of deaths among those who use heroin are due to suicide (approximately 14 fold greater than those who do not use).
[33]
The misuse of
cocaine and
methamphetamines has a high correlation with suicide.
[13][34] In those who use cocaine the risk is greatest during the withdrawal phase.
[35] Those who used
inhalants are also at significant risk with around 20% attempting suicide at some point and more than 65% considering it.
[13] Smoking cigarettes is associated with the risk of suicide.
[36] There is little evidence as to why this association exists; however it has been hypothesized that those who are predisposed to smoking are also predisposed to suicide, that smoking causes health problems which subsequently make people want to end their life, and that smoking affects brain chemistry causing a propensity for suicide.
[36] Cannabis however does not appear to independently increase the risk.
[13]
Problem gambling
Problem gambling is associated with increased
suicidal ideation and attempts compared to the general population.
[37] Between 12 and 24% pathological gamblers attempt suicide.
[38] The rate of suicide among their spouses is three times greater than that of the general population.
[38] Other factors that increase the risk in problem gamblers include mental illness, alcohol and drug misuse.
[39]
Medical conditions
There is an association between suicidality and physical health problems including:
[25] chronic pain,
[40] traumatic brain injury,
[41] cancer,
[42] those on
hemodialysis,
HIV,
systemic lupus erythematosus, among others.
[25] The diagnosis of cancer approximately doubles the subsequent risk of suicide.
[42] The prevalence of increased suicidality persisted after adjusting for depressive illness and alcohol abuse. In people with more than one medical condition the risk was particularly high. In Japan health problems are listed as the primary justification for suicide.
[43]
Psychosocial states
A number of psychological states increase the risk of suicide including:
hopelessness, loss of pleasure in life,
depression and anxiousness.
[22] A poor ability to solve problems, the loss of abilities one used to have, and poor impulse control also play a role.
[22][46] In older adults the perception of being a burden to others is important.
[47]
Recent life stresses such as a loss of a family member or friend, loss of a job, or social isolation (such as living alone) increases the risk.
[22] Those who have never married are also at greater risk.
[14] Being religious may reduce one's risk of suicide.
[48] This has been attributed to the negative stance many religions take against suicide and to the greater connectedness religion may give.
[48] Muslims, among religious people, appear to have a lower rate.
[49]
An
evolutionary explanation for suicide is that it may improve
inclusive fitness. This may occur if the person committing suicide cannot have more children and takes resources away from relatives by staying alive. An objection is that deaths by healthy adolescents likely does not increase inclusive fitness.
Adaptation to a very different ancestral environment may be maladaptive in the current one.
[46][53]
Poverty is associated with the risk of suicide.
[54] Increasing relative poverty compared to those around a person increases suicide risk.
[55] Over 200,000 farmers in
India have committed
suicide since 1997 partly due to issues of
debt.
[56] In China suicide is three times as likely in rural regions as urban ones partly it is believed due to financial difficulties in this area of the country.
[57]
Media
The media, which includes the Internet, plays an important role.
[12] How it presents depiction of suicide may have a negative effect, with high volume, prominent, repetitive coverage glorifying or romanticizing suicide having the most impact.
[58] When detailed descriptions of how to commit suicide by a specific means is portrayed, this method of suicide may increase in the population as a whole.
[59]
This trigger of 'suicide contagion' or
copycat suicide is known as the
Werther effect, named after the protagonist in
Goethe's
The Sorrows of Young Werther, who committed suicide.
[60] This risk is greater in adolescents who may romanticize death.
[61] It appears that while news media has a significant effect, that of the entertainment media is equivocal.
[62] The opposite of the Werther effect is the proposed Papageno effect, in which coverage of effective coping mechanisms may have a protective effect. The term is based upon a character in
Mozart's opera
The Magic Flute, who (fearing the loss of a loved one) had planned to commit suicide until his friends helped him out.
[60] When media follows appropriate reporting guidelines the risk of suicides can be decreased.
[58] Getting buy-in from industry, however, can be difficult, especially in the long term.
[58]
Rational
Rational suicide is the reasoned taking of one's own life,
[63] although some feel that suicide is never logical.
[63] The act of taking one's life for the benefit of others is known as
altruistic suicide.
[64] An example of this is an elder ending his or her life to leave greater amounts of food for the younger people in the community.
[64] Suicide in some Eskimo cultures has been seen as an act of respect, courage, or wisdom.
[65]
A
suicide attack is a political action where an attacker carries out violence against others which they understand will result in their own death.
[66] Some suicide bombers are motivated by a desire to obtain
martyrdoms.
