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Keywords:

  • prevalence;
  • risk factor;
  • suicide;
  • World Mental Health Survey

Abstract

  1. Top of page
  2. Abstract
  3. METHOD
  4. RESULTS
  5. DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES

Aim:  Suicide is a major public health concern in Japan but little is known about the prevalence of and risk factors for suicidal ideation, plans, and attempts. The aim of the present study was to clarify the prevalence of and risk factors for important suicide-related outcomes.

Methods:  Important suicide-related outcomes and risk factors were assessed in face-to-face interviews with 2436 adult respondents in seven areas as part of the World Health Organization (WHO) World Mental Health Survey Initiative. Mental disorders were assessed with the WHO Composite International Diagnostic Interview (CIDI).

Results:  The lifetime prevalence estimates of suicidal ideation, plans, and attempts were 10.9%, 2.1%, and 1.9%, respectively. Risk of suicide plans and attempts was highest when suicidal ideation occurred at an early age and within the first year of ideation. In middle-aged individuals, the period after first employment and the presence of mental disorders were risk factors.

Conclusions:  Risk of suicide plans and attempts is highest when suicidal ideation occurred at an earlier age and within the first year of ideation. Mental disorders are as predictive of the suicide-related outcomes examined here, and comorbidity is an important predictor.

SUICIDE AND SUICIDE-RELATED outcomes – suicidal ideation, plans, and attempts – are a major public health concern. Despite these situations, basic data on the prevalence of and risk factors for suicide-related outcomes are scarce in Japan. The purpose of the present study was to estimate the prevalence of suicide-related outcomes and to examine potential risk factors for these outcomes using data from a study conducted as part of the World Health Organization (WHO) World Mental Health (WMH) Survey Initiative (WHO World Mental Health Consortium, 2004). Several studies have provided valuable information about suicidal behaviors across several countries. This study was designed to overcome many of the limitations of prior work1–3 in this area, especially by introducing data on age and time of suicide-related outcomes, and represents the largest and most representative examination of suicide-related outcomes ever conducted in Japan.

METHOD

  1. Top of page
  2. Abstract
  3. METHOD
  4. RESULTS
  5. DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES

Respondent samples

The WMH surveys were carried out in three cities (Okayama and Tamano in Okayama prefecture and Nagasaki) and four rural municipalities (Kushikino, Fukiage, Ichiki, and Higashiichiki in Kagoshima prefecture) in Japan in 2002 and 2004. These sites were selected in consideration of both geographic variation and the availability of site investigators. From a voter registration list or a resident registry, a random sample was selected from residents aged 20 years and older at each survey site. We excluded subjects who had died, moved or had been institutionalized. The surveys were conducted using face-to-face interview by trained lay interviewers among multi-stage household probability samples. The total sample size was 2436, and the response rates were 65.7% (Okayama), 56.4% (Tamano), 26.4% (Nagasaki), 65.7% (Kushikino), 81.6% (Fukiage), 71.2% (Ichiki), and 69.8% (Higashiichiki), with an average of 58.4%.

Procedures

All respondents completed a Part I interview that contained core diagnostic assessments, including the assessment of suicide-related outcomes. All Part I respondents who met criteria for any disorder and a subsample of approximately 25% of the remaining respondents were given a Part II interview that assessed potential correlates and disorders of secondary interest. Data were weighted to adjust for this differential sampling of Part II respondents, differential probabilities of selection within households, and to match the samples to population sociodemographic distributions.

Standardized interviewer training procedures, WHO translation protocols for all study materials, and quality control procedures for interviewer and data accuracy have been described in more detail elsewhere.4–7 Informed consent was obtained before beginning the interviews. The Human Subjects Committees of Okayama University (for the Okayama site), Japan NIMH (for the Kagoshima site), and Nagasaki University (for the Nagasaki site) approved the recruitment, consent, and field procedures.

