# Self-harm and suicide death in the three years following hospitalization for intentional self-harm in adolescents and young adults: A nationwide study

Karine Goueslard, Catherine Quantin, Fabrice Jollant

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## To cite this version:

Karine Goueslard, Catherine Quantin, Fabrice Jollant. Self-harm and suicide death in the three years following hospitalization for intentional self-harm in adolescents and young adults: A nationwide study. Psychiatry Research, 2024, 334, 10.1016/j.psychres.2024.115807. hal-04615207

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# Self-harm and suicide death in the three years following hospitalization for intentional self-harm in adolescents and young adults: A nationwide study

<figure><img src="image_2.png" /></figure>

Karine Goueslard<sup>a</sup>, Catherine Quantin<sup>a,b,c</sup>, Fabrice Jollant<sup>d,e,f,g,h,*</sup>

## ARTICLE INFO

**Keywords:**

Suicidal behavior

Cohort

National

Young people

Repetition

Mortality

## ABSTRACT

Self-harm is frequent in youths. This study aimed to assess the risk of self-harm and mortality over a three-year period following self-harm hospitalization. Data were extracted from national databases in France. All patients aged 12 to 24 years and hospitalized for self-harm in 2013–2014 were included and compared to age- and sex-matched individuals with no self-harm hospitalization during this period. Cox proportional hazards regression models were used. Overall, 34,533 individuals were hospitalized for self-harm in 2013–2014 (70.8 % females, 79.6 % self-poisoning), with a peak among females aged 14–16. Comparison with 103,599 matched controls showed significantly higher rates of past self-harm, somatic and psychiatric disorders, and dispensed drugs in youth hospitalized for self-harm. During follow-up, they significantly more often repeated self-harm (20.9 vs. 0.1 %), died from any cause (0.6 vs 0.03 %) and from suicide (0.2 vs 0.01 %), particularly during the first year. The choice of a violent self-harm means at inclusion increased the risk of suicide during follow-up. Psychiatric disorders were a significant risk factor for all outcomes. In conclusion, at least one in five youths will self-harm, and one in two hundred will die in the three years following hospitalization for self-harm. Reinforced follow-up care is necessary in this population.

## 1. Introduction

According to the World Health Organization, more than 700,000 people die by suicide each year in the world and 10 to 20 times more people attempt suicide (World Health Organization 2019). Adolescence and young adulthood are particularly high-risk periods for intentional self-harming behaviors, with a peak of non-lethal self-harming acts in female adolescents in France and other countries (Vuagnat et al., 2019). A meta-analysis estimated a lifetime prevalence of self-harm in adolescents of 16.9 % with a mean age of 13 years old at onset (Gillies et al., 2018). Although suicide death in adolescents is much rarer than in older people, it is the second to fourth leading cause of death in this age group across the world (GBD 2021). While for many individuals non-lethal self-harm during adolescence is an isolated act with no long-term negative consequences, it has been globally associated with poorer

psychosocial outcomes in adulthood (Borschmann et al., 2017). Moreover, it is not uncommon that a self-harming act also reveals an undiagnosed mental disorder. Several major mental disorders emerge during adolescence and young adulthood (Whiteford et al., 2013), and mental disorders are significant risk factors for suicidal behaviors (Favril et al., 2022). For instance, adolescents and young adults hospitalized for a mental disorder have a risk of dying by suicide in the three following years that is multiplied by 9.2 when compared with the general population (Jollant et al., 2022). A comorbid mental disorder has also been associated with more unfavorable outcomes in those who self-harmed (Moran et al., 2012). Non-lethal self-harm during adolescence is therefore frequent and, for many individuals, an early sign of psychopathology with potentially unfavorable life trajectories.

Non-lethal self-harming behaviors are significant predictors of both repeated self-harm and death by suicide in the short- and longer-term

<footnote><sup>a</sup> Service de Biostatistiques et d'Information Médicale (DIM), CHU Dijon Bourgogne, France</footnote>

<footnote><sup>b</sup> Université de Bourgogne, CIC 1432, Module Épidémiologie Clinique, F21000 Dijon, France</footnote>

<footnote><sup>c</sup> Inserm, CESP, 94807, Villejuif, France</footnote>

<footnote><sup>d</sup> Department of psychiatry, Faculty of Medicine, Université Paris Saclay, Le Kremlin-Bicêtre, France</footnote>

<footnote><sup>e</sup> Department of psychiatry, Hopital Bicêtre, APHP, Le Kremlin-Bicêtre, France</footnote>

<footnote><sup>f</sup> Department of psychiatry, CHU Nîmes, Nîmes, France</footnote>

<footnote><sup>g</sup> McGill Group for Suicide Studies, Department of psychiatry, McGill University, Montréal, Québec, Canada</footnote>

<footnote><sup>h</sup> Moods Research Team, INSERM UMR-1178, CESP, Le Kremlin-Bicêtre, France</footnote>

<footnote>* Corresponding author: Dr Fabrice Jollant, Service de psychiatre, hôpital Bicêtre, 76 rue du général Leclerc 94270 Le Kremlin-Bicêtre, France.
E-mail address: Fabrice.jollant@universite-paris-saclay.fr (F. Jollant).</footnote>
<figure><img src="image_3.png" /></figure>

# Self-harm and suicide death in the three years following hospitalization for intentional self-harm in adolescents and young adults: A nationwide study

<figure><img src="image_4.png" /></figure>

Check for
updates

Karine Goueslard<sup>a</sup>, Catherine Quantin<sup>a,b,c</sup>, Fabrice Jollant<sup>d,e,f,g,h,*</sup>

## ARTICLE INFO

Keywords:

Suicidal behavior

Cohort

National

Young people

Repetition

Mortality

## ABSTRACT

Self-harm is frequent in youths. This study aimed to assess the risk of self-harm and mortality over a three-year period following self-harm hospitalization. Data were extracted from national databases in France. All patients aged 12 to 24 years and hospitalized for self-harm in 2013–2014 were included and compared to age- and sex-matched individuals with no self-harm hospitalization during this period. Cox proportional hazards regression models were used. Overall, 34,533 individuals were hospitalized for self-harm in 2013–2014 (70.8 % females, 79.6 % self-poisoning), with a peak among females aged 14–16. Comparison with 103,599 matched controls showed significantly higher rates of past self-harm, somatic and psychiatric disorders, and dispensed drugs in youth hospitalized for self-harm. During follow-up, they significantly more often repeated self-harm (20.9 vs. 0.1 %), died from any cause (0.6 vs 0.03 %) and from suicide (0.2 vs 0.01 %), particularly during the first year. The choice of a violent self-harm means at inclusion increased the risk of suicide during follow-up. Psychiatric disorders were a significant risk factor for all outcomes. In conclusion, at least one in five youths will self-harm, and one in two hundred will die in the three years following hospitalization for self-harm. Reinforced follow-up care is necessary in this population.