[20] Kamikaze missions were carried out as a duty to a higher cause or moral obligation.
[65]Murder–suicide is an act of
homicide followed within a week by suicide of the person who carried out the act.
[67] Mass suicides are often performed under
social pressure where members give up autonomy to a leader.
[68] Mass suicides can take place with as few as two people, often referred to as a
suicide pact.
[69]
In extenuating situations where continuing to live would be intolerable, some people use suicide as a means of escape.
[70] Some inmates in
Nazi concentration camps are known to have killed themselves by deliberately touching the electrified fences.
[71]
Methods
Case fatality rate by suicide method in the United States.
[16]
The leading method of suicide varies between countries. The leading methods in different regions include
hanging,
pesticide poisoning, and
firearms.
[72] These differences are believed to be in part due to availability of the different methods.
[59] A review of 56 countries found that hanging was the most common method in most of the countries,
[73]accounting for 53% of the male suicides and 39% of the female suicides.
[74]
Worldwide 30% of suicides are from pesticides. The use of this method however varies markedly from 4% in Europe to more than 50% in the Pacific region.
[75] It is also common in
Latin America due to easy access within the farming populations.
[59] In many countries, drug overdoses account for approximately 60% of suicides among women and 30% among men.
[76] Many are unplanned and occur during an acute period of ambivalence.
[59] The death rate varies by method: firearms 80-90%, drowning 65-80%, hanging 60-85%, car exhaust 40-60%, jumping 35-60%,
charcoal burning 40-50%, pesticides 6-75%, medication overdose 1.5-4%.
[59] The most common attempted methods of suicide differ from the most common successful methods with up to 85% of attempts via drug overdose in the developed world.
[25]
In United States, 57% of suicides involve the use of firearms with this method being somewhat more common in men than women.
[14] The next most common cause was hanging in males and self poisoning in females.
[14] Together these methods comprised about 40% of U.S. suicides.
[77] In Switzerland, where nearly everyone owns a firearm, the greatest number of suicides are by hanging.
[78] Jumping to one's death is common in both
Hong Kong and
Singapore at 50% and 80% respectively.
[59] In China the consumption of pesticides is the most common method.
[79] In Japan self disembowelment known as
seppuku or hara-kiri still occurs
[79] however hanging is the most common.
[80]
Pathophysiology
There is no known unifying underlying
pathophysiology for either suicide or depression.
[14] It is however believed to result from an interplay of behavioral, socio-environmental and psychiatric factors.
[59]
Prevention
Suicide prevention is a term used for the collective efforts to reduce the incidence of suicide through preventive measures. Reducing access to certain methods, such as firearms or toxins reduces the risk.
[59][87] Other measures include reducing access to charcoal and barriers on bridges and subway platforms.
[59][88] Treatment of drug and alcohol addiction, depression, and those who have attempted suicide in the past may also be effective.
[87] Some have proposed reducing access to alcohol as a preventative strategy (such as reducing the number of bars).
[13] Although
crisis hotlines are common there is little evidence to support or refute their effectiveness.
[89][90] In young adults who have recently thought about suicide,
cognitive behavioral therapy appears to improve outcomes.
[91] Economic development through its ability to reduce poverty may be able to decrease suicide rates.
[54] Efforts to increase social connection especially in elderly males may be effective.
[92] The
World Suicide Prevention Day is observed annually on September 10 with the support of the
International Association for Suicide Prevention and the
World Health Organization.
[93]
Screening
There is little data on the effects of screening the general population on the ultimate rate of suicide.
[94] As there is a high rate of people who test positive via these tools that are not at risk of suicide, there are concerns that screening may significantly increase mental health care resource utilization.
[95] Assessing those at high risk however is recommended.
[14] Asking about suicidality does not appear to increase the risk.
[14]
Mental illness
In those with mental health problems a number of treatments may reduce the risk of suicide. Those who are actively suicidal may be admitted to psychiatric care either voluntarily or involuntarily.
[14] Possessions that may be used to harm oneself are typically removed.
[25] Some clinicians get patients to sign
suicide prevention contracts where they agree to not harm themselves if released.
[14] Evidence however does not support a significant effect from this practice.
[14] If a person is at low risk, out-
patient mental health treatment may be arranged.
[25] Short-term hospitalization has not been found to be more effective than community care for improving outcomes in those with
borderline personality disorder who are chronically suicidal.
[96][97]
There is controversy around the benefit versus harm of
antidepressants.
