LONDON: There are many factors which can increase the risk of suicide - including being male, previous self-harm, psychiatric and/or drug/alcohol disorders, upbringing, exposure to suicide in the media, and smoking. Among employed people, doctors (particularly women), vets, nurses, dentists and farmers are all at increased risk - because they have easy access to drugs or poisons which can be used for suicide. In a Seminar in this week's edition of The Lancet, Professor Keith Hawton, Centre for Suicide Research, University of Oxford, UK, and Professor Kees van Heeringen, Unit for Suicide Research, University Hospital, Gent, Belgium, discuss these trends.
An estimated one million people die from suicide each year, equating to one every 40 seconds - but suspected under-reporting in many countries means this is probably a big under-estimate. Suicide accounts for 1.5% of deaths worldwide and is the tenth leading cause of death. Within Europe, rates are generally higher in northern countries than in southern countries. An effect of latitude on suicide rates was found in Japan, suggesting an influence of the daily amounts of sunshine on suicide. However, countries at about the same latitude, such as the UK and Hungary, can have substantially different rates of suicide. Suicide is a major concern in former Soviet states. More than 30% of suicides worldwide happen in China, where 3.6% of all deaths are by suicide. In developed countries, the male-to-female ratio for suicide is between two and four to one, and this seems to be increasing. Asian countries typically show much lower male-to-female ratios, but these might also be increasing; although in China more women than men die by suicide.
Suicide rates are highest in elderly people in most countries, but in the past 50 years rates have risen in young people, particularly men. Suicide rates peak in Spring, especially among men. People born in spring or early summer, particularly women, are at increased risk of suicide. European Americans have higher suicide rates than Hispanic or African Americans, though this gap is narrowing due to increased suicides in young black people. Indigenous populations, eg, Aboriginies in Australia and Native Americans, have higher suicide rates, possibly due to cultural/societal marginalisation and higher levels of alcohol abuse.
Suicide rates are, not surprisingly, higher in unemployed than employed people - in part, high rates are associated with mental illness, which is also associated with unemployment. Among people in employment, some occupational groups are at increased risk of suicide. Medical practitioners have a high risk in most countries, but female doctors are generally most at risk. Nurses also have a high risk. In both these professional groups, access to poisons seems to be an important factor in determining the high rates. Among doctors, anaesthetists are particularly at risk, with anaesthetic drugs being used in many suicide deaths. Several other high-risk occupational groups (eg, dentists, pharmacists, veterinary surgeons, and farmers) also have easy access to means for suicide.
In general, men tend to choose more violent means for suicide (eg, hanging or shooting) and women less violent methods (eg, self-poisoning). Different populations use differing suicide methods, eg, women in South Asia commonly set fire to themselves to commit suicide. Access to specific methods might be the factor that leads to translation of suicidal thoughts into action. In the USA, firearms are used in most suicides, with risk of their use being highest where guns are kept in households. In rural areas of many developing countries, ingestion of pesticides is the main method of suicide, reflecting toxicity, easy availability, and poor storage. As many as 30% of global suicide deaths may involve ingestion of pesticides.
Mental health problems are a major factor in suicide. Some 90% of people who take their own life are believed to have some kind of psychiatric disorder. Depression increases the risk of suicide by 15 to 20 times, and about 4% of people with depression die by suicide. Clinical predictors of suicide in depressed people include previous self-harm, hopelessness, and suicidal tendencies. Around 10-15% of patients with bi-polar disorder die by suicide, with risk at its highest during the early part of the illness. Some 5% of people with schizophrenia also die by suicide. Alcohol misuse, anorexia nervosa, attention deficit hyperactivity disorder, and body dismorphic disorder all increase suicide risk - wit the last example partly explaining why risk increases in women after breast enlargement surgery.
Physical health also plays its part, but with some strange findings. Surprisingly, while people with higher-body mass index are at increased risk of depression, they have a lower risk of suicide (15% decrease in suicide risk for each 5 kg / m2 increase in body-mass index). The reasons for this are unknown. Cancer, particularly of the head and neck, HIV/AIDS, multiple sclerosis, epilepsy, and a range of other conditions also increase suicide risk.
Other factors that can increase suicide risk include physical and sexual abuse throughout childhood, population-wide events such as natural disasters and deaths of celebrities. Suicide rates rose by 17%* following the death of Diana, Princess of Wales in 1997, with the increase being more pronounced in women in her age group. War decreases suicide risk, perhaps due to the social cohesion it can create in communities. People bereaved by suicide are themselves at increased risk, and clusters of suicides can happen in communities or through internet contact. The authors add: "A substantial body of evidence indicates that certain types of media reporting and portrayal of suicidal behaviour can influence suicide and self-harm in the general population."
Post-mortems of suicide deaths have shown changes to the central neurotransmission functions, for example to the serotonin (mood-improving hormone) system. Low cholesterol concentrations are associated with increased suicide risk, but the risk is higher when low cholesterol has been achieved through diet rather than statins. The authors speculate this could be because people who diet are more at risk of mental health problems, but say there is little evidence to back this. Family history of suicide at least doubles the risk of suicide for girls and women. Suicide occurs in tandem more in identical twins compared with non-identical twins. While evidence is limited, high levels of lifetime aggression are associated with a high risk of suicide, while impulsivity also increases the risk. Suicide rates rise throughout teenage years, especially in boys, and family 'transmission' of suicide risk occurs, especially on the maternal side.
Prevention of suicide is a difficult concept due to high number of factors involved, but strategies can target high risk groups or aim to reduce the risk to the population as a whole. Each person with depression should be screened for suicide risk by specifically asking about suicidal thoughts and plans. The authors say: "In cases of high or imminent suicide risk, immediate action is needed, including vigilance and supervision of patients, perhaps through hospitalisation, removal of potential methods of suicide, and initiation of vigorous treatment of associated psychiatric disorder." They also discuss a recent meta-analysis of randomised trials which suggested that the risk of death and suicide in people with mood disorders was reduced by 60% in those taking lithium.
Removal of means used for suicide is important in management of individuals, and modification of general access to dangerous means can also be effective in suicide prevention at the population level. The authors say: "One striking example of the effect of availability of a common means of suicide was the large reduction in suicides following the change of the UK gas supply from toxic coal gas, the most common method used for suicide during the early 1960s, to non-toxic North Sea gas." Introduction of safety barriers on bridges and increased gun control can also decrease the risk of suicide, as can safer storage of pesticides and poisons, especially in rural areas of developing nations. School programmes to improve mental wellbeing, and more stringent control of media reporting of suicide could also have a preventive effect.
The authors conclude: "Future research must focus on the development and assessment of empirically based suicide-prevention and treatment protocols. The challenges of preventing suicide in developing countries need particular attention, because most research comes from developed countries, but most deaths by suicides happen in developing countries.