## 1. Introduction

According to the World Health Organization, more than 700,000 people die by suicide each year in the world and 10 to 20 times more people attempt suicide (World Health Organization 2019). Adolescence and young adulthood are particularly high-risk periods for intentional self-harming behaviors, with a peak of non-lethal self-harming acts in female adolescents in France and other countries (Vuagnat et al., 2019). A meta-analysis estimated a lifetime prevalence of self-harm in adolescents of 16.9 % with a mean age of 13 years old at onset (Gillies et al., 2018). Although suicide death in adolescents is much rarer than in older people, it is the second to fourth leading cause of death in this age group across the world (GBD 2021). While for many individuals non-lethal self-harm during adolescence is an isolated act with no long-term negative consequences, it has been globally associated with poorer

psychosocial outcomes in adulthood (Borschmann et al., 2017). Moreover, it is not uncommon that a self-harming act also reveals an undiagnosed mental disorder. Several major mental disorders emerge during adolescence and young adulthood (Whiteford et al., 2013), and mental disorders are significant risk factors for suicidal behaviors (Favril et al., 2022). For instance, adolescents and young adults hospitalized for a mental disorder have a risk of dying by suicide in the three following years that is multiplied by 9.2 when compared with the general population (Jollant et al., 2022). A comorbid mental disorder has also been associated with more unfavorable outcomes in those who self-harmed (Moran et al., 2012). Non-lethal self-harm during adolescence is therefore frequent and, for many individuals, an early sign of psychopathology with potentially unfavorable life trajectories.

Non-lethal self-harming behaviors are significant predictors of both repeated self-harm and death by suicide in the short- and longer-term

<footnote><sup>a</sup> Service de Biostatistiques et d'Information Médicale (DIM), CHU Dijon Bourgogne, France</footnote>

<footnote><sup>b</sup> Université de Bourgogne, CIC 1432, Module Épidémiologie Clinique, F21000 Dijon, France</footnote>

<footnote><sup>c</sup> Inserm, CESP, 94807, Villejuif, France</footnote>

<footnote><sup>d</sup> Department of psychiatry, Faculty of Medicine, Université Paris Saclay, Le Kremlin-Bicêtre, France</footnote>

<footnote><sup>e</sup> Department of psychiatry, Hopital Bicêtre, APHP, Le Kremlin-Bicêtre, France</footnote>

<footnote><sup>f</sup> Department of psychiatry, CHU Nîmes, Nîmes, France</footnote>

<footnote><sup>g</sup> McGill Group for Suicide Studies, Department of psychiatry, McGill University, Montréal, Québec, Canada</footnote>

<footnote><sup>h</sup> Moods Research Team, INSERM UMR-1178, CESP, Le Kremlin-Bicêtre, France</footnote>

<footnote>* Corresponding author: Dr Fabrice Jollant, Service de psychiatre, hôpital Bicêtre, 76 rue du général Leclerc 94270 Le Kremlin-Bicêtre, France.
E-mail address: Fabrice.jollant@universite-paris-saclay.fr (F. Jollant).</footnote>
(Suominen et al., 2004; Ribeiro et al., 2016; Favril et al., 2022). The risk of repeated self-harm and death by suicide in the year following self-harm hospitalization was estimated to be 16.3 % and 1.6 %, respectively, in a meta-analysis combining different age groups (Carroll et al., 2014). In a previous French study based on the same database as the present study, the overall risk of repeated self-harm and suicide in the year following self-harm hospitalization in 2008–2009 was 12.4 % and 0.9 %, respectively (Vuagnat et al., 2019). Regarding the high prevalence of non-lethal self-harming acts but the low prevalence of suicide mortality in young people, it is important to evaluate the risk of repeated self-harm and premature mortality specific to this age class since it may have organizational implications for the mental health system.

Several international studies published over the last decade have examined this question. A study conducted in 2001–2007 in 32,395 adolescents and young adults aged 12 to 24 from a Medicaid program in the USA found a standardized one-year suicide mortality rate of 46.0 (95 % CI 29.9–67.9) in adolescents and 19.2 (95 % CI 12.7–28.0) in young adults compared with the demographically-matched general population (Olsson et al., 2018). In this study, 17.1 % repeated non-fatal self-harm and 0.1 % died from suicide (with slightly higher rates in young adults than in adolescents) within the first year. A study in 20,471 Canadian youths aged 10–19 years old recruited between 2001 and 2012 and followed for about 7.2 years found a suicide mortality prevalence of 0.5 % overall and a suicide risk of 32.1 (95 % CI 23.6–43.6) in the year following intentional self-poisoning (Finkelstein et al., 2015). A study in the United Kingdom from a primary care database followed 16 912 patients aged 10–19 who self-harmed between 2001 and 2014 and showed that 21.5 % repeated non-fatal self-harm and 0.1 % died from suicide within 12 months (hazard ratio=17.5 (95 %CI 7.6–40.5)) (Morgan et al., 2017). The largest study to date retrospectively followed a cohort of 131,731 girls and 44 621 boys aged 10–19 for 10 years after discharge from British hospitals for self-harm between 1995 and 2016, reporting suicide rates of 0.2 % and 0.7 %, respectively (Herbert et al., 2017). Finally, the Multicenter Study of Self-Harm in England assessed 9173 individuals aged 10–19 who presented to the emergency department for self-harm between 2000 and 2013 and were followed-up for between 2 and 16 years; they reported a suicide rate of 0.6 % (Hawton et al., 2020). The same study in 5205 adolescents included between 2000 and 2007 reported a 27.3 % rate of non-fatal self-harm repetition over 2 to 6 years (Hawton et al., 2012b). Regarding mortality, it is interesting to note that suicide was not the cause of death in about half of young people with a history of self-harm (Finkelstein et al., 2015; Herbert et al., 2017; Morgan et al., 2017; Hawton et al., 2020).

The present study aims to investigate the risk of repetition of self-harm and mortality, notably due to suicide, in a large sample of young people, both adolescents and young adults. To this aim, we used data from the French national administrative health database to measure these two risks in the three years following hospitalization for self-harm in 2013–2014 in people aged 12–24 years old as compared to young people not hospitalized for self-harm. Secondary objectives were the identification of sociodemographic and clinical risk factors related to these two outcomes. The strengths of this study include the large sample size, the national and exhaustive coverage, a significant follow-up period, and the investigation of a country with a different health system than in the USA, UK and Canada, which have published most studies on this topic so far.

# 2. Methods

## 2.1. Data extraction

All data used here were extracted from the French national health data system (Système National des Données de Santé, SNDS), which covers 99 % of the French population (Bezin et al., 2017). From birth to death, it collects individual data for care consumption, including hospital

discharge abstracts (private and public hospitals), outpatient healthcare consultations, outpatient dispensed drugs, chronic disease compensation and specific causes of death.

Hospital diagnoses and chronic diseases are recorded using codes from the International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10). All data are pseudonymised.

The overall study period was 2008–2017. 2008 was chosen as it is considered the starting time of good-quality data from the SNDS and 2017 as it was the most recent year with available mortality data at the time of analyses. We then chose 2013–2014 for the inclusion period as a good compromise between a significant pre-inclusion period (2008–2012), a significant follow-up period (3 years for all participants) and a large number of participants over two years.

