National differences in intelligence and population rates of suicidal ideation, suicide plans, and attempted suicide

Population rates of suicidal ideation, suicide plans or attempted suicide from three independent multinational epidemiological surveys (the WHO/EURO and WHO SUPRE-MISS studies and a third one) were not significantly associated with national IQ figures. This result conflicts with previous evidence from cross-national studies (by Lester and by Voracek) of a positive ecological correlation between level of national intelligence and rates of completed suicide. Across nations, the indicators for the prevalence of suicidal behavior also lacked close correspondence with suicide rates, which may be due to the higher unreliability of assessing covert suicidal behavior (suicide ideas, thoughts, plans, and, to a lesser extent, also suicide attempts) as compared to suicidal behavior that is indisputably overt (completed suicide). Several alternative explanations for the current nil findings are also discussed.     

Evidence for a positive ecological correlation of regional intelligence and suicide mortality in the United States during the early 20th century

Several contemporary cross-national and intranational geographic studies have reported positive ecological (group-level) associations of intelligence and suicide mortality. These findings are consistent with facts from suicide research and with an evolutionary view of suicidal behavior. The present research extended these accounts cross-temporally. Analysis of E. L. Thorndike's state-level personal quality scores and standardized birth rates of eminent persons, taken as proxy variables for regional intelligence, along with historical state suicide rates (1913-1924 and 1928-1932) showed that intelligence and suicide mortality across the U.S.A. were already clearly positively related during the early 20th century, suggesting time stability of the effect. Within the U.S.A., the effect is possibly due to state differences in the ethnic composition, which correspond to both suicide rates and intelligence proxies. It is argued that the most parsimonious interpretation of these ecological findings remains that they indeed reflect individual-level effects, that a positive link between intelligence and suicide is entirely compatible with positive overall links between intelligence and health and longevity, and that the ultimate explanative background for the positive link between intelligence and suicide may be provided through the framework of Rushton's differential K theory.     

Regional intelligence and suicide rate: new data for Australia and a synthesis of research

Previous research has shown for the most part positive correlations between intelligence and suicide prevalence on the national level. However, this study found proxies for regional intelligence in Australia (international average domain scores from the PISA 2000 study) to be significantly negatively correlated with the total, male, and female suicide rates of the different administrative divisions of Australia, and this finding was independent of regional wealth. A research synthesis of the current results and those from similar studies of other countries (positive correlations for Austria, Belarus, The British Isles, Denmark, and The Netherlands; inconclusive findings for France, Germany, and the USA) was conducted. This synthesis of research findings showed that positive ecological correlations of intelligence with suicide rate were more likely observed for nations with higher suicide rates and poorer general living conditions, whereas there was no relation with national IQ.     

Educational attainment, intelligence, interstate migration, and suicide rates in the United States: rejoinder to Abel and Kruger (2005)

Abel and Kruger (2005) reported a negative association of educational attainment and suicide rate across the United States. Given strong links between intelligence and educational attainment, this appears to be inconsistent with positive associations of intelligence and suicide rate reported in several other geographical studies. However, the apparent inconsistencies may reflect interstate migration within the U.S. adult population. Testing this hypothesis showed that interstate migration was more strongly related to state suicide rates than educational attainment. Thus, the different results obtained by Abel and Kruger could reflect migration effects, which for the U.S. might render adult-age indicators of educational attainment inappropriate to reflect regional variation in intelligence by place of birth.     

Regional intelligence and suicide rate in Denmark

Consistent with evidence from several recent geographical (cross-national and within-nation) studies (by Lester and by Voracek), a positive ecological (aggregate-level) correlation of regional intelligence and suicide rate was found across the seven major geographical regions of Denmark.     

Social ecology of intelligence and suicide in the United States

Two proxy variables for regional intelligence, state-level mean scores of 1994-2004 on the American College Test and of 1982, 1993, 1994, and 1998-2004 on the Scholastic Assessment Test, were consistently positively correlated with the averaged regional U.S. suicide rates of 1990-1994. The effects observed in these ecological (group-level) analyses were of small size, with correlation coefficients ranging from .05 to .25, thus mostly falling below the nominal statistical significance level. The present evidence nevertheless adds to several recent findings from international geographical studies by Lester and by Voracek of a positive association of intelligence and suicide mortality by indicating that this pattern may also exist on the within-nation level.     

National intelligence and suicide rate across Europe: an alternative test using educational attainment data

National mean scores on a historical knowledge test (taken as a proxy for intelligence), stemming from representative samples of male (and female) 9th-grade school students from 26 European countries in a 1999 report by Wilberg and Lynn, were significantly positively associated with the national male (and female) suicide rates, independent of the general quality-of-living conditions in these countries. This finding replicates previous evidence from cross-national studies (by Lester and by Voracek), of a correspondence of higher national IQ to higher suicide rates, with an alternative measure of national IQ that is independent of the national IQ estimates recently published by Lynn and Vanhanen which have been used in prior studies.     