[12] In young persons, the newer antidepressants such as
SSRIs appear to increase the risk of suicidality from 25 per 1000 to 40 per 1000.
[101] In older persons however they might decrease the risk.
[14] Lithium appears effective at lowering the risk in those with bipolar disorder and unipolar depression to nearly the same levels as the general population.
[102][103]
Epidemiology
Deaths by self-inflicted injuries per 100,000 inhabitants in 2004.
[104]
unknown
<3
3–6
6–9
9–12
12–15
15–18
|
18–21
21–24
24–27
27–30
30–33
>33
|
Approximately 0.5% to 1.4% of people die by suicide.
[3][14] Globally, as of 2008/2009, suicide is the tenth leading cause of death
[2] with about 800,000 to one million people dying annually, giving a
mortality rate of 11.6 per 100,000 persons per year.
[3] Rates of suicide have increased by 60% from the 1960s to 2012,
[87] with these increases seen primarily in the
developing world.
[2] For every suicide that results in death there are between 10 and 40 attempted suicides.
[14]
Suicide rates differ significantly between countries and over time.
[3] As a percentage of deaths in 2008 it was: Africa 0.5%, South-East Asia 1.9% Americas 1.2% and Europe 1.4%.
[3] Rates per 100,000 where: Australia 8.6, Canada 11.1, China 12.7, India 23.2, United Kingdom 7.6, United States 11.4.
[105] It is ranked as the 10th leading
cause of death in the United States in 2009 at about 36,000 cases a year,
[106] with about 650,000 people seen in emergency departments yearly due to attempting suicide.
[14] The country's rate among men in their 50's rose by nearly half in the decade 1999–2010.
[107] Lithuania, Japan and Hungary have the highest rates.
[3] The countries with the greatest absolute numbers of suicides are China and India accounting for over half the total.
[3] In China suicide is the 5th leading cause of death.
[108]
Gender
Suicide rate per 100,000 males (left) and female (right) (data from 1978–2008).
|
|
5.8–8.5
8.5–12
12–19
19–22.5
|
22.5–26
26–29.5
29.5–33
33–36.5
|
|
In the Western world, males die three to four times more often by means of suicide than do females, although females attempt suicide four times more often.
[3][14] This has been attributed to males using more lethal means to end their lives.
[109] This difference is even more pronounced in those over the age of 65 with tenfold more males committing suicide than females.
[109] China has one of the highest female suicide rates in the world and is the only country where it is higher than that of men (ratio of 0.9).
[3][108] In the
Eastern Mediterranean suicide rates are nearly equivalent between males and females.
[3] For women the highest rate of suicide is found in
South Korea at 22 per 100,000, with high rates in South-East Asia and the Western Pacific generally.
[3]
Age
In many countries the rate of suicide is highest in the middle-aged
[110] or elderly.
[59] The absolute number of suicides however is greatest in those between 15 and 29 years old due to the number of people in this age group.
[3] In the United States it is greatest in
caucasian men older than 80 years, even though younger people more frequently attempt suicide.
[14] It is the second most common cause of death in
adolescents[12] and in young males is second only to accidental death.
[110] In young males in the developed world it is the cause of nearly 30% of mortality.
[110] In the developing world rates are similar, but it makes up a smaller proportion of overall deaths due to higher rates of death from other types of
trauma.
[110] In South-East Asia in contrast to other areas of the world, deaths from suicide occur at a greater rate in young females than elderly females.
[3]
History
In
ancient Athens, a person who committed suicide without the approval of the state was denied the honours of a normal burial. The person would be buried alone, on the outskirts of the city, without a headstone or marker,
[111] however, it was deemed to be an acceptable method to deal with military defeat.
[112] In Ancient Rome, while suicide was initially permitted, it was later deemed a crime against the state due to its economic costs.
[113]
Suicide came to be regarded as a sin in Christian Europe and was condemned at the
Council of Arles in 452 as the work of the Devil. In the
Middle Ages, the Church had drawn-out discussions on the edge where the search for
martyrdom was suicidal, as in the case of
martyrs of Córdoba. Despite these disputes and occasional official rulings, Catholic doctrine was not entirely settled on the subject of suicide until the later 17th century. A criminal ordinance issued by
Louis XIV of France in 1670 was extremely severe, even for the times: the dead person's body was drawn through the streets, face down, and then hung or thrown on a garbage heap. Additionally, all of the person's property was confiscated.
[114][115]
Attitudes towards suicide slowly began to shift during the
Rennaissance.