## 2.2. Subjects

All adolescents and young adults aged 12 to 24 years old who were hospitalized for an intentional self-harm between January 1st, 2013, and December 31st, 2014, were included in our study. They were identified from discharge abstracts, taking into account all ICD-10 codes X60-X84 recorded as primary or associated diagnoses. The first hospitalization identified during the study period with one of this code was considered as the index hospitalization. The group of included individuals was named "youths with self-harm hospitalization".

A control group of "youths without any self-harm hospitalization" was selected from the SNDS following a two-stage sample design. First, a sample of 5 % of French adolescents and young adults aged 12 to 24 years old was drawn. Then, we excluded individuals for whom a hospitalization for self-harm was recorded in discharge abstracts in 2013–2014. Lastly, we performed a second random draw in order to match for age and gender each case with three controls. We considered that "youths without any self-harm hospitalization" were all included in the study on January 1st, 2013. It should be noted that subjects in both groups may have been hospitalized for self-harm prior to 2013.

Each individual was followed during a fixed period of 3 years from the inclusion in our study. The maximum date of the observation period was therefore December 31st, 2017, for individuals included on December 31st, 2014.

## 2.3. Outcomes

The first outcome was the rate of hospitalization for intentional self-harm (at least one ICD-10 code X60 to X84) identified in any hospital discharge abstract (somatic or psychiatric in-patient care) in the three years following the index hospitalization or date of inclusion. The second outcome was the rate of all-cause and specific-cause mortality in the three years following the index hospitalization or date of inclusion. Mortality was classified in four categories: suicide, natural, accidental or undetermined causes.

## 2.4. Confounding variables

The additional following variables were extracted for all included individuals: age at index hospitalization (classified as 12–15, 16–17, 18–20, or 21–24 years), sex, means used for self-harm at index hospitalization, and a past history (since 2008) of hospitalization for self-harm, of physical diseases according to the main category systems (all chapters of ICD-10), psychiatric disorders (F10-F98 ICD-10 codes) and of reimbursed psychotropic drugs (according to the Anatomical Therapeutic Chemical (ATC) classification system N05, N06, N07B).

In "youths with self-harm hospitalization", the index self-harm was differentiated according to whether it used violent (hanging, drowning, firearm, fire and smoke, jumping, and vehicle collision) or nonviolent means (self-poisoning, sharp or blunt object, unspecified) as was done in previous work (Vuagnat et al., 2019).

During the follow-up period, the following information was
(Suominen et al., 2004; Ribeiro et al., 2016; Favril et al., 2022). The risk of repeated self-harm and death by suicide in the year following self-harm hospitalization was estimated to be 16.3 % and 1.6 %, respectively, in a meta-analysis combining different age groups (Carroll et al., 2014). In a previous French study based on the same database as the present study, the overall risk of repeated self-harm and suicide in the year following self-harm hospitalization in 2008–2009 was 12.4 % and 0.9 %, respectively (Vuagnat et al., 2019). Regarding the high prevalence of non-lethal self-harming acts but the low prevalence of suicide mortality in young people, it is important to evaluate the risk of repeated self-harm and premature mortality specific to this age class since it may have organizational implications for the mental health system.

Several international studies published over the last decade have examined this question. A study conducted in 2001–2007 in 32,395 adolescents and young adults aged 12 to 24 from a Medicaid program in the USA found a standardized one-year suicide mortality rate of 46.0 (95 % CI 29.9–67.9) in adolescents and 19.2 (95 % CI 12.7–28.0) in young adults compared with the demographically-matched general population (Olsson et al., 2018). In this study, 17.1 % repeated non-fatal self-harm and 0.1 % died from suicide (with slightly higher rates in young adults than in adolescents) within the first year. A study in 20,471 Canadian youths aged 10–19 years old recruited between 2001 and 2012 and followed for about 7.2 years found a suicide mortality prevalence of 0.5 % overall and a suicide risk of 32.1 (95 % CI 23.6–43.6) in the year following intentional self-poisoning (Finkelstein et al., 2015). A study in the United Kingdom from a primary care database followed 16 912 patients aged 10–19 who self-harmed between 2001 and 2014 and showed that 21.5 % repeated non-fatal self-harm and 0.1 % died from suicide within 12 months (hazard ratio=17.5 (95 %CI 7.6–40.5)) (Morgan et al., 2017). The largest study to date retrospectively followed a cohort of 131,731 girls and 44 621 boys aged 10–19 for 10 years after discharge from British hospitals for self-harm between 1995 and 2016, reporting suicide rates of 0.2 % and 0.7 %, respectively (Herbert et al., 2017). Finally, the Multicenter Study of Self-Harm in England assessed 9173 individuals aged 10–19 who presented to the emergency department for self-harm between 2000 and 2013 and were followed-up for between 2 and 16 years; they reported a suicide rate of 0.6 % (Hawton et al., 2020). The same study in 5205 adolescents included between 2000 and 2007 reported a 27.3 % rate of non-fatal self-harm repetition over 2 to 6 years (Hawton et al., 2012b). Regarding mortality, it is interesting to note that suicide was not the cause of death in about half of young people with a history of self-harm (Finkelstein et al., 2015; Herbert et al., 2017; Morgan et al., 2017; Hawton et al., 2020).

The present study aims to investigate the risk of repetition of self-harm and mortality, notably due to suicide, in a large sample of young people, both adolescents and young adults. To this aim, we used data from the French national administrative health database to measure these two risks in the three years following hospitalization for self-harm in 2013–2014 in people aged 12–24 years old as compared to young people not hospitalized for self-harm. Secondary objectives were the identification of sociodemographic and clinical risk factors related to these two outcomes. The strengths of this study include the large sample size, the national and exhaustive coverage, a significant follow-up period, and the investigation of a country with a different health system than in the USA, UK and Canada, which have published most studies on this topic so far.

# 2. Methods

## 2.1. Data extraction

All data used here were extracted from the French national health data system (Système National des Données de Santé, SNDS), which covers 99 % of the French population (Bezin et al., 2017). From birth to death, it collects individual data for care consumption, including hospital

discharge abstracts (private and public hospitals), outpatient healthcare consultations, outpatient dispensed drugs, chronic disease compensation and specific causes of death.

Hospital diagnoses and chronic diseases are recorded using codes from the International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10). All data are pseudonymised.

The overall study period was 2008–2017. 2008 was chosen as it is considered the starting time of good-quality data from the SNDS and 2017 as it was the most recent year with available mortality data at the time of analyses. We then chose 2013–2014 for the inclusion period as a good compromise between a significant pre-inclusion period (2008–2012), a significant follow-up period (3 years for all participants) and a large number of participants over two years.

## 2.2. Subjects

All adolescents and young adults aged 12 to 24 years old who were hospitalized for an intentional self-harm between January 1st, 2013, and December 31st, 2014, were included in our study. They were identified from discharge abstracts, taking into account all ICD-10 codes X60-X84 recorded as primary or associated diagnoses. The first hospitalization identified during the study period with one of this code was considered as the index hospitalization. The group of included individuals was named "youths with self-harm hospitalization".

