At a time when many high-income nations were beginning to promulgate suicide prevention strategies, a provocative paper demonstrated that focusing on high-risk groups would have much smaller impacts on national suicide rates than policies aiming to influence larger social or ecological forces (such as unemployment). ^{Reference Lewis, Hawton and Jones1} Since then, despite further evidence favouring the population approach, ^{Reference Gunnell and Frankel2–Reference Leitner, Barr and Hobby4} countries such as England, Denmark, Australia and the USA have adopted suicide prevention strategies that seek to combine broad population or universal approaches with complementary high-risk or targeted prevention interventions (Fig. 1). Many such strategies are in place despite a lack of evidence for the effectiveness of key components or for the effectiveness of all interventions acting in concert. The difficulties in evaluating such multilayered initiatives are those of evaluating any complex intervention: identification of the active component(s). Although synergies between interventions are theoretically possible, and highly desirable, these are difficult to demonstrate. ^{Reference van der Feltz–Cornelis, Sarchiapone, Postuvan, Volker, Roskar and Grum5} Such emphasis on the high-risk approach is understandable in the context of pressures to respond to suicidal people encountered in clinical practice. This editorial considers the findings of a study by Gunnell et al (this issue), evaluating interventions to reduce suicide risk in recently discharged psychiatric patients, ^{Reference Gunnell, Metcalfe, While, Hawton, Ho and Appleby6} and the implications of this for suicide prevention strategies.

The contribution of population and high-risk approaches

Population interventions aim to reduce population suicide rates by shifting modal behaviours and improving mental well-being across society as a whole. ^{Reference Knox, Conwell and Caine7} This requires multi-agency, community-oriented work to address social and environmental conditions, employment opportunities, housing and family circumstances within groups held together by common links as well as geographical settings. Such broadly applied prevention efforts include diverse initiatives, for example: to reduce the availability and lethality of suicide methods; to improve detection of depression through educating primary care physicians; to stem the tide of substance misuse and dependence; and to influence media portrayals of suicide and mental illness. Targeted interventions address high-risk groups such as people with severe mental illness, people who self-harm, and specific occupational groups. ^{Reference Lewis, Hawton and Jones1} Although targeted methods focus on relatively small groups (hundreds or thousands), universal methods aim at very large numbers (potentially measured in millions). The prevention paradox is that although suicide rates are lower in the latter group, universal approaches hold the potential to prevent a greater number of deaths. Furthermore, the majority of people who die by suicide – those from the general population – are only recognised posthumously as having been high-risk.

Successive reviews of evidence for the effectiveness of specific suicide preventive interventions have shown an even split between evaluations of high-risk and population approaches, but a clear dominance of population strategies over targeted interventions with respect to positive findings. ^{Reference Gunnell and Frankel2–Reference Leitner, Barr and Hobby4,Reference Knox, Pflanz, Talcott, Campise, Lavigne and Bajorska8} A naturalistic study of a multilayered suicide prevention initiative in the US Air Force found reduced rates of suicide and other violence-related deaths after implementation. ^{Reference Knox, Pflanz, Talcott, Campise, Lavigne and Bajorska8} This hybrid approach offered the potential to reduce suicide risk in a bounded, managed organisation, with the emphasis on universal approaches irrespective of risk. However, it remains uncertain whether such a programme, implemented within a strongly hierarchical organisation, can be applied to less defined communities. More recently, the high-risk approach has been bolstered by studies demonstrating its effectiveness in specific patient groups – those with clear clinical risk factors but representing relatively small numbers. ^{Reference While, Bickley, Roscoe, Windfuhr, Rahman and Shaw9,Reference Fleischmann, Bertolote, Wasserman, Bolhari, Botega and Phillips10} Less encouraging findings have arisen when interventions targeting more loosely defined populations are evaluated. In Australia, the 1995–1997 National Youth Suicide Prevention Strategy (NYSPS) took a multilayered approach, funding interventions targeting young men (a high-risk group nationally) alongside broader health promotion initiatives. When evaluated, local NYSPS activity was found to have no impact on suicide rates in males (or females) aged 20–34 after controlling for the role of period effects (such as concurrent initiatives to address youth unemployment, and changes in labour force characteristics). ^{Reference Page, Taylor, Gunnell, Carter, Morrell and Martin11}

Gunnell and colleagues’ study ^{Reference Gunnell, Metcalfe, While, Hawton, Ho and Appleby6} contributes to the evidence base by finding little impact of interventions to reduce the increased suicide risk in people recently discharged from psychiatric hospitals in England. These targeted interventions were introduced following the 2002 Suicide Prevention Strategy for England: pre-discharge joint case review; risk management plans covering the first 3 months; community follow-up within 7 days of discharge; and more rapid (<48 h) follow-up for patients thought to be at highest risk. The time series analysis of national data compared the periods before and after the introduction of the four interventions. Although finding some evidence for a reduction in admissions for self-harm during the 12 weeks after discharge, they found no evidence for a reduction in the risk of suicide over that period. This study raises important questions about the intended scope of suicide prevention interventions, and the role of the high-risk approach within any national suicide prevention policy.

FIG. 1 The relationship of population and high-risk approaches to levels of suicide prevention.

a. Primordial prevention aims to prevent the emergence of risk factors for suicide. This level of prevention is essentially outside the remit of health services and involves establishing the socioeconomic and cultural conditions that promote mental health and well-being in a population.

b. Primary prevention includes interventions which prevent the onset of suicidal ideation. Examples include support following life events (job loss, bereavement, relationship breakdown), and the early detection of mental disorder together with its evidence-based management.

c. Secondary prevention detects early suicidal ideation or risk factors for suicide (e.g. hopelessness, substance misuse, physical illness) among those with and without mental illness.

d. Tertiary prevention involves risk minimisation for people with a history of self-harm and high levels of suicidal intent. This includes modifying continuing risk factors such as substance misuse and direct access to means.