Measures of suicide-related outcomes

Suicide-related outcomes were assessed using Version 3.0 of the WHO Composite International Diagnostic Interview (CIDI).8 The reliability and validity of the Japanese version have not been fully examined. A pilot study, however, using the Japanese version of WMH-CIDI with a small number of clinical psychiatric patients showed good concordance between clinical diagnosis and WMH-CIDI diagnosis of major depression and alcohol abuse/dependence.9 The WHO CIDI contains a module that assesses suicidal ideation (‘Have you ever seriously thought about committing suicide?’), suicide plans (‘Have you ever made a plan for committing suicide?’), and suicide attempts (‘Have you ever attempted suicide?’). Based on evidence that reports of such potentially embarrassing behaviors are higher in self-administered than interviewer-administered surveys,10 these questions were printed in a self-administered booklet and referred to by letter: A, ‘You seriously thought about committing suicide’; B, ‘You made a plan for committing suicide’; and C, ‘You attempted suicide’. An interviewer asked a respondent whether he/she had ‘a behavior indicated by A (or B, C)’, not mentioning the word ‘suicide’. Interviews assessed the lifetime presence and age-of-onset of each outcome.

Risk factors for suicide-related outcomes

The interviews also examined three sets of risk factors for suicide-related outcomes: sociodemographic factors, characteristics of suicide-related outcomes, and lifetime history of DSM-IV mood, anxiety, impulse-control, and substance use disorders. Characteristics of suicide-related outcomes included age of onset of ideation, time since onset of ideation, presence of suicide plan, and time since onset of plan.

Statistical analysis

Cross-tabulations were used to estimate lifetime prevalence of suicide-related outcomes. Discrete-time survival analyses with time-varying covariates11 were used to study retrospectively assessed sociodemographic and diagnostic correlates of first lifetime onset of each outcome based on retrospective age-of-onset reports. Survival coefficients were converted to odds ratios (OR) for ease of interpretation. The 95% confidence intervals (CI) of the OR were also reported and were adjusted for design effects. Continuous variables were divided into categories to minimize any effects of extreme values. Standard error (SE) and significance tests were estimated using the Taylor series method12 with SUDAAN13 software to adjust for the weighting and clustering of the data. Multivariate significance was evaluated using Wald χ2 tests based on design-corrected coefficient variance–covariance matrices. Statistical significance was evaluated using two-tailed 0.05-level tests.

RESULTS

  1. Top of page
  2. Abstract
  3. METHOD
  4. RESULTS
  5. DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES

Prevalence

The estimated lifetime prevalence (SE) of suicidal ideation, plans, and attempts in the overall sample was 10.9% (0.5), 2.1% (0.3), and 1.9% (0.3), respectively (Table 1). Among suicidal ideators, the conditional probability of ever making a suicide plan was 18.8% (2.6) and that of ever making a suicide attempt was 17.0% (2.5). The probability of an attempt among ideators with a plan was 52.1% (7.0) but only 8.8% (2.1) among those without a plan. Table 2 lists those for each location.

Table 1.  Lifetime prevalence of suicide-related outcomes: Japan
 Total sample (n = 2436)
IdeationPlanAttemptPlan among ideators (n = 264)Attempt among ideators (n = 264)Attempt among ideators without a lifetime plan (n = 214)Attempt among ideators with a lifetime plan (n = 50)
%SEn%SEn%SEn%SEn%SEn%SEn%SEn
Male10.61.01082.30.4251.70.41921.33.52515.93.4196.43.2650.96.413
Female11.20.71561.90.3252.00.42916.73.02517.83.42910.73.11553.410.914
Total Sample10.90.52642.10.3501.90.34818.82.65017.02.5488.82.12152.17.027
Table 2.  Lifetime prevalence of suicide-related outcomes by location
 Total Sample (n= 2436)
IdeationPlanAttempt
%SEn%SEn%SEn
Okayama11.70.71502.60.4332.30.529
Nagasaki17.81.4372.40.552.10.95
Kagoshima8.30.9801.30.4121.20.212