A control group of "youths without any self-harm hospitalization" was selected from the SNDS following a two-stage sample design. First, a sample of 5 % of French adolescents and young adults aged 12 to 24 years old was drawn. Then, we excluded individuals for whom a hospitalization for self-harm was recorded in discharge abstracts in 2013–2014. Lastly, we performed a second random draw in order to match for age and gender each case with three controls. We considered that "youths without any self-harm hospitalization" were all included in the study on January 1st, 2013. It should be noted that subjects in both groups may have been hospitalized for self-harm prior to 2013.

Each individual was followed during a fixed period of 3 years from the inclusion in our study. The maximum date of the observation period was therefore December 31st, 2017, for individuals included on December 31st, 2014.

## 2.3. Outcomes

The first outcome was the rate of hospitalization for intentional self-harm (at least one ICD-10 code X60 to X84) identified in any hospital discharge abstract (somatic or psychiatric in-patient care) in the three years following the index hospitalization or date of inclusion. The second outcome was the rate of all-cause and specific-cause mortality in the three years following the index hospitalization or date of inclusion. Mortality was classified in four categories: suicide, natural, accidental or undetermined causes.

## 2.4. Confounding variables

The additional following variables were extracted for all included individuals: age at index hospitalization (classified as 12–15, 16–17, 18–20, or 21–24 years), sex, means used for self-harm at index hospitalization, and a past history (since 2008) of hospitalization for self-harm, of physical diseases according to the main category systems (all chapters of ICD-10), psychiatric disorders (F10-F98 ICD-10 codes) and of reimbursed psychotropic drugs (according to the Anatomical Therapeutic Chemical (ATC) classification system N05, N06, N07B).

In "youths with self-harm hospitalization", the index self-harm was differentiated according to whether it used violent (hanging, drowning, firearm, fire and smoke, jumping, and vehicle collision) or nonviolent means (self-poisoning, sharp or blunt object, unspecified) as was done in previous work (Vuagnat et al., 2019).

During the follow-up period, the following information was
extracted: death, cause of death when available (data only available between January 1, 2013, and December 31, 2015), a hospitalization for psychiatric or somatic disorders, means used for self-harm when it occurred, and reimbursed psychotropic drugs dispensed during ambulatory care.

## 2.5. Statistical analysis

Individual characteristics, physical and psychiatric comorbidities, and reimbursed psychotropic drugs are presented as proportions. Comparisons between the groups were first performed using Pearson χ2 tests or Fisher exact tests, as appropriate. In “youths with self-harm hospitalization”, the age distribution was explored. Monthly follow-up for the first year and then at 2 and 3 years following the index hospitalization for self-harm was also performed in all individuals, and in the specific group of adolescents aged 14 to 16 years according to gender due to previous studies showing a peak in the age distribution of self-harm in France in this age group in female adolescents (Vuagnat et al., 2019).

We also explored the time between the index hospitalization for self-harm in 2013–2014 and the first hospitalization for self-harm during follow-up, using Kaplan-Meier method to estimate median survival time.

To explore the association between being hospitalized for self-harm at inclusion and the occurrence of any self-harm hospitalization during the three-year follow-up, the main endpoint was the first occurrence of a subsequent hospitalization for self-harm. Thus, survival analyses were performed using a Cox proportional hazards regression model, after adjustment for confounding variables (age, sex, previous hospitalization for self-harm, for physical or psychiatric diseases, and previous psychotropic drug reimbursement). The same method was applied to explore the association between being hospitalized for self-harm at inclusion and all-cause death and death by suicide. In addition to matching for age and sex, we wanted to take into account these essential epidemiologic factors in terms of both self-harm (more often found in younger people and females) and suicide (more often found in older people and males). We therefore chose to include age and sex in the survival model to estimate the residual effect of these two factors, suggesting for example that there is still an effect of age on hospitalization for self-harm, despite matching for age at the year scale. We followed individuals until hospitalization for self-harm, death or the end of the follow-up period, whichever came first.

In “youths with self-harm hospitalization”, we also explored the risk of self-harm hospitalization during follow-up according to the type of self-harming means (violent or nonviolent) at the index hospitalization. Finally, we explored this risk according to the type of comorbid psychiatric disorders prior to the index hospitalization.

Lastly, we explored the risk of all-cause death and death by suicide according to any self-harm hospitalization during follow-up, and the risk of suicide according to the type of self-harming (violent/nonviolent) at the index hospitalization. A sensitivity analysis was performed according to the number of hospitalizations for self-harm.

The results are presented as adjusted hazard ratios (HR) and 95 % confidence intervals (CI). Statistical significance was set at a p value of 0.05 for all analyses. SAS 9.4 software was used for all data analyses.

# 3. Results

## 3.1. Description of the population

In France, 34,533 adolescents and young adults aged 12–24 years old were hospitalized for intentional self-harm at least once in 2013–2014. Among them, 24,453 were females (70.8 %). The most commonly used means were self-poisoning (79.6 %) and use of a sharp or blunt object (11.4 %), accounting for more than 90 % of acts.

The characteristics of adolescents and young adults hospitalized for self-harm in 2013–2014 and matched controls are presented in Table 1.

<caption>**Table 1**</caption>

Sociodemographic and clinical characteristics at inclusion, and self-harm hospitalization and mortality during the three years of follow-up in adolescents and young adults hospitalized for self-harm in 2013-2014, and in sex- and age-matched adolescents and young adults without any self-harm hospitalization in 2013-2014.

