Person:

Millner, Alexander

Suicide is a leading cause of death around the world. Yet research seeking to uncover the causes of suicide has made little advancement. The purpose of this dissertation is to advance the understanding of one understudied but critical component of suicidal behaviors: how individuals move down the pathway from first thinking about suicide to ultimately attempting to take their own lives. A secondary goal of this work is to examine some flawed methods used in prior research in this area. This ancillary goal results in potential solutions provided in each paper that will allow researchers to collect more reliable data and to draw more valid inferences from these data to better understand the pathway to suicide. In Paper 1, I examine the validity of single-item measurement, a commonly used approach in this area of research in which key suicidal behaviors are assessed with one brief question. The primary finding in that paper is that single-item measurement is associated with significant misclassification of suicidal behavior. In addition, in that paper, I offer and examine an approach that improves validity for self-reported suicidal behaviors. In Paper 2, I attempt to improve on prior research examining suicide planning prior to a suicide attempt and present descriptive data showing how people transition from thinking about suicide to actually attempting (i.e. planning steps they take during this transition). This study revealed that the vast majority of steps occur within 2 weeks and most within 12 hours of an attempt. However, the results also revealed heterogeneous individual differences in the order and timing of planning steps as people moved from thinking about suicide to attempting suicide. In Paper 3, I examine the association between impulsiveness and suicidal behavior, using more comprehensive measures of both constructs than prior studies. Unlike most prior studies, this study also recruits groups that are able to test whether increased impulsiveness could help explain why, among people that think about suicide, some people attempt to kill themselves and others do not. In a secondary goal, I examine whether questions regarding past suicidal behaviors influence self-report measurement potentially causing invalid assessment. The findings from that paper reveal only one dimension of impulsiveness – negative urgency – that differs between suicidal and control participants and none that differ between ideators and attempters. Thus, dimensions of impulsiveness in Paper 3 do not appear to influence attempts among ideators. I also find that answering questions about suicide before self-report measures of impulsiveness influences the degree of impulsiveness reported by suicide attempters and suicide ideators. Specifically, attempters report increased levels impulsiveness compared with ideators when suicide questionnaires are asked first but there is no difference between the groups when participants’ answer impulsiveness questionnaires prior to questions about suicide. In all three papers, I criticize prior research but provide approaches that could lead to modest improvements in methodology and, hopefully, lead to new discoveries in understanding how and why people transition from thinking about killing themselves to attempting suicide.

Suicide is a leading cause of death worldwide. Although research has made strides in better defining suicidal behaviors, there has been less focus on accurate measurement. Currently, the widespread use of self-report, single-item questions to assess suicide ideation, plans and attempts may contribute to measurement problems and misclassification. We examined the validity of single-item measurement and the potential for statistical errors. Over 1,500 participants completed an online survey containing single-item questions regarding a history of suicidal behaviors, followed by questions with more precise language, multiple response options and narrative responses to examine the validity of single-item questions. We also conducted simulations to test whether common statistical tests are robust against the degree of misclassification produced by the use of single-items. We found that 11.3% of participants that endorsed a single-item suicide attempt measure engaged in behavior that would not meet the standard definition of a suicide attempt. Similarly, 8.8% of those who endorsed a single-item measure of suicide ideation endorsed thoughts that would not meet standard definitions of suicide ideation. Statistical simulations revealed that this level of misclassification substantially decreases statistical power and increases the likelihood of false conclusions from statistical tests. Providing a wider range of response options for each item reduced the misclassification rate by approximately half. Overall, the use of single-item, self-report questions to assess the presence of suicidal behaviors leads to misclassification, increasing the likelihood of statistical decision errors. Improving the measurement of suicidal behaviors is critical to increase understanding and prevention of suicide.

