Studying suicide from the life course perspective: implications for prevention

Suicide is an important contributor to premature mortality accountingfor over 800 000 deaths worldwide every year. Environmentaland genetic factors acting from before birth to old age affectan individual’s risk of suicide. Risk is influenced notonly by psychiatric illness and impulsive behaviour but alsoby factors such as the cultural acceptability of suicide, theease of availability of lethal suicide methods, help-seekingbehaviours in times of crisis and access to effective treatmentsfollowing self-harm. Suicide prevention programmes might usefullyfocus on two discrete areas: the prevention of the psychiatricillnesses that precede suicide and tackling those risk factorsparticular to suicide such as media influences, help-seeking,the availability of methods and the medical management of self-harm.

INTRODUCTION

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INTRODUCTION

Suicide is an important contributor to global patterns of mortality, accounting for over 800 000 deaths a year (World Health Organization, 2002).Since the publication of the government’s suicide prevention strategy (Department of Health, 2002), it has becomea key focus for psychiatric services in the UK.

Unlike many causes of death, suicide is not the result of asingle disease process. It occurs as a consequence not onlyof a range of psychiatric disorders – most commonly depression,substance misuse and schizophrenia – but also of impulsivebehaviour in moments of crisis and in the context of seriousphysical illness (Fig. 1). In this editorial we consider whetherthe study of suicide contributes important aetiological andpreventive insights over and above those gained by studyingits ‘constituent’ disorders (i.e. depression, schizophrenia,etc). We then summarise research evidence for the influenceon suicide risk of factors acting at different stages of thelife course; this evidence is part of a growing body of literaturesuggesting that prenatal and childhood exposures, as well asadult risk factors, may modify an individual’s healthin adulthood (Kuh & Ben Shlomo, 1997). These influencesare integrated into a model of suicidal behaviour that may facilitatea more focused approach for suicide prevention strategies.

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Fig. 1 Life course influences on suicide.

WHY STUDY SUICIDE RATHER THAN ITS ‘COMPONENT’ DISORDERS?

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WHY STUDY SUICIDE RATHER...

Although suicide is unusual in the absence of mental distress,most people with psychiatric disorder and/or suicidal thoughtsdo not kill themselves. Other triggers or vulnerability factorscontribute to risk. For example, in the Christchurch cohort,a discrete set of risk factors – including sexual abuse,a family history of self-harm and low educational achievement – appeared to influence vulnerability to suicidal behaviouramong individuals with depression (Fergusson et al, 2003).

Several other observations indicate that suicide results fromfactors over and above those causing psychiatric disorder.First, the incidence of depression – the most commonantecedent of suicide – is higher in women than in men,whereas in most countries suicide occurs 3–4 times morefrequently in men. Several factors may account for these differences, including stronger social bonds (particularly motherhood) inwomen, gender differences in help-seeking behaviour and genderdifferences in preferred methods of suicide – women tendto favour less lethal methods such as self-poisoning. Second,there are some discrete neurobiological features of suicidalbehaviour (such as deficiency of serotonergic function) thatappear to be associated with suicide, regardless of the underlyingpsychiatric disorder (Mann, 1998). Third, there are ten-folddifferences in national suicide rates within Europe that areunlikely to be due to differences in the prevalence of mentaldisorder. Variations in the cultural acceptability of suicide,socioeconomic conditions, legal definitions of suicide and,possibly, genetic differences are likely to contribute to internationalvariations. Fourth, an important influence on an individualsuccessfully acting on a suicidal impulse is the availabilityof lethal methods of suicide (Clarke & Lester, 1989);this observation is borne out by the fluctuating levels ofsuicide in Samoa in the 1970s and 1980s, which closely mirrored changes in imports of paraquat, a highly toxic pesticide commonlyused as a method of suicide in developing nations (Bowles, 1995).Finally, case fatality following a suicide attempt isinfluenced not only by choice of method but also by accessto effective treatments. For example, reductions in mortalityfrom paracetamol overdose followed the introduction of N-acetylcysteinein the UK (Flanagan & Rooney, 2002), and in Sri Lankamonthly fluctuations in case fatality rates for self-poisoningmirrored the availability of appropriate antidotes (Eddleston et al, 2003).It is noteworthy that most suicide preventionstrategies pay little attention to the medical management ofself-harm. This neglect is understandable for methods of suicidethat result in death soon after the attempt is made, such ashanging and use of firearms, but is less so for other methodsof suicide, particularly self-poisoning, where appropriate medical treatment may be life-saving.

Suicide prevention therefore depends not only on an understandingof how to prevent psychiatric disorder, but also on knowledgeconcerning how other social, economic and medical factors affectsuicide risk.

PRE-ADULT AND GENETIC INFLUENCES ON SUICIDE RISK

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PRE-ADULT AND GENETIC INFLUENCES...

A few studies have examined associations of suicide with indirectmarkers of preadult adversity – birth weight and height.Influences on body growth may also affect neurodevelopmentand the risk of developing mental illness. Birth weight isa marker of foetal growth and may be influenced by maternalnutrition, body size, smoking, health and socio-economic position. Height, as well as being influenced by genes, is influencedby diet, health and psychosocial adversity throughout the growingyears (Mascie-Taylor, 1991). An emerging literature suggeststhat there are associations of suicide with low birth weight(Mittendorfer-Rutz et al, 2004), poor infant growth (Barker et al, 1995)and short stature (Magnusson et al, 2005). Explanationsfor these associations are unclear. They may not be independentof the associations of these measures with depression, schizophreniaand other psychiatric disorders (Thompson et al, 2001; Cannon et al, 2002).Programming of the hypothalamic – pituitaryaxis has been suggested as a possible explanation for observedassociations of suicide with measures of growth in early life (Barker et al, 1995).