Sociodemographic factors

Risks of suicidal ideation and attempt were significantly higher in the most recent than in earlier age cohorts represented in the sample (χ2 = 15.8, P ≤ 0.01; χ2 = 19.0, P ≤ 0.01), and risk of suicide plan was significantly associated with a history of employment compared to never having been in the labor force (χ2 = 5.5, P ≤ 0.05; Table 3). Regarding age/cohort, the highest risk of both suicidal ideation and attempt was observed in the 35–49-years cohort (OR, 3.5; 95%CI: 1.8–6.7; OR, 68.1, 95%CI: 5.1–901.4), followed by the 20–34-years cohort (OR, 3.1, 95%CI: 1.5–6.6; OR, 37.7, 95%CI: 2.0–729.9), and 50–64-years cohort (OR, 2.2, 95%CI: 1.1–4.6; OR, 32.6, 95%CI: 2.4–452.1). The relationships between the sociodemographic risk factors and suicide-related outcomes were attenuated when predicting suicide plans and attempts among ideators, suggesting that the associations of these sociodemographic factors with suicide plans and attempts are largely mediated by suicidal ideation.

Table 3.  Sociodemographic risk factors for first onset of suicide-related outcomes: Japan
 Part II sample (n = 880)
IdeationPlanAttemptPlan Among ideators (n = 185)Attempt Among ideators (n = 185)Attempt Among ideators without a lifetime plan (n = 140)Attempt among ideators without a lifetime plan (n = 45)
SociodemographicSociodemographic categoryOR(95%CI)OR(95%CI)OR(95%CI)OR(95%CI)OR(95%CI)OR(95%CI)OR(95%CI)
  • *

    OR significant at the 0.05 level, two-sided test;

  • significant at the 0.05 level, two-sided test.

  • –, not used as a predictor in the model.

  • Results are based on multivariate discrete-time survival model with person-year as the unit of analysis.

  • Time intervals (INT) are used as a control, but in different form for the first three columns and the last four columns.

  • CI, confidence interval; OR, odds ratio

SexFemale1.0(0.6–1.6)0.9(0.4–1.7)1.1(0.5–2.3)0.7(0.3–1.6)0.6(0.1–2.2)2.3(0.5–9.8)0.7(0.1–3.6)
Male1.01.01.01.01.01.01.0
χ21[p]0.0[0.955]0.2[0.671]0.1[0.729]0.7[0.397]0.8[0.379]1.4[0.239]0.2[0.641]