Adolescent decision-making has been described as impulsive and suboptimal in the presence of incentives. In this study we examined the neural substrates of adolescent decision-making using a perceptual discrimination task for which small and large rewards were associated with correctly detecting the direction of motion of a cloud of moving dots. Adults showed a reward bias of faster reaction times on trials for which the direction of motion was associated with a large reward. Adolescents, in contrast, were slower to make decisions on trials associated with large rewards. This behavioral pattern in adolescents was paralleled by greater recruitment of fronto-parietal regions important in representing the accumulation of evidence sufficient for selecting one choice over its alternative and the certainty of that choice. The findings suggest that when large incentives are dependent on performance, adolescents may require more evidence to accumulate prior to responding, to be certain to maximize their gains. Adults, in contrast, appear to be quicker in evaluating the evidence for a decision when primed by rewards. Overall these findings suggest that rather than reacting hastily, adolescents can be incentivized to take more time to make decisions when large rewards are at stake.

Suicide is a leading cause of death worldwide. Although research has made strides in better defining suicidal behaviors, there has been less focus on accurate measurement. Currently, the widespread use of self-report, single-item questions to assess suicide ideation, plans and attempts may contribute to measurement problems and misclassification. We examined the validity of single-item measurement and the potential for statistical errors. Over 1,500 participants completed an online survey containing single-item questions regarding a history of suicidal behaviors, followed by questions with more precise language, multiple response options and narrative responses to examine the validity of single-item questions. We also conducted simulations to test whether common statistical tests are robust against the degree of misclassification produced by the use of single-items. We found that 11.3% of participants that endorsed a single-item suicide attempt measure engaged in behavior that would not meet the standard definition of a suicide attempt. Similarly, 8.8% of those who endorsed a single-item measure of suicide ideation endorsed thoughts that would not meet standard definitions of suicide ideation. Statistical simulations revealed that this level of misclassification substantially decreases statistical power and increases the likelihood of false conclusions from statistical tests. Providing a wider range of response options for each item reduced the misclassification rate by approximately half. Overall, the use of single-item, self-report questions to assess the presence of suicidal behaviors leads to misclassification, increasing the likelihood of statistical decision errors. Improving the measurement of suicidal behaviors is critical to increase understanding and prevention of suicide.

Self-injurious thoughts and behaviors (SITBs), including nonsuicidal self-injury, suicidal thoughts, suicide attempts, and suicide death exhibit substantial sex differences. Across most countries, men die by suicide more frequently than women; yet, women think about and attempt suicide more frequently than men. Research on sex differences in nonsuicidal self-injury is less developed; however, nonsuicidal self-injury is historically understood as a primarily female phenomenon. This review describes current research on sex differences across SITBs with a focus on factors that moderate these effects, such as age, race, geographic region, and time. Additionally, this review describes factors that may help to explain why sex differences across SITBs exist, including differences in culture, access to lethal suicide methods, rates of mental illness, and utilization of health care. The role of gender, and particularly non-binary gender, is also discussed. Current understanding of these sex differences is described with an eye toward future research on this topic.

Prior research has shown that most known risk factors for suicide attempts in the general population actually predict suicide ideation rather than attempts among ideators. Yet clinical interest in predicting suicide attempts often involves the evaluation of risk among patients with ideation. We examined a number of characteristics of suicidal thoughts hypothesized to predict incident attempts in a retrospective analysis of lifetime ideators (n=3,916) drawn from a large (n=29,982), representative sample of U.S. Army soldiers. The most powerful predictors of first nonfatal lifetime suicide attempt in a multivariate model controlling for previously known predictors (e.g., demographics, mental disorders) were: recent onset of ideation, presence and recent onset of a suicide plan, low controllability of suicidal thoughts, extreme risk-taking or “tempting fate,” and failure to answer questions about the characteristics of one’s suicidal thoughts. A predictive model using these risk factors had strong accuracy (AUC=.93), with 66.2% of all incident suicide attempts occurring among the 5% of soldiers with highest composite predicted risk. This high concentration of risk in this retrospective study suggests that a useful clinical decision support model could be constructed from prospective data to identify those with highest risk of subsequent suicide attempt.