Suicide remains a leading cause of death worldwide1. A key reason for limited progress is inadequate understanding about the transition from suicidal ideation to suicide attempts. This knowledge is important because the majority of instances of suicidal ideation do not lead to suicide attempts. A World Health Organization study found that approximately two-thirds of individuals with suicidal ideation never make a suicide attempt2, and a population-based study found that only 7% of individuals with suicidal ideation attempted suicide during the subsequent two years3.

Unfortunately, little is known about when or for whom ideation leads to attempts. For example, psychiatric disorders that predict suicidal ideation only weakly or negligibly predict progression from ideation to attempts2. Similarly, in meta-analytic data, variables such as depression and hopelessness are strong correlates of suicidal ideation, but are weakly or negligibly associated with attempts among ideators4. Currently, not even a single strong predictor of suicide attempts among ideators has been identified.

To advance suicide knowledge and prevention we must better understand the transition from suicidal ideation to suicide attempts. A response to this need may be provided by the ideation-to-action framework, which suggests that the development of suicidal ideation and the transition from suicide ideation to attempts are distinct processes with distinct predictors and explanations5. This framework has implications for suicide research, risk assessment, intervention, and theory.

Regarding research, the framework underscores the need for studies to identify variables that help predict and explain transition from ideation to attempts. Many studies on suicide attempts examine differences between attempters and non-attempters; however, because all (or virtually all) attempters have suicidal ideation, this common research design confounds attempts and ideation, making it impossible to tell what the differences are attributable to. Studies seeking to identify predictors of suicide attempts must in some way control for suicidal ideation; one option is to conduct analyses that test what predicts suicide attempts among those with ideation.

The framework also has implications for risk assessment and prevention. One implication is that suicide risk factors should not comprise a single list, but be organized according to whether they raise risk for suicidal ideation, suicide attempts among ideators, or both. For example, research to date suggests that depression primarily is a risk factor for suicidal ideation, access to lethal means is a risk factor for suicide attempts among those with ideation, and nonsuicidal self-injury increases risk for both. The framework has similar implications for intervention. Specifically, any intervention for suicide risk should be clear about which aspects are meant to reduce suicidal ideation and which are meant to stop transition from ideation to attempts.

The ideation-to-action framework also applies to suicide theory. Historically, different theories of suicide emphasized different factors, such as social isolation, psychological pain, and hopelessness; these theories have been extremely beneficial for guiding research and providing a foundation that informs contemporary theories. At the same time, traditional theories share a common limitation: they tend to treat suicidality as a single phenomenon in need of a single explanation1, 6. As a result, these theories did not provide separate explanations for suicidal ideation and suicide attempts.

In this context, the Interpersonal Theory of Suicide (IPTS)7 rep­resents an important theoretical advance. The IPTS provides separate explanations for the development of suicidal ideation and the progression from suicidal ideation to suicide attempts. Specifically, the IPTS suggests that suicidal desire is caused by thwarted belongingness and perceived burdensomeness, whereas progression from suicidal desire to suicide attempts occurs when one has acquired the capability to make a suicide attempt. Thus, the IPTS may be viewed as the first of a new generation of suicide theories that positioned themselves within an ideation-to-action framework6.

The most recent ideation-to-action theory is the Three-Step Theory of Suicide (3ST)8. In brief, the 3ST suggests that: a) suicidal ideation is caused by the combination of unbearable pain (usually psychological) and hopelessness, b) suicidal ideation is strong when one’s pain exceeds or overwhelms one's connectedness (to valued people, communities, or sources of purpose and meaning), and c) transition from strong suicidal ideation to potentially lethal suicide attempts is facilitated by dispositional, acquired and practical contributors to capability for suicide. Thus, the 3ST is a concise theory that explains suicide in terms of just four variables: pain, hopelessness, connectedness, and suicide capability.

A growing body of research – including studies on correlates of suicidal ideation and suicide attempts, predictors of suicidal ideation and suicide attempts, motivations for suicide, warning signs for suicide and suicide attempts, and means safety interventions – support the validity of the 3ST8. As a result, the 3ST has been incorporated into suicide education and prevention programs, including continuing education courses, campus-based suicide prevention programs, and self-help suicide prevention materials8.

An advantage of the 3ST is that it provides a context for understanding the impacts of diverse biopsychosocial risk factors and interventions. Specifically, anything that impacts pain, hopelessness, connection, and/or suicide capability would be expected to impact suicide risk. For example, if an antidepressant were to reduce suicide risk, we might hypothesize that this occurs by reducing depression, and thus psychological pain. We might further hypothesize that an improvement in depression may increase one’s sense of hope for the future, and/or enhance one's ability to engage with valued connections. Similarly, the 3ST can be applied to understand elevated risk in various populations. For example, increased suicide risk in transgender individuals is likely due to increased pain, hopelessness, and disconnection caused by widespread prejudice and discrimination, whereas elevated suicide risk in certain medical professionals may be best explained by elevated suicide capability (i.e., knowledge and access to lethal means). Thus, the 3ST can improve understanding of suicide risk across a variety of clinical, social and scientific contexts.

Despite recent theoretical advances, it remains critical for the field to continue to clarify the conditions under which ideation results in attempts. Perhaps the most promising variable to date explaining this progression is suicide capability. As noted above, this construct was first introduced in the IPTS7 and subsequently elaborated by the 3ST8. In short, because suicide involves the potential for pain, injury and death, and because people are biologically (and arguably evolutionarily) disposed to fear and avoid pain, injury and death, making a suicide attempt requires the capability to overcome these barriers.

Different definitions and measures of suicide capability have been proposed, and much of the evidence is mixed. Perhaps the most robust finding is that risk of attempts among ideators is higher when practical capability is higher (practical capability refers to knowledge of, access to, and expertise with lethal means). This conclusion is supported not only by recent studies demonstrating a relationship of practical capability to suicide attempts8, but also by a long history of research showing impacts of access­ to lethal means and means safety interventions on suicide rates9.

Moving forward, it is imperative that research better illuminate when and for whom suicidal ideation leads to suicide attempts. This effort requires use of multiple measurements within longitudinal designs so that the ebb and flow of variables that contribute to suicidal ideation and attempts can be captured precisely and accurately. Understanding the phenomena of suicidal ideation and suicide attempts through the ideation-to-action lens will accelerate the development and refinement of essential suicide research, theory and clinical care.