As already described, vulnerability to self-harm may be increasedby factors such as a history of childhood sexual abuse anda family history of self-harm (Fergusson et al, 2003). Theassociation with a family history of self-harm highlights theimportance either of genetic susceptibility or of behaviours learnt from other family members – or a combination ofthe two phenomena. Twin and adoption studies indicate thatthere is a genetic component to suicide. Although a numberof brain pathways have been investigated, the strongest evidenceis for a role of the serotonergic system (Mann, 1998). Thispathway is also implicated in aggressive and impulsive behaviours,both of which may contribute to suicidal behaviour. It is likely,although not proved, that the effects of environmental stressorson suicide risk may differ in those with and those withoutgenetic predisposition to suicidal behaviour.

Psychological mechanisms underlying associations of childhoodadversity with suicidal behaviour are not fully understood.A possible pathway is through the effects of childhood traumaon the memory system. The hypothesis has been put forward thattraumatic events in childhood result in impaired autobiographicalmemory, which impairs problem-solving and may result in suicidalbehaviour in times of crisis (Williams & Pollock 2000).

ADULT INFLUENCES ON SUICIDE

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ADULT INFLUENCES ON SUICIDE

The main psychiatric disorders contributing to suicide riskin adults are depression and schizophrenia. A number of socialand economic factors – unemployment, divorce, seriousmedical illness and substance misuse – are also commonlyassociated with suicide. In contrast, parenthood and being ina stable relationship appear to be protective (Qin et al, 2003).

One problem that besets observational research into the relativeimportance of mental illness and socio-economic risk factorsfor suicide is our limited understanding of the nature of theunderlying causal pathways for these associations. For example,Danish studies suggest that there is only a weak associationbetween unemployment and suicide after controlling for an individual’spast psychiatric history among other exposures (Mortensen etal, 2000). This may be interpreted as suggesting that peoplewith psychiatric illness are more likely to lose their jobor find it difficult to gain employment, and that this explainsthe association of unemployment with suicide. However, analysisof temporal trends in unemployment and suicide shows that risesin unemployment are associated with increases in suicide (Gunnell et al, 1999).It seems improbable that the rises in unemploymentare caused by rises in mental illness. More plausibly, increasesin unemployment result in greater levels of depression anddistress and this in turn influences trends in suicide. Bothpathways are likely to contribute to associations of suicide with unemployment. Similarly, being unmarried is associatedwith an increased risk of suicide (Qin et al, 2003) –but does the absence of a close relationship cause psychiatricillness, or vice versa? Multivariable analyses of large data-setssuggest that both pathways may contribute (Qin et al, 2003).

Serious physical illness in adulthood is also associated withincreased suicide risk. Evidence is strongest for cancer andneurological disorders such as multiple sclerosis. It is noteworthythat the increased risk of suicide associated with AIDS appearsto have declined with the advent of new therapies (Stenager & Stenager, 2000).

Religious beliefs and other cultural factors may influence thelikelihood of an individual acting upon suicidal thoughts (Neeleman & Lewis, 1999).The reporting and portrayal of fictionalor actual suicides in the media has also been found to influencepatterns of suicidal behaviour (Hawton & Williams, 2002). The media and religious beliefs may influence both the acceptabilityof suicide and an individual’s choice of method of suicide.More crudely, changing availability of particularly lethalmethods of suicide may influence rates. In Britain, the decreasedlethality of domestic gas, the most commonly used method ofsuicide in the 1960s, is thought to have contributed to the decline in the national suicide rate at this time (Kreitman, 1976).

CONCLUSIONS

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CONCLUSIONS

Genetic and environmental factors acting at different stagesof the life course are associated with the risk of suicide.Such risk factors are more extensive than those of relevanceto the aetiology of psychiatric disorder. An individual’srisk is also influenced by the chosen suicide method and theavailability of medical services to manage the consequencesof the suicide attempt. Figure 1 illustrates the possiblepathways through which factors acting from before birth to immediatelyproximal to the suicide attempt might influence an individual’sdecision to attempt suicide and the outcome of such a decision.A fuller understanding of factors operating across the lifecourse that either protect against or precipitate suicide,as well as the key periods of development when they act, willprovide useful insights into its prevention.

The evidence reviewed here suggests that national suicide prevention programmes might usefully define two discrete areas of work.The first should focus on the prevention of psychiatric disorder.The second should focus on risk factors particular to suicide,such as media influences and the availability of methods ofsuicide and medical treatment. Striking a balance between thesetwo approaches is important and there might be times when the two would conflict. For example, although prevention of suicideis a priority for all mental health services, there is a possibilitythat some methods used to reduce risk in those with psychiatricdisorder, such as increased in-patient observation and removalof belts and shoelaces, could reduce the therapeutic valueof in-patient treatment. In the wider community, prevention of suicide by reducing access to means alone does not addressthe root cause of distress that results in some people takingtheir own lives, and does not necessarily signal an improvementin the mental health of the wider population.

REFERENCES

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