<table><thead><tr><th></th><th colspan="2">Youths with self-harm hospitalization (n=34,533)</th><th colspan="2">Youths without any self-harm hospitalization (n= 103,599)</th><th>p-value</th></tr><tr><th></th><th>n</th><th>%</th><th>n</th><th>%</th><th></th></tr></thead><tbody><tr><td><strong>Age (years)</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>12-15</td><td>10,396</td><td>30.1</td><td>31,188</td><td>30.1</td><td>1</td></tr><tr><td>16-17</td><td>6,914</td><td>20.0</td><td>20,742</td><td>20.0</td><td></td></tr><tr><td>18-20</td><td>7,879</td><td>22.8</td><td>23,637</td><td>22.8</td><td></td></tr><tr><td>21-24</td><td>9,344</td><td>27.1</td><td>28,032</td><td>27.1</td><td></td></tr><tr><td><strong>Sex</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Male</td><td>10,080</td><td>29.2</td><td>30,240</td><td>29.2</td><td>1</td></tr><tr><td>Female</td><td>24,453</td><td>70.8</td><td>73,359</td><td>70.8</td><td></td></tr><tr><td><strong>Means used for self-harm at index hospitalization</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Self-poisoning</td><td>27,482</td><td>79.6</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Hanging</td><td>754</td><td>2.2</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Drowning</td><td>68</td><td>0.2</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Firearms, explosive material</td><td>43</td><td>0.1</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Smoke, fire, steam</td><td>53</td><td>0.2</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Sharp or blunt object</td><td>3,927</td><td>11.4</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Jumping</td><td>517</td><td>1.5</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Crashing of motor vehicle</td><td>98</td><td>0.3</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Unspecified</td><td>1,591</td><td>4.6</td><td>-</td><td>-</td><td>-</td></tr><tr><td><strong>History (2008 to index hospitalization) of</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Hospitalization for physical diseases</td><td>31,746</td><td>91.9</td><td>13,370</td><td>12.9</td><td>&lt;0.0001</td></tr><tr><td>Hospitalization for psychiatric disorders</td><td>24,482</td><td>70.9</td><td>1,561</td><td>1.5</td><td>&lt;0.0001</td></tr><tr><td>Hospitalization for self-harm</td><td>3,297</td><td>9.6</td><td>348</td><td>0.3</td><td>&lt;0.0001</td></tr><tr><td>Psychotropic drugs as outpatients</td><td>11,001</td><td>31.9</td><td>3,140</td><td>3.0</td><td>&lt;0.0001</td></tr><tr><td><strong>Self-harm hospitalization during follow-up</strong></td><td>7,209</td><td>20.9</td><td>95</td><td>0.1</td><td>&lt;0.0001</td></tr><tr><td>Number of self-harming events</td><td>n=7,209</td><td></td><td>n=95</td><td></td><td></td></tr><tr><td>1</td><td>4,503</td><td>62.5</td><td>85</td><td>89.5</td><td>&lt;0.0001</td></tr><tr><td>2</td><td>1,268</td><td>17.6</td><td>6</td><td>6.3</td><td></td></tr><tr><td>3</td><td>555</td><td>7.7</td><td>2</td><td>2.1</td><td></td></tr><tr><td>≥4</td><td>883</td><td>12.2</td><td>2</td><td>2.1</td><td></td></tr><tr><td><strong>Means used for self-harm</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Self-poisoning</td><td>5,980</td><td>83.0</td><td>84</td><td>88.4</td><td>0.16</td></tr><tr><td>Hanging</td><td>281</td><td>3.9</td><td>3</td><td>3.2</td><td>0.71</td></tr><tr><td>Sharp or blunt object</td><td>1,610</td><td>22.3</td><td>9</td><td>9.5</td><td>0.003</td></tr><tr><td>Other self-harm methods</td><td>262</td><td>0.8</td><td>1</td><td>0.001</td><td>&lt;0.0001</td></tr><tr><td>Unspecified</td><td>513</td><td>7.1</td><td>5</td><td>5.3</td><td>0.48</td></tr><tr><td><strong>Mortality during follow-up</strong></td><td>200</td><td>0.6</td><td>53</td><td>0.05</td><td>&lt;0.0001</td></tr></tbody></table>

When a variable was not studied, the corresponding cells are shaded.

Notably, slightly more than 9 % of youths hospitalized for self-harm in 2013–2014 had a previous hospitalization for intentional self-harm, compared with only 0.3 % of youths who were not hospitalized for intentional self-harm in 2013–2014. Moreover, the two groups differed in terms of past medical history, with more hospitalizations for somatic and psychiatric disorders, and more psychotropic drug reimbursements in youths hospitalized for self-harm in 2013–2014 (Table 1).

Regarding age distribution by sex, as expected we observed a peak in the number of self-harm hospitalizations in females aged 15 (Fig. 1). In males, the increase was much slower and progressive, plateauing at around 17 years old. The female to male ratio in the number of self-harm hospitalizations ranged from 5.7 at 13 years to 1.2 at 24 years.

## 3.2. Hospitalization for intentional self-harm during the three years of follow-up

The rate of self-harm hospitalizations during follow-up was much higher in youths with an index hospitalization for self-harm (20.9 %) than in youths without any self-harm hospitalization in 2013–2014 (0.1 %).
extracted: death, cause of death when available (data only available between January 1, 2013, and December 31, 2015), a hospitalization for psychiatric or somatic disorders, means used for self-harm when it occurred, and reimbursed psychotropic drugs dispensed during ambulatory care.

## 2.5. Statistical analysis

Individual characteristics, physical and psychiatric comorbidities, and reimbursed psychotropic drugs are presented as proportions. Comparisons between the groups were first performed using Pearson χ2 tests or Fisher exact tests, as appropriate. In “youths with self-harm hospitalization”, the age distribution was explored. Monthly follow-up for the first year and then at 2 and 3 years following the index hospitalization for self-harm was also performed in all individuals, and in the specific group of adolescents aged 14 to 16 years according to gender due to previous studies showing a peak in the age distribution of self-harm in France in this age group in female adolescents (Vuagnat et al., 2019).

We also explored the time between the index hospitalization for self-harm in 2013–2014 and the first hospitalization for self-harm during follow-up, using Kaplan-Meier method to estimate median survival time.

To explore the association between being hospitalized for self-harm at inclusion and the occurrence of any self-harm hospitalization during the three-year follow-up, the main endpoint was the first occurrence of a subsequent hospitalization for self-harm. Thus, survival analyses were performed using a Cox proportional hazards regression model, after adjustment for confounding variables (age, sex, previous hospitalization for self-harm, for physical or psychiatric diseases, and previous psychotropic drug reimbursement). The same method was applied to explore the association between being hospitalized for self-harm at inclusion and all-cause death and death by suicide. In addition to matching for age and sex, we wanted to take into account these essential epidemiologic factors in terms of both self-harm (more often found in younger people and females) and suicide (more often found in older people and males). We therefore chose to include age and sex in the survival model to estimate the residual effect of these two factors, suggesting for example that there is still an effect of age on hospitalization for self-harm, despite matching for age at the year scale. We followed individuals until hospitalization for self-harm, death or the end of the follow-up period, whichever came first.

In “youths with self-harm hospitalization”, we also explored the risk of self-harm hospitalization during follow-up according to the type of self-harming means (violent or nonviolent) at the index hospitalization. Finally, we explored this risk according to the type of comorbid psychiatric disorders prior to the index hospitalization.

Lastly, we explored the risk of all-cause death and death by suicide according to any self-harm hospitalization during follow-up, and the risk of suicide according to the type of self-harming (violent/nonviolent) at the index hospitalization. A sensitivity analysis was performed according to the number of hospitalizations for self-harm.

The results are presented as adjusted hazard ratios (HR) and 95 % confidence intervals (CI). Statistical significance was set at a p value of 0.05 for all analyses. SAS 9.4 software was used for all data analyses.

# 3. Results

## 3.1. Description of the population

In France, 34,533 adolescents and young adults aged 12–24 years old were hospitalized for intentional self-harm at least once in 2013–2014. Among them, 24,453 were females (70.8 %). The most commonly used means were self-poisoning (79.6 %) and use of a sharp or blunt object (11.4 %), accounting for more than 90 % of acts.

The characteristics of adolescents and young adults hospitalized for self-harm in 2013–2014 and matched controls are presented in Table 1.

<caption>**Table 1**</caption>

Sociodemographic and clinical characteristics at inclusion, and self-harm hospitalization and mortality during the three years of follow-up in adolescents and young adults hospitalized for self-harm in 2013-2014, and in sex- and age-matched adolescents and young adults without any self-harm hospitalization in 2013-2014.

