Despite being a leading cause of death, both in the UK and worldwide, there is little hard evidence to explain why some people attempt suicide.
Most people who choose to end their lives do so for complex reasons. Research has shown that in the UK many people who die by suicide have a mental illness, most commonly depression or an alcohol problem.
In many cases, suicide is also linked to feelings of hopelessness and worthlessness.
Vulnerability to suicide
Many experts believe a number of things determine how vulnerable a person is to suicidal thinking and behaviour. These include:
- life history - for example having a traumatic experience during childhood, a history of sexual or physical abuse or a history of parental neglect
- mental health - for example developing a serious mental health condition, such as schizophrenia (see below)
- lifestyle - for example if you misuse drugs or misuse alcohol
- employment - such as poor job security, low levels of job satisfaction or being unemployed
- relationships - being socially isolated, being a victim of bullying or having few close relationships
- genetics and family history (see below)
In addition to these, a stressful event may push a person 'over the edge', leading to suicidal thinking and behaviour.
It may only take a minor event, such as having an argument with a partner. Or it may take one or more stressful or upsetting events before a person feels suicidal, such as the break-up of a significant relationship, a partner dying or being diagnosed with a terminal illness.
Mental health conditions
It is estimated that 90% of people who attempt or die by suicide have one or more mental health conditions. Conditions that lead to the biggest risk of suicide are described below.
Severe depression causes symptoms of low mood, tiredness, loss of interest, despair and hopelessness that interfere with a person's life. People with severe depression are much more likely to attempt suicide than the general population.
Bipolar disorder causes a person's mood to swing from feeling very high and happy to feeling very low and depressed. About 1 in 3 people with bipolar disorder will attempt suicide at least once. People with bipolar disorder are 20 times more likely to attempt suicide than the general population. Most people with bipolar disorder end their lives shortly after entering a depressive phase.
Schizophrenia is a long-term mental health condition that typically causes hallucinations (seeing or hearing things that are not real), delusions (believing in things that are not true) and changes in behaviour. It is estimated that 1 in 20 people with schizophrenia will take their own life.
People with schizophrenia are most at risk of suicide when their symptoms first begin. This is because they frequently suffer loss at this time - for example, loss of employment and relationships. The risk tends to reduce over time.
People with schizophrenia are also at increased risk of self harm.
Borderline personality disorder
Borderline personality disorder is characterised by unstable emotions, disturbed thinking patterns, impulsive behaviour and intense but unstable relationships with other people. Self-harm is often a key symptom of this condition.
It is estimated that just over half of people with borderline personality disorder will make at least one suicide attempt.
People with a borderline personality disorder often have a history of childhood sexual abuse and have a particularly high risk of suicide.
Anorexia nervosa is an eating disorder. People with anorexia feel fat and try to keep their weight as low as possible. They do this by strictly controlling and limiting what they eat, as well as sometimes inducing vomiting. It is estimated that around 1 in 5 people with anorexia will make at least one suicide attempt.
Other risk factors for suicide
Other things that can make a person more vulnerable to suicidal thoughts, include:
- being gay, lesbian or transgender, arising from the prejudice these groups often face
- being in debt
- being homeless
- being a war veteran
- being in prison or recently released from prison
- working in an occupation that provides access to potential ways of dying by suicide, such as working as a doctor, nurse, pharmacist, farmer or as a member of the armed forces
Antidepressants and suicide risk
Some people experience suicidal thoughts when they first take antidepressants. Young people under 25 seem particularly at risk.
Contact your GP immediately or go to your local hospital if you have thoughts of killing or harming yourself at any time while taking antidepressants.
It may be useful to tell a relative or close friend that you have started taking antidepressants and to ask them to read the leaflet that comes with your medication. Ask them to tell you if they think your symptoms are getting worse or if they are worried about changes in your behaviour.
Genetics and suicide
It has been known for some time that suicide - as well as some mental health problems - can run in families. This has led to speculation that certain genes may be associated with suicide.
Recent research has identified several genetic mutations (when genetic instructions inside the cells become scrambled) that may disrupt the chemical make-up of the brain, making a person more vulnerable to suicidal thinking and behaviour.
However, it would be too simple to claim that there is a "suicide gene" and that whoever had a copy of that gene would attempt suicide. Suicide is not just a matter of biology. It is a complex phenomenon involving a wide range of factors.
A newer theory of suicide
A newer theory about suicide, devised by an American psychologist called Thomas Joiner, states that three main factors can cause someone to turn to suicide. They are:
- a perception (usually mistaken) that they are alone in the world and that no one really cares about them
- a feeling (again usually mistaken) that they are a burden on others and that people would be better off if they were dead
- fearlessness towards pain and death
Fearlessness poses the biggest risk that someone will commit a successful suicide attempt.
The theory argues that fearlessness towards pain and self-harm may be learnt over time, which could explain the strong association between self-harming behaviour and suicide.
People who are regularly exposed to the suffering and pain of others may develop this fearlessness over time. This could help explain why suicide rates are higher in occupations that are linked to such exposure, such as soldiers, nurses and doctors.