Age group (years)20–343.1*(1.5–6.6)2.5(0.7–9.6)37.7*(2.0–729.9)1.0(0.2–4.7)21.5(0.7–699.9)3.7(0.6–23.3)0.1(0.0–3.0)
35–493.5*(1.8–6.7)3.2*(1.1–9.3)68.1*(5.1–901.4)1.2(0.3–4.9)38.3*(2.4–602.1)5.4*(1.4–21.5)0.2(0.0–2.3)
50–642.2*(1.1–4.6)1.3(0.5–3.5)32.6*(2.4–452.1)0.7(0.2–2.7)24.6*(1.6–385.6)1.01.0
65+1.01.01.01.01.01.01.0
χ23[p]15.8[0.001]6.7[0.083]19.0[<0.001]1.1[0.788]9.7[0.021]6.3[0.044]2.1[0.351]
EducationStudent2.0(0.5–8.5)2.8(0.4–18.8)1.7(0.2–15.0)0.5(0.0–4.6)0.4(0.0–10.1)0.0*(0.0–0.5)0.3(0.0–3.4)
Low1.4(0.5–4.3)0.8(0.3–1.9)1.8(0.3–10.2)0.4(0.1–2.3)2.3(0.1–40.9)0.3(0.0–2.9)0.4(0.0–9.4)
(Middle school or less)
Low/Medium1.4(0.6–3.2)0.6(0.2–1.6)1.4(0.3–7.2)0.3(0.1–1.8)2.1(0.1–32.8)0.1(0.0–3.2)12.2*(1.6–91.4)
(High school)
Medium1.0(0.5–2.4)0.2(0.0–1.3)1.1(0.2–6.4)0.2*(0.0–1.0)1.5(0.1–40.2)0.3(0.0–7.1)1.0
(Some college)
High1.01.01.01.01.01.01.0
(College or higher)
χ24[p]2.8[0.598]7.6[0.109]0.9[0.930]4.4[0.357]3.7[0.452]9.5[0.051]12.3[0.006]
EmploymentBefore first employment0.7(0.3–1.9)0.3*(0.1–0.9)0.6(0.2–1.9)0.5(0.2–1.4)0.4(0.1–1.6)0.5(0.1–4.1)2.4(0.2–33.3)
After first employment1.01.01.01.01.01.01.0
χ21[p]0.5[0.463]5.5[0.018]0.7[0.411]1.9[0.171]1.6[0.204]0.4[0.528]0.5[0.485]
MarriageBefore ever married1.1(0.6–2.1)1.7(0.4–6.9)3.5(0.7–16.9)1.7(0.4–7.1)2.3(0.2–23.4)1.9(0.2–20.5)0.2(0.0–4.0)
After ever married1.01.01.01.01.01.01.0
χ21[p]0.2[0.677]0.7[0.408]2.6[0.110]0.6[0.453]0.6[0.448]0.3[0.594]1.2[0.277]
Age onset of ideationEarly1.5(0.3–8.1)9.3(0.4–193.8)21.7(0.5–1021.3)108.9*(0.9–13835.6)
Middle1.0(0.2–4.1)1.8(0.1–28.2)1.7(0.1–29.6)35.0*(1.4–896.7)
Late1.01.01.01.0
χ22[p]0.3[0.866]4.6[0.102]4.1[0.129]5.0[0.080]
Time since onset of ideation0–1.170.1*(13.2–2189.4)390.2*(22.2–6870.6)122609.8*(18178.8–826962.9)
1–5.3.2(0.2–58.9)2.8(0.1–67.5)2.0(0.5–8.4)
6–10.3.0(0.2–50.4)1.4(0.1–29.8)1.0(0.4–2.4)
11+1.01.01.0
χ23[p]106.8[<0.001]76.3[<0.001]857.8[<0.001]
Having planYes32.7*(8.5–125.5)
No1.0
χ21[p]28.3[<0.001]
Time since onset of plan0–1.5157.8*(29.9–890647.9)
1–5.53.8*(1.5–1931.3)
6–10.8.3(0.1–637.4)
11+1.0
χ23[p]28.1[<0.001]