<table><thead><tr><th></th><th colspan="2">Youths with self-harm hospitalization (n=34,533)</th><th colspan="2">Youths without any self-harm hospitalization (n= 103,599)</th><th>p-value</th></tr><tr><th></th><th>n</th><th>%</th><th>n</th><th>%</th><th></th></tr></thead><tbody><tr><td><strong>Age (years)</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>12-15</td><td>10,396</td><td>30.1</td><td>31,188</td><td>30.1</td><td>1</td></tr><tr><td>16-17</td><td>6,914</td><td>20.0</td><td>20,742</td><td>20.0</td><td></td></tr><tr><td>18-20</td><td>7,879</td><td>22.8</td><td>23,637</td><td>22.8</td><td></td></tr><tr><td>21-24</td><td>9,344</td><td>27.1</td><td>28,032</td><td>27.1</td><td></td></tr><tr><td><strong>Sex</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Male</td><td>10,080</td><td>29.2</td><td>30,240</td><td>29.2</td><td>1</td></tr><tr><td>Female</td><td>24,453</td><td>70.8</td><td>73,359</td><td>70.8</td><td></td></tr><tr><td><strong>Means used for self-harm at index hospitalization</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Self-poisoning</td><td>27,482</td><td>79.6</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Hanging</td><td>754</td><td>2.2</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Drowning</td><td>68</td><td>0.2</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Firearms, explosive material</td><td>43</td><td>0.1</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Smoke, fire, steam</td><td>53</td><td>0.2</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Sharp or blunt object</td><td>3,927</td><td>11.4</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Jumping</td><td>517</td><td>1.5</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Crashing of motor vehicle</td><td>98</td><td>0.3</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Unspecified</td><td>1,591</td><td>4.6</td><td>-</td><td>-</td><td>-</td></tr><tr><td><strong>History (2008 to index hospitalization) of</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Hospitalization for physical diseases</td><td>31,746</td><td>91.9</td><td>13,370</td><td>12.9</td><td>&lt;0.0001</td></tr><tr><td>Hospitalization for psychiatric disorders</td><td>24,482</td><td>70.9</td><td>1,561</td><td>1.5</td><td>&lt;0.0001</td></tr><tr><td>Hospitalization for self-harm</td><td>3,297</td><td>9.6</td><td>348</td><td>0.3</td><td>&lt;0.0001</td></tr><tr><td>Psychotropic drugs as outpatients</td><td>11,001</td><td>31.9</td><td>3,140</td><td>3.0</td><td>&lt;0.0001</td></tr><tr><td><strong>Self-harm hospitalization during follow-up</strong></td><td>7,209</td><td>20.9</td><td>95</td><td>0.1</td><td>&lt;0.0001</td></tr><tr><td>Number of self-harming events</td><td>n=7,209</td><td></td><td>n=95</td><td></td><td></td></tr><tr><td>1</td><td>4,503</td><td>62.5</td><td>85</td><td>89.5</td><td>&lt;0.0001</td></tr><tr><td>2</td><td>1,268</td><td>17.6</td><td>6</td><td>6.3</td><td></td></tr><tr><td>3</td><td>555</td><td>7.7</td><td>2</td><td>2.1</td><td></td></tr><tr><td>≥4</td><td>883</td><td>12.2</td><td>2</td><td>2.1</td><td></td></tr><tr><td><strong>Means used for self-harm</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Self-poisoning</td><td>5,980</td><td>83.0</td><td>84</td><td>88.4</td><td>0.16</td></tr><tr><td>Hanging</td><td>281</td><td>3.9</td><td>3</td><td>3.2</td><td>0.71</td></tr><tr><td>Sharp or blunt object</td><td>1,610</td><td>22.3</td><td>9</td><td>9.5</td><td>0.003</td></tr><tr><td>Other self-harm methods</td><td>262</td><td>0.8</td><td>1</td><td>0.001</td><td>&lt;0.0001</td></tr><tr><td>Unspecified</td><td>513</td><td>7.1</td><td>5</td><td>5.3</td><td>0.48</td></tr><tr><td><strong>Mortality during follow-up</strong></td><td>200</td><td>0.6</td><td>53</td><td>0.05</td><td>&lt;0.0001</td></tr></tbody></table>

When a variable was not studied, the corresponding cells are shaded.

Notably, slightly more than 9 % of youths hospitalized for self-harm in 2013–2014 had a previous hospitalization for intentional self-harm, compared with only 0.3 % of youths who were not hospitalized for intentional self-harm in 2013–2014. Moreover, the two groups differed in terms of past medical history, with more hospitalizations for somatic and psychiatric disorders, and more psychotropic drug reimbursements in youths hospitalized for self-harm in 2013–2014 (Table 1).

Regarding age distribution by sex, as expected we observed a peak in the number of self-harm hospitalizations in females aged 15 (Fig. 1). In males, the increase was much slower and progressive, plateauing at around 17 years old. The female to male ratio in the number of self-harm hospitalizations ranged from 5.7 at 13 years to 1.2 at 24 years.

## 3.2. Hospitalization for intentional self-harm during the three years of follow-up

The rate of self-harm hospitalizations during follow-up was much higher in youths with an index hospitalization for self-harm (20.9 %) than in youths without any self-harm hospitalization in 2013–2014 (0.1 %).
<figure><img src="image_3.png" /><figcaption>Fig. 1. Age distribution by sex in adolescents and young adults hospitalized for self-harm in 2013–2014.</figcaption></figure>

%) (Table 1). Self-poisoning was the most frequent type of self-harm in both groups (83% vs. 88%). During follow-up, the number of self-harm events were also more frequent in those initially hospitalized for self-harm than among controls: 37.5 % self-harmed two times or more vs. 10.5 % in controls (Table 1).

We explored the time between the index hospitalization for self-harm in 2013–2014 and the first hospitalization for self-harm during follow-up, according to sex (Fig. 2) and age group. We found a median survival time of 114 days [108–122] in “youths with self-harm hospitalization” group, 98.5 days in males [90–111] and 121 days in females [112–128]. Among youths who had self-harm hospitalizations during the first year after the index hospitalization for self-harm, one third were re-hospitalized during the first month.

Among youths hospitalized for self-harm in 2013–2014, the monthly self-harm hospitalization rates for the 12 months before and after the index hospitalization were low in both males and females in the preceding year but high during the first month (6.15 %) followed by

decreasing trend. The overall readmission rate in the population of youths hospitalized for self-harm was estimated at 20.9% during the three years of follow-up.

Considering the higher number of self-harm events among 14–16-year-old females, we focused on this particular age group. Among 8931 girls and 2069 boys aged 14–16 years old at the index hospitalization for self-harm in 2013–2014, 22.3 % of girls and 18.6 % of boys had at least one additional hospitalization for self-harm during the three years of follow-up. We found similar rates and trends in boys and girls for the three years before and after the index hospitalization for self-harm (Supplemental Figures 1 and 2). More than three quarters were re-hospitalized during the first year, notably the first month, and less than 10 % were re-hospitalized 2 years or more after the index hospitalization. The median time between the index hospitalization for self-harm and the first hospitalization for self-harm during follow-up was 125 days [112–137] for 14–16-year-old females and 104 days [80–144] for 14–16-year-old males.

