This study documented three noteworthy results. First, we provided estimates of the 12-month prevalence of suicidal behaviors among adults (18+ years-old) in 21 countries. A recent review of studies on the 12-month prevalence of suicidal behaviors reported widely-varying estimates found in prior studies.2
The estimates obtained in the current study were in the lower end of these ranges for each suicidal behavior. This was most likely the result of two features of our study: we used conservative items for the assessment of each suicidal behavior (e.g., presence of suicide ideation required that a person have “seriously” thought about committing suicide rather than having merely “thoughts of death” as in some prior studies), and we used large representative samples of respondents from the general population (i.e., rather than small selective samples that may be at higher risk for suicidal behaviors, such as young adults or those in a clinical setting). Although it has been suggested that suicidal behaviors may differ between developed and developing countries,51, 52
consistent with our prior report on the cross-national lifetime prevalence of suicidal behaviors1
we found no differences in 12-month prevalence between developed and developing countries. The prevalence estimates for suicide attempts documented in this study complement cross-national data on suicide mortality maintained by the WHO53
and suggest that across the countries examined here there are approximately 14.6 suicide attempts for every one suicide death (Median ratio: 14.6; IQR: 9.1–53.7)—a ratio consistent with those documented in prior reports.54, 55
Second, we identified risk factors for 12-month suicidal behaviors across both developed and developing countries. Replicating the results of prior studies, female sex, younger age, lower education and income, unmarried status, unemployment, parent psychopathology, childhood adversities, the presence of every mental disorder assessed, and psychiatric comorbidity all emerged as significant risk factors for suicidal behaviors in this study.7, 56–58
Interestingly, analyses revealed that most of these factors are associated with suicide attempts because they are predictive of suicide ideation even though they do not significantly predict the occurrence of suicide attempts among those with suicide ideation. For instance, although the presence of a DSM-IV mental disorder was associated with significantly higher odds of experiencing suicide ideation in virtually every instance, few mental disorders predicted suicide attempts among those with ideation. Among those few disorders, conduct disorder emerged as the strongest and most consistent predictor of suicide attempts, with anxiety and substance use disorders also showing significant results in several instances. These findings are consistent with those from a recent study of the prediction of lifetime suicide attempts1
and suggest that disorders characterized by impulse-control and anxiety may be most important in predicting the transition from suicidal thoughts to suicide attempts.
Our analyses also add to the growing literature on the importance of prior history of suicidal behaviors in predicting subsequent suicide attempts.27, 28, 59
The current study extends earlier work on this topic by differentiating two processes involved in the transition from suicidal thoughts to attempts. In line with prior findings, a history of prior suicide attempt was found to be strongly predictive of 12-month suicide attempts.28, 34, 60
Our analysis adds to prior research by showing specificity in this process, though, such that a history of unplanned (impulsive) suicide attempts predicts subsequent unplanned attempts (but not planned ones), while a history of planned attempts predicts subsequent planned attempts (but not unplanned ones). This is an important specification for clinicians working with potentially suicidal patients, especially patients with a history of unplanned suicide attempts.
