Suicidal acts may cluster in time and space and lead to community concerns about further imitative suicidal episodes. Although suicide clusters have been researched in previous studies, less is known about the clustering of non-fatal suicidal behaviour (self-harm). Furthermore, most previous studies used crude temporal and spatial information, e.g., numbers aggregated by month and residence area, for cluster detection analysis. This study aimed to (i) identify space–time clusters of self-harm and suicide using daily incidence data and exact address and (ii) investigate the characteristics of cluster-related suicidal acts.

Data on emergency department presentations for self-harm and suicide deaths in Taipei City and New Taipei City, Taiwan, were used in this study. In all-age and age-specific analyses, self-harm and suicide clusters were identified using space–time permutation scan statistics. A cut-off of 0.10 for the p value was used to identify possible clusters. Logistic regression was used to investigate the characteristics associated with cluster-related episodes.

A total of 5,291 self-harm episodes and 1,406 suicides in Taipei City (2004–2006) and 20,531 self-harm episodes and 2,329 suicides in New Taipei City (2012–2016) were included in the analysis. In the two cities, two self-harm clusters (n [number of self-harm episodes or suicide deaths in the cluster] = 4 and 8 in Taipei City), four suicide clusters (n = 3 in Taipei City and n = 4, 11 and 4 in New Taipei City) and two self-harm and suicide combined clusters (n = 4 in Taipei City and n = 8 in New Taipei City) were identified. Space–time clusters of self-harm, suicide, and self-harm and suicide combined accounted for 0.05%, 0.59%, and 0.08% of the respective groups of suicidal acts. Cluster-related episodes of self-harm and suicide were more likely to be male (adjusted odds ratio [aOR] = 2.22, 95% confidence interval [CI] 1.26, 3.89) and young people aged 10–29 years (aOR = 2.72, 95% CI 1.43, 5.21) than their cluster-unrelated counterparts.

Space–time clusters of self-harm, suicide, and self-harm and suicide combined accounted for a relatively small proportion of suicidal acts and were associated with some sex/age characteristics. Focusing on suicide deaths alone may underestimate the size of some clusters and/or lead to some clusters being overlooked. Future research could consider combining self-harm and suicide data and use social connection information to investigate possible clusters of suicidal acts.

Youth suicide rates have increased markedly in some countries. This study aimed to estimate the population-attributable risk of psychiatric disorders associated with suicide among Taiwanese youth aged 10–24 years.

Data were obtained from the National Death Registry and National Health Insurance (NHI) claims database between 2007 and 2019. Youth who died by suicide were included, and comparisons, 1:10 matched by age and sex, were randomly selected from the Registry for NHI beneficiaries. We used multivariable logistic regression to estimate suicide odds ratios for psychiatric disorders. The population-attributable fractions (PAF) were calculated for each psychiatric disorder.

A total of 2345 youth suicide and 23 450 comparisons were included. Overall, 44.8% of suicides had a psychiatric disorder, while only 7.9% of the comparisons had a psychiatric disorder. The combined PAF for all psychiatric disorders was 55.9%. The top three psychiatric conditions of the largest PAFs were major depressive disorder, dysthymia, and sleep disorder. In the analysis stratified by sex, the combined PAF was 45.5% for males and 69.2% for females. The PAF among young adults aged 20–24 years (57.0%) was higher than among adolescents aged 10–19 years (48.0%).

Our findings of high PAF from major depressive disorder, dysthymia, and sleep disorder to youth suicides suggest that youth suicide prevention that focuses on detecting and treating mental illness may usefully target these disorders.

To investigate the spatial distribution of self-harm incidence rates, their socioeconomic correlates and sex/age differences using data on self-harm presentations to emergency departments from The Manchester Self-Harm Project (2003–2013).

Smoothed standardised incidence ratios for index self-harm episodes (n = 14 771) and their associations with area-level socioeconomic factors across 258 small areas (median population size = 1470) in the City of Manchester municipality were estimated using Bayesian hierarchical models.

Higher numbers and rates of self-harm were found in the north, east and far southern zones of the city, in contrast to below average rates in the city centre and the inner city zone to the south of the centre. Males and females aged 10–24, 25–44 and 45–64 years showed similar geographical patterning of self-harm. In contrast, there was no clear pattern in the group aged 65 years and older. Fully adjusted analyses showed a positive association of self-harm rates with the percentage of the unemployed population, households privately renting, population with limiting long-term illness and lone-parent households, and a negative association with the percentage of ethnicity other than White British and travel distance to the nearest hospital emergency department. The area-level characteristics investigated explained a large proportion (four-fifths) of the variability in area self-harm rates. Most associations were restricted to those aged under 65 years and some associations (e.g. with unemployment) were present only in the youngest age group.

The findings have implications for allocating prevention and intervention resources targeted at high-risk groups in high incidence areas. Targets for area-based interventions might include tackling the causes and consequences of joblessness, better treatment of long-term illness and consideration of the accessibility of health services.

Self-poisoning using pesticides is among the major methods of suicide worldwide, and accounts for one-fifth of suicides in 2006–2010 in South Korea. We investigated long-term trends in pesticide suicide rates in South Korea and factors related to these trends.

We calculated age-standardised rates of pesticide suicide in South Korea (1983–2014) using registered death data. We used graphical approach and joinpoint regression analysis to examine secular trends in pesticide suicide by sex, age and area, and a time-series analysis to investigate association of pesticide suicide rate with socioeconomic and agriculture-related factors. Age, period and cohort effects were examined using the intrinsic estimator method.

Age-standardised rate of pesticide suicide fluctuated between 1983 and 2000 before it markedly increased in 2000–2003 (annual percent change 29.7%), followed by a gradual fall (annual percent change −6.3%) in 2003–2011. Following the paraquat ban (2011–2012), there was a marked reduction (annual percent change −28.2%) in 2011–2014. Trend in pesticide suicide was associated with divorce rate but not with other factors studied. Declines in pesticide suicide in 2003–2011 were most noticeable in younger groups and metropolises; by contrast, elderly adults aged 70+ living in rural areas showed an upward trend until after the 2011–2012 paraquat ban, when it turned downward. In the age–period–cohort modelling, having been born between 1938 and 1947 was associated with higher pesticide suicide rates.

Pesticide suicide trend changed substantially in South Korea over the last three decades. Effective prevention should include close monitoring of trends and strong regulations of toxic pesticides.