<figure><img src="image_4.png" /><figcaption>Fig. 2. Monthly hospitalization rates for self-harm in the 12 months before and after the index hospitalization for self-harm in 2013–2014 (vertical line), in females and males.</figcaption></figure>
<figure><img src="image_5.png" /><figcaption>Fig. 1. Age distribution by sex in adolescents and young adults hospitalized for self-harm in 2013–2014.</figcaption></figure>

%) (Table 1). Self-poisoning was the most frequent type of self-harm in both groups (83% vs. 88%). During follow-up, the number of self-harm events were also more frequent in those initially hospitalized for self-harm than among controls: 37.5 % self-harmed two times or more vs. 10.5 % in controls (Table 1).

We explored the time between the index hospitalization for self-harm in 2013–2014 and the first hospitalization for self-harm during follow-up, according to sex (Fig. 2) and age group. We found a median survival time of 114 days [108–122] in “youths with self-harm hospitalization” group, 98.5 days in males [90–111] and 121 days in females [112–128]. Among youths who had self-harm hospitalizations during the first year after the index hospitalization for self-harm, one third were re-hospitalized during the first month.

Among youths hospitalized for self-harm in 2013–2014, the monthly self-harm hospitalization rates for the 12 months before and after the index hospitalization were low in both males and females in the preceding year but high during the first month (6.15 %) followed by

decreasing trend. The overall readmission rate in the population of youths hospitalized for self-harm was estimated at 20.9% during the three years of follow-up.

Considering the higher number of self-harm events among 14–16-year-old females, we focused on this particular age group. Among 8931 girls and 2069 boys aged 14–16 years old at the index hospitalization for self-harm in 2013–2014, 22.3 % of girls and 18.6 % of boys had at least one additional hospitalization for self-harm during the three years of follow-up. We found similar rates and trends in boys and girls for the three years before and after the index hospitalization for self-harm (Supplemental Figures 1 and 2). More than three quarters were re-hospitalized during the first year, notably the first month, and less than 10 % were re-hospitalized 2 years or more after the index hospitalization. The median time between the index hospitalization for self-harm and the first hospitalization for self-harm during follow-up was 125 days [112–137] for 14–16-year-old females and 104 days [80–144] for 14–16-year-old males.

<figure><img src="image_6.png" /><figcaption>Fig. 2. Monthly hospitalization rates for self-harm in the 12 months before and after the index hospitalization for self-harm in 2013–2014 (vertical line), in females and males.</figcaption></figure>
A hospitalization for self-harm was significantly associated with an increased risk of subsequent self-harm hospitalization during the three years of follow-up (Table 2). After adjustment for age, sex, a history of hospitalization for somatic or psychiatric disorders, of self-harm, and psychotropic drug reimbursement, the risk of repeated hospitalization for self-harm remained highly significant (HR 74.4; 95 % CI 59.55–92.94). Moreover, being female, being younger, having a history of hospitalization for a psychiatric disorder or for self-harm, or a past history of psychotropic drug reimbursement were also significantly associated with an increased risk of subsequent hospitalization for self-harm. The findings were similar when the index hospitalization was differentiated according to violent or nonviolent means of self-harm, respectively HR 76.0 (95 % CI 59.6–97.0) and HR 74.2 (95 % CI 59.4–92.7). We also explored the risk associated with the type of psychiatric conditions identified before the index hospitalization (Supplementary Table 1). Most of the psychiatric disorders studied were significantly associated with a repeated hospitalization for self-harm, with limited differences between disorders.

### 3.3. Mortality during the three years of follow-up

In youths hospitalized for self-harm in 2013–2014, 200 deaths (0.6 %) occurred during follow-up versus 53 (0.03 %) among youths with no hospitalization for self-harm (Table 1).

The median time between the index hospitalization for self-harm in 2013–2014 and death was 349 days.

Without adjustment, hospitalization for self-harm was significantly associated with a higher mortality from all causes during follow-up (Table 3). After adjustment for age, sex, history of hospitalization for somatic disorders, psychiatric disorders, and self-harm, and history of psychotropic drug reimbursement, this association remained significant (HR=3.83; CI 2.25–6.53). A history of hospitalization for psychiatric disorders or of psychotropic drugs reimbursement significantly increased the risk of all-cause death during follow-up. Moreover, this risk increased with age and was increased in males.

Rates of suicide were 0.2 % in those hospitalized for self-harm in 2013–2014 (0.2 % in females, 0.5 % in males) vs. 0.01 % (0.01 % in females, 0.02 % in males) in those not hospitalized for self-harm during the same period (p<0.0001) (Table 1). Among those for whom the cause of death could be identified, suicide accounted for 51.3 % of all deaths among youths hospitalized for self-harm in 2013–2014 compared to 18.8 % in youths without any hospitalization for self-harm (Table 1).

After adjustment, the risk of suicide during the three years of follow-up was increased in case of hospitalization for self-harm at inclusion (HR=12.20; CI 4.28–34.76) (Table 4).

<caption>**Table 3**</caption>

Estimated risk of all-cause death during the three years of follow-up in adolescents and young adults hospitalized for self-harm in 2013–2014, in comparison to sex- and age-matched adolescents and young adults without any self-harm hospitalization in 2013–2014.

<table><thead><tr><th rowspan="2"></th><th colspan="2">Crude</th><th colspan="2">Multivariable model</th></tr><tr><th>HR</th><th>95%CI</th><th>HR</th><th>95%CI</th></tr></thead><tbody><tr><td>Hospitalization for self-harm at inclusion (ref=0)</td><td>11.35</td><td>8.39–15.37</td><td>3.83</td><td>2.25–6.53</td></tr><tr><td>History of hospitalization for</td><td></td><td></td><td></td><td></td></tr><tr><td>Somatic diseases (ref=0)</td><td>7.99</td><td>5.89–10.83</td><td>1.51</td><td>0.97–2.35</td></tr><tr><td>Psychiatric disorders (ref=0)</td><td>9.87</td><td>7.55–12.90</td><td>1.83</td><td>1.23–2.73</td></tr><tr><td>Self-harm (ref=0)</td><td>6.76</td><td>4.80–9.51</td><td>1.39</td><td>0.97–2.00</td></tr><tr><td>History of psychotropic drug reimbursement (ref=0)</td><td>8.07</td><td>6.31–10.32</td><td>1.91</td><td>1.43–2.55</td></tr><tr><td>Female (ref=male)</td><td>0.31</td><td>0.24–0.40</td><td>0.39</td><td>0.30–0.50</td></tr><tr><td>Age (years) (ref=14–15)</td><td></td><td></td><td></td><td></td></tr><tr><td>16–17</td><td>2.55</td><td>1.52–4.27</td><td>2.14</td><td>1.27–3.58</td></tr><tr><td>18–20</td><td>3.50</td><td>2.17–5.66</td><td>2.51</td><td>1.54–4.07</td></tr><tr><td>21–24</td><td>6.30</td><td>4.04–9.81</td><td>3.80</td><td>2.41–5.99</td></tr></tbody></table>

HR: Hazard Ratio; CI= Confidence Intervals.

An increased risk was additionally associated with being male, older and in those with a history of psychiatric disorders.