John Donne's work
Biathanatos, contained one of the first modern defences of suicide bringing proof from the conduct of Biblical figures, such as
Jesus,
Samson and
Saul, and presenting arguments on grounds of reason and nature to sanction suicide in certain circumstances.
[116]
The secularisation of society that began during
The Enlightenment questioned traditional religious attitudes toward suicide and brought a more modern perspective to the issue.
David Hume denied that suicide was a crime as it affected no one and was potentially to the advantage of the individual. In his 1777
Essays on Suicide and the Immortality of the Soul he rhetorically asked, "Why should I prolong a miserable existence, because of some frivolous advantage which the public may perhaps receive from me?"
[116] A shift in public opinion at large can also be discerned;
The Times in 1786 initiated a spirited debate on the motion "Is suicide an act of courage?"
[117]
By the 19th-century, the act of suicide had shifted from being viewed as caused by
sin to being caused by
insanity in Europe.
[115] Although suicide remained illegal during this period, it increasingly became the target of satirical comment, such as the
Gilbert and Sullivan musical The Mikado that satirised the idea of executing someone who had already killed himself.
By 1879, English law began to distinguish between suicide and
homicide, although suicide still resulted in forfeiture of estate.
[118] In 1882, the deceased were permitted daylight burial in England
[119] and by the mid 20th century, suicide had become legal in much of the
western world.
Social and culture
Legislation
In most Western countries, suicide is no longer a crime,
[120] it however was in most Western European countries from the Middle Ages until at least the 1800s.
[118] Most of Muslim majority nations label it a criminal offense.
[49]
In Australia suicide is not a crime.
[121] It however is a crime to counsel,
incite, or aid and abet another in attempting to commit suicide, and the law explicitly allows any person to use "such force as may reasonably be necessary" to prevent another from committing suicide.
[122] The Northern Territory of Australia briefly had legal physician-assisted suicide from 1996 to 1997.
[123]
No country in Europe currently considers suicide or attempted suicide to be a crime.
[124] England and Wales decriminalized suicide via the
Suicide Act 1961 and the Republic of Ireland in 1993.
[124] The word "commit" was used in reference to it being illegal however many organisations have stopped it because of the negative connotation.
[125][126]
In India, suicide is illegal and surviving family may face legal difficulties.
[127] In Germany, active euthanasia is illegal and anyone present during suicide may be prosecuted for failure to render aid in an emergency.
[128] Switzerland has recently taken steps to legalize
assisted suicide for the chronically mentally ill. The high court in
Lausanne, in a 2006 ruling, granted an anonymous individual with longstanding psychiatric difficulties the right to end his own life.
[129]
In the United States, suicide is not illegal but may be associated with penalties for those who attempt it.
[124] Physician-assisted suicide is legal in the states of
Oregon[130] and Washington.
[131]
Religious views
A
Hindu widow burning herself with the corpse of her husband, 1820s.
In most forms of Christianity, suicide is considered a
sin, based mainly on the writings of influential Christian thinkers of the
Middle Ages, such as
St. Augustine and
St. Thomas Aquinas; but suicide was not considered a sin under the
Byzantine Christian
code of Justinian, for instance.
[132][133] In Catholic doctrine, the argument is based on the
commandment "Thou shalt not kill" (made applicable under the
New Covenant by Jesus in
Matthew 19:18), as well as the idea that life is a gift given by God which should not be spurned, and that suicide is against the "natural order" and thus interferes with God's master plan for the world.
[134]
However, it is believed that mental illness or grave fear of suffering diminishes the responsibility of the one completing suicide.
[135]Counter-arguments include the following: that the
sixth commandment is more accurately translated as "thou shalt not murder", not necessarily applying to the self; that God has given free will to humans; that taking one's own life no more violates God's Law than does curing a disease; and that a number of suicides by followers of God are recorded in the Bible with no dire condemnation.
[136]
Judaism focuses on the importance of valuing this life, and as such, suicide is tantamount to denying God's goodness in the world. Despite this, under extreme circumstances when there has seemed no choice but to either be killed or forced to betray their religion, Jews have committed individual suicide or
mass suicide (see
Masada,
First French persecution of the Jews, and
York Castle for examples) and as a grim reminder there is even a prayer in the Jewish liturgy for "when the knife is at the throat", for those dying "to sanctify God's Name" (see
Martyrdom). These acts have received mixed responses by Jewish authorities, regarded by some as examples of heroic martyrdom, while others state that it was wrong for them to take their own lives in anticipation of martyrdom.
[137]
Suicide is not allowed in
Islam.
[49] In
Hinduism, suicide is generally frowned upon and is considered equally sinful as murdering another in contemporary Hindu society.