Characteristics of suicide-related outcomes as risk factors

Suicidal ideators were classified into terciles based on age of onset (AOO) of suicidal ideation to examine the relationship between AOO and risk of transition from ideation to plans and attempts. Analyses indicated that earlier AOO was associated with greater risk of suicide plan and attempt among subjects with suicidal ideation, although these associations were not statistically significant (Table 3). The transition from suicidal ideation to first onset of a suicide plan or attempt was highest within the first year of onset of ideation (OR, 170.1, 95%CI: 13.2–2189.4; OR, 390.2, 95%CI: 22.2–6870.6), and decreased substantially thereafter (3.2 of the plan in 1–5 yrs –1.4 of the attempt in 6–10 yrs). Having a suicide plan was associated with a significantly higher risk of ever making a suicide attempt among ideators (OR, 32.7 95%CI = 8.5−125.5), although the odds of making an attempt within the first year of onset of suicidal ideation were also high for those without a plan (i.e. impulsive suicide attempts, OR, 122 609.8, 95%CI: 18 178.8–826 962.9). Among attempters with a plan, the transition to a suicide attempt was highest within the first year of conceiving a plan (OR, 5157.8, 95%CI: 29.9–89 0647.9).

Mental disorders as risk factors

The presence of a prior mental disorder was associated with a significantly increased risk of a subsequent first onset of suicidal ideation, plans, and attempts, even after controlling for sociodemographic factors and characteristics of suicide-related outcomes (Table 4). Risk of suicide-related outcomes was greatest for mood disorders (ideation, OR, 5.5, 95%CI: 2.9–10.6; plan, OR, 6.9, 95%CI: 2.1–22.3; and attempt, OR, 19.4, 95%CI: 7.6–49.0), followed by substance use disorders (ideation, OR, 3.9, 95%CI: 1.8–8.2; plan, OR, 5.2, 95%CI: 1.7–16.1; and attempt, OR, 7.7, 95%CI: 2.5–23.7) and anxiety disorders (ideation, OR, 3.3, 95%CI: 1.8–5.9; plan, OR, 5.9, 95%CI: 2.6–13.2; and attempt, OR, 5.1, 95%CI: 2.6–10.1). Associations between mental disorders and suicide-related outcomes were attenuated when predicting plans and attempts among ideators, with OR decreasing to 0.9–8.5 across all categories, suggesting that the effects of mental disorders were largely on ideation. Among ideators, the risk of making an attempt was highest for subjects with mood disorders. The results also indicated a strong dose–response relationship between the number of mental disorders present and the risk of each suicide-related outcome.

Table 4.  DSM-IV Disorders as risk factors for first onset of suicide-related outcomes: Japan
DisorderPart II Sample (n = 880)
IdeationPlanAttemptPlan among ideators (n = 185)Attempt among ideators (n = 185)Attempt among ideators without a lifetime plan (n = 140)Attempt among ideators with a lifetime plan (n = 45)
OR(95%CI)OR(95%CI)OR(95%CI)OR(95%CI)OR(95%CI)OR(95%CI)OR(95%CI)
  • *

    OR significant at the 0.05 level, two-sided test.

  • Assessed in the Part II sample;

  • assessed only in the Part II sample for age range 18–44 years.

  • Each model controls for person-year, countries and the sociodemographic variables from the Table 2.

  • Any mood disorder, major depressive, dysthymic, and bipolar disorders; any impulse-control disorder, intermittent explosive, attention-deficit– hyperactivity, conduct, and oppositional defiant disorders; any anxiety disorder, panic, agoraphobia, generalized anxiety, specific phobia, social phobia, post-traumatic stress, obsessive–compulsive, and adult separation anxiety disorders; any substance use disorder, alcohol abuse or dependence and illicit drug abuse or dependence.

  • CI, confidence interval; OR, odds ratio.

Any anxiety disorders3.3*(1.8–5.9)5.9*(2.6–13.2)5.1*(2.6–10.1)2.2(0.7–7.4)0.9(0.2–4.1)1.6(0.2–12.3)2.4(0.5–13.1)
Any mood disorders5.5*(2.9–10.6)6.9*(2.1–22.3)19.4*(7.6–49.0)2.4(0.6–9.8)8.5*(2.4–29.8)6.9*(1.4–34.0)11.1(0.4–297.3)
Any impulse-control disorders
Any substance use disorders3.9*(1.8–8.2)5.2*(1.7–16.1)7.7*(2.5–23.7)1.9(0.4–10.2)2.0(0.4–8.9)13.8*(1.3–147.0)1.7(0.0–79.7)
Any disorders4.0*(2.6–6.1)5.2*(2.7–10.2)6.3*(2.6–15.1)1.8(0.6–5.3)2.0(0.5–8.6)3.4(0.6–18.8)1.0(0.2–4.0)
Exactly 1 disorder2.7*(1.6–4.6)1.9(0.6–6.2)2.0(0.6–6.7)0.9(0.2–3.3)0.9(0.2–4.8)1.2(0.2–6.2)0.1*(0.0–0.6)
Exactly 2 disorders3.7*(2.1–6.6)1.6(0.4–6.6)4.3*(1.0–18.5)0.5(0.1–2.7)1.7(0.2–16.3)2.3(0.3–19.6)0.7(0.0–36.7)
3+ disorders6.2*(3.5–10.8)23.4*(9.0–60.7)21.5*(10.1–45.9)12.2*(3.2–46.7)5.1*(1.0–25.4)9.0(0.5–161.3)10.2(0.7–142.4)

DISCUSSION

  1. Top of page
  2. Abstract
  3. METHOD
  4. RESULTS
  5. DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES

Study limitations

These findings should be interpreted in the context of several important limitations. First, the data were based on retrospective self-reporting of the occurrence and timing of suicide-related outcomes and mental disorders, and thus may be subject to underreporting and biased recall. We did not collect information from third-party informants to validate the respondents' reports. Counterbalancing concerns about the accuracy of these results are several systematic reviews that have demonstrated that adults can recall past experiences with sufficient accuracy to provide valuable information.14,15 Such data are especially useful, of course, when prospective data are not available,16 as in the present study.