State IQ and suicide rates in the United States

Previous findings pertaining to the direction (positive or negative) of the ecological correlation between intelligence and suicide rates in the USA have been conflicting. Using novel state IQ estimates, derived from the Scholastic Assessment Test, the American College Test, these tests combined, or the National Assessment of Educational Progress state scores, these estimates were not consistently associated to state suicide rates. Whereas ACT-derived state IQ was significantly positively correlated with suicide rates, the correlation with composite ACT-SAT-derived state IQ was significantly negative and with both SAT-derived and NAEP-derived state IQ also negative but not significant. Validity checks pointed to possible methodological problems with the state IQ estimates. Currently available estimates of state IQ, therefore, seem not appropriate to resolve the question of the direction of the ecological correlation of intelligence and suicide mortality across the USA.     

Exponential fitting of suicide rate and national intelligence estimates

Positive ecological (group-level) associations of Lynn and Vanhanen's 2002 national intelligence (IQ) estimates with the suicide rates of men and women across 85 countries and with the suicide rates of the male, female, and total elderly population across 48 Eurasian countries reported recently is extended by the finding that this ecological association was notedly better accounted for by exponential fitting than by linear fitting. This evidence implies that the effect of a shift in the national IQ on the suicide rate is proportional, not absolute. As a rule of thumb, a 5-point shift in national IQ roughly corresponds to a 50% change in the national suicide rate.     

Cross-national social ecology of intelligence and suicide prevalence: integration, refinement, and update of studies

This study integrates, refines, and updates previous findings pertaining to positive ecologic (population-level) associations between intelligence and suicide prevalence across nations by using corrected and revised national IQ estimates and, further, a quality-of-human-conditions index, both recently published by Lynn and Vanhanen. Across a global 85-nation sample of sex-specific total suicide rates and a Eurasian 48-nation sample of sex-specific elderly suicide rates, these were positively associated with updated national IQ estimates. The associations were stronger for the general population than for elderly persons, independent of the quality of human conditions, and notedly stronger in exponential fitting of suicide rates with national IQ than in linear fitting, thereby indicating that shifts or differences in national IQ correspond to proportional, not absolute, changes in suicide rates. Implications of these findings and the question of generalizability of such associations to the individual level are discussed.     

The Relationship Between General Population Suicide Rates and Educational Attainment: A Cross‐National Study

Suicides are associated with both high and low levels of intelligence and educational attainment in both individual‐level and aggregate‐level studies. A cross‐national study examining the relationship between general population suicide rates (y) and educational attainment (x) was undertaken with the a priori hypothesis that the relationship would be curvilinear and follow a U‐shaped curve with the quadratic equation Y = A + BX + CX², where A, B, and C are constants. Data on suicide rates and the Education Index (a proxy measure of educational attainment) were ascertained from the World Health Organization and the United Nations Web sites, respectively. The main finding was the predicted curvilinear relationship between general population suicide rates, in both sexes, and the Education Index fit the above quadratic equation. Given the cross‐sectional study design, a causal relationship cannot be assumed. The impact of educational attainment on general population suicide rates may occur through interaction with other factors, mediation of the effects of other factors, or by its effects being mediated by other factors, and require further study.     

Music and Suicidality: A Quantitative Review and Extension

This article provides the first quantitative review of the literature on music and suicidality. Multivariate logistic regression techniques are applied to 90 findings from 21 studies. Investigations employing ecological data on suicide completions are 19.2 times more apt than other studies to report a link between music and suicide. More recent and studies with large samples are also more apt than their counterparts to report significant results. Further, none of the studies based on experimental research designs found a link between music and suicide ideation, prompting us to do a brief content analysis of 24 suicide songs versus 24 nonsuicide songs from the same album. Using Linguistic Inquiry and Word Count software, we found no difference in the content of the suicide songs and controls, including the percentage of sad words, negative affect, and mentions of death, thus providing an explanation for nonfindings from experimental research. In summary, ecologically based (which capture at‐risk persons not in typical school‐based samples) and more recent investigations (which have used superior or new methodologies) tend to demonstrate a linkage between music and suicidality. Experimental research is needed with a control group of songs from an alternative genre with low suicidogenic content.     

Suicide Terrorists: Are They Suicidal?

Are suicide terrorists suicidal? A review of the worldwide literature on suicide terrorism uncovered five published empirical studies describing data collected from potential suicide terrorists or the surviving friends and families of deceased terrorists. The many discrepancies uncovered between suicide terrorists and other suicides on key factors known to underpin suicidality, suggest that such terrorists are not truly suicidal and should not be viewed as a subgroup of the general suicide population. Nonetheless, methods developed by suicidologists, such as the psychological autopsy, will help increase our understanding of the individual and group factors that underpin suicide terrorism.     

Farewell to the world: suicide notes from Turkey

There has been limited study of suicide in Islamic countries. This paper marks the first study of suicide notes in Turkey, an Islamic country. Using a classification scheme, 49 suicide notes (a rate of 34.5%) were studied. The results show that note writers do not differ greatly from other suicides. Further analysis of younger (<40) and older (>40) suicide note writers reveal few significant differences. Our results, together with the results of classification studies in different countries, suggest that caution is in order in transposing findings from one country to other countries. Future study of suicide notes should, in fact, focus on cross-cultural investigation.     