We also found that risk of the transition from suicidal thoughts to attempts was significantly lower
among those who had thought of suicide in the past but never made an attempt than even among those who had never had suicidal thoughts before the past 12 months. This intriguing result, coupled with the earlier finding that more than 60% of the transitions from suicide ideation to attempt occur in the first year after onset of ideation,1
suggests that resisting the urge to make a suicide attempt when suicidal thoughts first occur is associated with decreased risk of acting on these thoughts when they return. An important next step is to study people with a history of ideation who never made a suicide attempt in greater detail in an effort to understand what characterizes such people (e.g., good impulse control, low severity of suicide ideation) and what strategies they use to resist the urge to make a suicide attempt. Importantly, these findings should not be interpreted to mean that those who have thought about suicide in the past but not made an attempt are not at risk of making a future suicide attempt, but only that evidence of not having made a previous attempt despite having suicide ideation is a predictor of low risk of future attempts compared to people with more recent first onset of ideation. It is important for clinicians to conduct a thorough risk assessment with each patient encountered and to use ongoing monitoring of suicide risk.61–63
Third and perhaps most important, we developed risk factor indices for 12-month suicide attempts tailored for planned versus unplanned attempts and with versions available for both developed and developing countries. Although only a handful of factors emerged as predictors of suicide attempts among ideators, our analyses revealed that all four summary risk indices using these factors showed good discrimination properties (as evidenced by moderate to substantial AUCs of .74–.80) in the total sample that also performed quite well when applied to most developed countries and to a substantial minority of developing countries. These results suggest that the indices might prove useful in predicting suicide attempts in clinical settings; however, this remains an important question for future study. Although suicide prevention programs that include a focus on screening in order to identify people at elevated risk for suicide are among the only prevention programs that have shown an ability to decrease the rate of suicide death,64
such programs are not used in most clinical settings. What has been lacking is an empirically derived screening instrument that can be feasibly used in clinical settings to assess key risk factors and determine a person’s level of risk for suicide attempt. Although it will be important to test the prospective predictive ability of these indices in actual clinical settings, the risk indices developed in this study represent an important initial step toward bridging the gap between the science and practice of suicide risk assessment.
Several additional features of the risk indices developed here warrant further comment. First, our risk indices had strong correlations with planned and unplanned attempts among suicide ideators from a large and heterogeneous set of developed and developing countries, suggesting these indices may have good generality in the prediction of suicide attempts—and indirectly supporting the cross-cultural validity of the WMH-CIDI measure used to assess these risk factors. Second, the performance of our risk indices was only slightly lower that the one developed using a much more homogenous sample34
and is similar to the AUC reported among a selective group of psychiatric patients.65
Our results also suggest that we may be able to predict suicide attempts with the same level of accuracy possible in other areas of medicine in which actuarial approaches that combine risk factors from multiple domains have proven more accurate than clinical prediction, such as in the prediction of violence and sexual offending30, 66
and the prediction of death from natural causes among the elderly.67
Third, and finally, it is important to note that these indices are not intended to serve as a comprehensive suicide assessment by themselves, but instead may be best used to identify those at high risk for suicide attempt so that they can receive a more focused, in-depth assessment of current risk for suicidal behavior.
The results of this study should be interpreted with four important limitations in mind. First, our analysis was based on retrospective self-reports. This concern is limited somewhat by our focus on suicide attempts in only the past 12-months; however, it is possible that time-varying risk factors (e.g., marital status, income) reported for the past 12-months may have changed after respondents’ suicide attempts. Retrospective recall of childhood adversities and parental psychopathology might have been influenced by respondents’ current mood or recent suicide attempt.68, 69
Given these issues, these results should be considered preliminary until the risk indices developed are cross-validated prospectively. Second, although the overall response rate was at an acceptable level, response rates varied across countries and in some cases were below commonly accepted standards. We controlled for differential response using post-stratification adjustments, but it is possible that response rates were related to the presence of suicidal behaviors or mental disorders, which could have biased cross-national comparisons. Third, there may have been cross-national differences in the willingness to report on suicidal behaviors and in the interpretation of items assessing risk factors. Significant efforts were dedicated to carefully translating and back-translating the WHO-CIDI used in this study in order to minimize such concerns;36
however, differences in factors such as the stigma about suicide and childhood maltreatment are likely to persist cross-nationally despite these efforts. Fourth, although we examined a broad set of potential risk factors, many important factors were not included in this study. Psychotic disorders, although known to be associated with suicidal behavior, were not assessed because prior studies have shown that they are dramatically overestimated using structured interviews such as the WMH-CIDI.70, 71
We also did not include many family history (e.g., history of schizophrenia or bipolar disorder), psychological (e.g., hopelessness), social (e.g., lack of social support) or biological (e.g., serotonergic functioning) factors known to be associated with suicidal behaviors. Any one study cannot assess all such factors; however, the limited focus used is important to bear in mind when interpreting the results.