Another noteworthy limitation is that several important mental disorders such as schizophrenia and personality disorders were not assessed in the WMH surveys because interview would have been difficult due to stigma and because previous validation studies showed that such disorders are overestimated in lay-administered interviews such as the CIDI,17 which was the case for psychotic disorders. This is unfortunate given that prior studies suggest that schizophrenia and suicide-related outcomes share unique prevalence patterns. A related limitation is that several types of non-suicidal self-injurious behavior, such as suicide gestures18 and self-mutilation,19 were not considered in the present study.

Risk factors of important suicide-related outcomes

Risks of suicidal ideation and attempt were significantly more common in the most recent than in earlier age cohorts represented in the sample, perhaps because suicidal elderly had already committed suicide and there was no real increase across generations. But a more likely reason for the increase was that the number who had actually completed suicide was quite small, and their omission would not explain trends as big as these. Another methodological possibility is that older people were more reluctant to admit suicidality, and that they lied more readily than younger people.

These limitations notwithstanding, these results provide valuable and previously unavailable information on the rates of non-lethal suicide-related outcomes in Japan. It is noteworthy that the 35–49-year age cohort and period after initial employment were risk factors in Japan, unlike previous reports from other countries that have indicated that female gender, young age, and social disadvantage are risk factors for suicide-related outcomes.20,21 Interestingly, the finding that being middle aged was a risk factor is consistent with the recent trend for the highest increase in the rate of suicide occurring among individuals in their 30s and 40s. According to statistics from the National Police Agency in Japan, for example, the most prominent increase in the rate of suicide has been seen among individuals in their 30s (an 8.6% increase compared with the previous year), followed by those in their 50s (7.3%) and 40s (3.7%) in 2002; and those in their 30s (17.0%), 40s (12.6%), and 20s (11.1%) in 2003.

Risk of suicide plans and attempts was also highest when suicidal ideation occurred at an earlier age and within the first year of ideation. A large number of transitions from ideation to plans and attempts occur within the first year of onset of ideation. No prior studies in Japan have examined the probability and speed of transition from ideation to plans and attempts, and this information can be especially useful to health-care providers working with potentially suicidal individuals. Another very important point to note for both clinical and scientific purposes is that the strong relationship observed between mental disorders and suicide plans and attempts diminished significantly when controlling for ideation. This suggests that factors beyond the mere presence of mental disorders explain the transition from ideation to plans and attempts. Severity of mental disorders could be critical in accounting for these transitions, along with other factors that are independent of mental disorders.

It has been suggested that more than 90% of those who die by suicide have a diagnosable mental disorder.22 The present findings indicate that mental disorders are as predictive of suicide-related outcomes as other factors examined here, and that comorbidity is an important predictor. Mood disorders were most predictive of suicide-related outcomes, as has been reported in prior studies.22,23

ACKNOWLEDGMENTS

  1. Top of page
  2. Abstract
  3. METHOD
  4. RESULTS
  5. DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES

The World Mental Health Surveys Japan was carried out in conjunction with the World Health Organization World Mental Health (WMH) Survey Initiative (http://www.hcp.med.harvard.edu/wmh/). These activities were supported by the United States National Institute of Mental Health (R01MH070884), the John D. and Catherine T. MacArthur Foundation, the Pfizer Foundation, the US Public Health Service (R13-MH066849, R01-MH069864, and R01 DA016558), the Fogarty International Center (FIRCA R01-TW006481), the Pan American Health Organization, Eli Lilly and Company, Ortho-McNeil Pharmaceutical, GlaxoSmithKline, and Bristol-Myers Squibb. The study was supported by grants from the Japan Ministry of Health, Labour, and Welfare (H13-SHOGAI-023, H14-TOKUBETSU-026, H16-KOKORO-013).

REFERENCES

  1. Top of page
  2. Abstract
  3. METHOD
  4. RESULTS
  5. DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES
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