Intelligence and maturity: meta-analytic evidence for the incremental and discriminant validity of Loevinger's measure of ego development

This review examined whether Loevinger's measure of personality (ego) development is equivalent to the measurement of intelligence. The authors conducted a meta-analysis of 52 correlations between ego level scores and intelligence test scores (retrieved from 42 studies involving 5,648 participants). The weighted average correlation between ego level and intelligence ranged from.20 to.34, depending on the intellectual ability assessed (e.g., verbal intelligence). Adjusting for measurement unreliability increased these values only minimally. The authors also reviewed 16 studies that examined the association between ego level and various criterion variables (e.g., aggressive behavior) after statistically controlling for the effects of intelligence. Ninety-four percent of the tests revealed significant relations between ego level and criterion variables after controlling for intelligence, indicating that ego development and intelligence are not interchangeable constructs. These findings do not support recent speculations concerning the limited value of stage models of maturity, social development, and moral reasoning.     

Firearm possession and violent death: A critical review

This article critically reviews the empirical research on the association of firearm possession with suicide and homicide. Both suicide and homicide reflect intentional behavior with the goal of killing oneself or another person. Firearms provide merely a means of reaching this goal. The possession of a firearm can, therefore, not be a primary cause of either suicide or homicide. However, since a defining characteristic of both suicide and homicide is the success of killing, and since guns are more effective means for reaching this goal than poison or other weapons, the rate of firearm possession can be expected to be positively related to overall rates of suicide and homicide. This prediction has been tested with individual-level as well as macro-level studies. Individual-level studies, which typically use case–control designs, allow a better control than macro-level studies of the cultural, demographic, and economic determinants of suicide and homicide. In macro-level studies, the potential impact of gun possession on overall rates is likely to be confounded by the factors that motivate people to commit suicide or homicide. Despite these methodological limitations, the research reviewed in this article supports the assumption that easy access to firearms increases the risk of dying from violent causes. With very few exception, studies found gun ownership positively related to gun-related suicides and homicides. Furthermore, there is evidence that guns do not merely serve as substitutes for other means of killing, but increase the overall rates of suicide and homicide.     

Serum cholesterol levels and suicide: a meta-analysis

A meta-analysis was performed on studies exploring the link between low levels of serum cholesterol and increased risk of suicide. Follow-up studies found that those with lower cholesterol levels do have a tiny but statistically significant increased risk of completing suicide. Individuals who have attempted suicide in the past have lower cholesterol levels, especially if they used violent methods for suicide. Cholesterol lowering studies, however, did not lead to a significant increase in completed suicide.     

Childhood physical and sexual abuse in depressed patients with single and multiple suicide attempts

Research has shown both childhood physical and sexual abuse to be associated with later suicide attempts, although some studies have not supported these findings. However, few studies have investigated differences in physical and sexual abuse histories among single and multiple suicide attempters. The goals of the current study were two-fold: (a) to replicate previous findings of associations between childhood sexual and physical abuse and suicide attempts, and (b) to explore differences in reports of childhood physical and sexual abuse among single and multiple suicide attempters. While our results supported the findings that individuals with a history of suicide attempts are more likely to report histories of childhood physical and sexual abuse, we did not find a difference in reported abuse between single and multiple suicide attempters. Implications of these findings, as well as implications for future research, are discussed.     

The Hopelessness Scale for Children: Psychometric properties with normal and emotionally disturbed adolescents

The psychometric properties of the Hopelessness Scale for Children (HSC) were evaluated with a sample of 834 normal adolescents and 93 adolescent suicide attempters. Factor analyses studies revealed two factors with both groups. Internal consistency with item-total score correlations were acceptable, while moderate test-retest reliability was found over a 10-week period with the normal sample. Support for the validity of the HSC was provided via studies with the suicide attempter group in which positive correlations with depression and depressive attributional style were found. Predicted differences between the suicide attempters, an outpatient psychiatric sample, and normal controls were also found. However, some items did not appear to discriminate suicide attempters from controls. Results are discussed in terms of the utility of the HSC with adolescents and adolescent suicide attempters and with regard to differences between child and adult samples in hopelessness.     

Variation in suicide occurrence by time of day, day of the week, month, and lunar phase

Previous studies suggest that suicide occurrence varies by month and day of the week, but not by lunar phase. Variation by time of day has never before been adequately examined; to our knowledge, all previous studies have failed to obtain time-of-death information for a large percentage of cases. We examined suicide occurrence among residents of Sacramento County, CA, during the period from 1925 to 1983. Data were abstracted from coroner's autopsy and investigative reports. In contrast to previous studies, data on time of death were available for a large percentage of cases. 4,190 suicide deaths were identified during the study period. Suicide occurrence varied substantially by time of day; for both sexes and for ages under 65 years, the fewest suicide deaths occurred during the early morning hours, from 0401 to 0800. For recent years of the study, suicides occurred most frequently on Monday for both males and females and for most age groups. Variation by month followed no consistent pattern by gender, age, years of the study, or combinations of these factors. Contrary to popular belief, suicide occurrence did not vary by lunar phase.