Hindu Scriptures state that one who commits suicide will become part of the spirit world, wandering earth until the time one would have otherwise died, had one not committed suicide.
[138] However, Hinduism accepts a man's
right to end one's life through the non-violent practice of fasting to death, termed
Prayopavesa.
[139] But Prayopavesa is strictly restricted to people who have no desire or ambition left, and no responsibilities remaining in this life.
[139] Jainism has a similar practice named
Santhara.
Sati, or self-immolation by widows was prevalent in Hindu society during the Middle Ages.
[140]
Philosophy
A number of questions are raised within the philosophy of suicide, included what constitutes suicide, whether or not suicide can be a rational choice, and the moral permissibility of suicide.
[141] Philosophical arguments in regard to whether or not suicide can be morally acceptable range from strong opposition, (viewing suicide as unethical and immoral), through to perceptions of suicide as a
sacrosanctright for anyone (even a young and healthy person) who believes they have rationally and conscientiously come to the decision to end their own lives.
Opponents to suicide include Christian philosophers such as
Augustine of Hippo and
Thomas Aquinas,
[141] Immanuel Kant[142] and, arguably,
John Stuart Mill – Mill's focus on the importance of
liberty and
autonomy meant that he rejected choices which would prevent a person from making future autonomous decisions.
[143] Others view suicide as a legitimate matter of personal choice. Supporters of this position maintain that no one should be forced to suffer against their will, particularly from conditions such as incurable disease, mental illness, and old age that have no possibility of improvement. They reject the belief that suicide is always irrational, arguing instead that it can be a valid last resort for those enduring major pain or trauma.
[144] A stronger stance would argue that people should be allowed to autonomously choose to die regardless of whether they are suffering. Notable supporters of this
school of thought include Scottish empiricist
David Hume[141] and American bioethicist
Jacob Appel.
[129][145]
Advocacy
In this painting by Alexandre-Gabriel Decamps, the palette, pistol, and note lying on the floor suggest that the event has just taken place; an artist has taken his own life.
[146]
Advocacy of suicide has occurred in many cultures and
subcultures. The
Japanese military during World War II encouraged and glorified
kamikaze attacks, which were suicide attacks by military aviators from the Empire of Japan against Allied naval vessels in the closing stages of the Pacific theatre of World War II. Japanese society as a whole has been described as suicide "tolerant"
[147] (see
Suicide in Japan).
Internet searches for information on suicide return webpages that 10-30% of the time encourage or facilitate suicide attempts. There is some concern that such sites may push those predisposed over the edge. Some people form
suicide pacts online, either with preexisting friends or people than have recently encountered in
chat rooms or
message boards. The Internet, however, may also help prevent suicide by providing a social group for those who are isolated.
[148]
Locations
As of 2010 the Golden Gate Bridge has had more than 1,300 commit suicide by jumping since its construction in 1937.
[152] Many locations where suicide is common have constructed barriers to prevent it.
[153] This includes the
Luminous Veil in Toronto,
[151] and barriers at the
Eiffel Tower in Paris and
Empire State Building in New York.
[153] As of 2011 a barrier is being constructed for the Golden Gate Bridge.
[154] They appear to be generally very effective.
[154]
Notable cases
The
1981 hunger strikes, led by
Bobby Sands, resulted in 10 deaths. The cause of death was recorded by the
coroner as "starvation, self-imposed" rather than suicide; this was modified to simply "starvation" on the death certificates after protest from the dead strikers' families.
[159] Erwin Rommel during World War II was found to have foreknowledge of the
July 20 Plot on Hitler's life and was threatened with
public trial, execution, and reprisals on his family unless he took his own life.
[160]
Other species
Main article:
Animal suicide
As suicide requires a willful attempt to die, some feel it therefore cannot be said to occur in non-human animals.
[112] Suicidal behavior has been observed in
salmonella seeking to overcome competing bacteria by triggering an
immune system response against them.
[161] Suicidal defenses by workers are also noted in a Brazilian ant
Forelius pusillus where a small group of ants leaves the security of the nest after sealing the entrance from the outside each evening.
[162]
Pea aphids, when threatened by a
ladybug, can explode themselves, scattering and protecting their brethren and sometimes even killing the ladybug.
[163] Some species of
termiteshave soldiers that explode, covering their enemies with sticky goo.
[164][165]
There have been anecdotal reports of dogs, horses and dolphins committing suicide, although with little conclusive evidence.
[166] There has been little scientific study of animal suicide.
[167]