Finally, we explored the association between the type of self-harm (violent/nonviolent) that led to the index hospitalization and subsequent suicide. During the three years follow-up, there were 12 suicides (0.8 %) in case of violent means, and 70 suicides (0.2 %) in case of non-violent means. While both groups were significantly associated with a higher risk of subsequent suicide without adjustment, only use of a violent means for the index self-harm remained significantly associated with subsequent death by suicide after adjustment for age, sex, history of hospitalization for somatic diseases, psychiatric disorders, and self-harm and history of psychotropic drug reimbursement (HR 3.51 [1.88–6.58]).

### 4. Discussion

In summary, 20.9 % of adolescents and young adults aged 12 to 24 years who were hospitalized for intentional self-harm in 2013–2014 in France were readmitted to hospital for self-harm during the following three years, mainly in the first year. This is well above the rate observed on a sex- and age-matched sample of youths who had no hospitalization for self-harm in 2013–2014 (0.1 %). The adjusted hazard ratio for

<caption>**Table 2**</caption>

Estimated risk of self-harm hospitalization during the three years of follow-up in adolescents and young adults with a hospitalization for self-harm in 2013–2014, in comparison to sex- and age-matched adolescents and young adults without any self-harm hospitalization in 2013–2014.

<table><caption>**Table 4**</caption><thead><tr><th rowspan="2"></th><th colspan="2">Crude</th><th colspan="2">Multivariable model</th></tr><tr><th>HR</th><th>95%CI</th><th>HR</th><th>95%CI</th></tr></thead><tbody><tr><td>Hospitalization for self-harm at inclusion (ref=0)</td><td>255.82</td><td>208.94–313.21</td><td>74.40</td><td>59.55–92.94</td></tr><tr><td>History of hospitalization for</td><td></td><td></td><td></td><td></td></tr><tr><td>Somatic disorders (ref=0)</td><td>21.75</td><td>20.10–23.54</td><td>1.07</td><td>0.99–1.17</td></tr><tr><td>Psychiatric disorders (ref=0)</td><td>38.73</td><td>36.03–41.63</td><td>3.41</td><td>3.16–3.69</td></tr><tr><td>Self-harm (ref=0)</td><td>9.56</td><td>9.01–10.15</td><td>1.66</td><td>1.56–1.76</td></tr><tr><td>History of psychotropic drug reimbursement (ref=0)</td><td>8.79</td><td>8.39–9.20</td><td>1.71</td><td>1.62–1.80</td></tr><tr><td>Female (ref=0)</td><td>1.12</td><td>1.07–1.18</td><td>1.16</td><td>1.10–1.22</td></tr><tr><td>Age (years) : Ref=14–15</td><td></td><td></td><td></td><td></td></tr><tr><td>16–17</td><td>0.85</td><td>0.79–0.91</td><td>0.77</td><td>0.72–0.82</td></tr><tr><td>18–20</td><td>0.81</td><td>0.76–0.86</td><td>0.69</td><td>0.65–0.74</td></tr><tr><td>21–24</td><td>0.93</td><td>0.88–0.99</td><td>0.71</td><td>0.67–0.76</td></tr></tbody></table>

Estimated risk of suicide during the three years of follow-up in adolescents and young adults with self-harm hospitalization in 2013–2014, in comparison to sex- and age-matched adolescents and young adults without self-harm hospitalization in 2013–2014.

<table><thead><tr><th rowspan="2"></th><th colspan="2">Crude</th><th colspan="2">Multivariable Model</th></tr><tr><th>HR</th><th>CI</th><th>HR</th><th>CI</th></tr></thead><tbody><tr><td>Hospitalization for self-harm at inclusion (ref=0)</td><td>27.40</td><td>13.77–54.53</td><td>12.20</td><td>4.28–34.76</td></tr><tr><td>History of hospitalization for</td><td></td><td></td><td></td><td></td></tr><tr><td>Somatic disorders (ref=0)</td><td>9.68</td><td>5.64–16.61</td><td>0.84</td><td>0.43–1.64</td></tr><tr><td>Psychiatric disorders (ref=0)</td><td>18.79</td><td>11.09–31.82</td><td>2.62</td><td>1.29–5.33</td></tr><tr><td>Self-harm (ref=0)</td><td>5.63</td><td>3.07–10.33</td><td>1.02</td><td>0.54–1.92</td></tr><tr><td>History of psychotropic drug reimbursement (ref=0)</td><td>8.60</td><td>5.70–12.98</td><td>1.55</td><td>0.98–2.43</td></tr><tr><td>Female (ref=male)</td><td>0.32</td><td>0.21–0.49</td><td>0.45</td><td>0.29–0.68</td></tr><tr><td>Age (years) (ref=14–15)</td><td></td><td></td><td></td><td></td></tr><tr><td>16–17</td><td>1.72</td><td>0.62–4.74</td><td>1.52</td><td>0.55–4.20</td></tr><tr><td>18–20</td><td>4.53</td><td>1.95–10.51</td><td>3.51</td><td>1.50–8.21</td></tr><tr><td>21–24</td><td>8.27</td><td>3.76–18.21</td><td>5.65</td><td>2.51–12.68</td></tr></tbody></table>

HR: Hazard Ratio; CI=95 % Confidence Intervals.
A hospitalization for self-harm was significantly associated with an increased risk of subsequent self-harm hospitalization during the three years of follow-up (Table 2). After adjustment for age, sex, a history of hospitalization for somatic or psychiatric disorders, of self-harm, and psychotropic drug reimbursement, the risk of repeated hospitalization for self-harm remained highly significant (HR 74.4; 95 % CI 59.55–92.94). Moreover, being female, being younger, having a history of hospitalization for a psychiatric disorder or for self-harm, or a past history of psychotropic drug reimbursement were also significantly associated with an increased risk of subsequent hospitalization for self-harm. The findings were similar when the index hospitalization was differentiated according to violent or nonviolent means of self-harm, respectively HR 76.0 (95 % CI 59.6–97.0) and HR 74.2 (95 % CI 59.4–92.7). We also explored the risk associated with the type of psychiatric conditions identified before the index hospitalization (Supplementary Table 1). Most of the psychiatric disorders studied were significantly associated with a repeated hospitalization for self-harm, with limited differences between disorders.

### 3.3. Mortality during the three years of follow-up

In youths hospitalized for self-harm in 2013–2014, 200 deaths (0.6 %) occurred during follow-up versus 53 (0.03 %) among youths with no hospitalization for self-harm (Table 1).

The median time between the index hospitalization for self-harm in 2013–2014 and death was 349 days.

Without adjustment, hospitalization for self-harm was significantly associated with a higher mortality from all causes during follow-up (Table 3). After adjustment for age, sex, history of hospitalization for somatic disorders, psychiatric disorders, and self-harm, and history of psychotropic drug reimbursement, this association remained significant (HR=3.83; CI 2.25–6.53). A history of hospitalization for psychiatric disorders or of psychotropic drugs reimbursement significantly increased the risk of all-cause death during follow-up. Moreover, this risk increased with age and was increased in males.

Rates of suicide were 0.2 % in those hospitalized for self-harm in 2013–2014 (0.2 % in females, 0.5 % in males) vs. 0.01 % (0.01 % in females, 0.02 % in males) in those not hospitalized for self-harm during the same period (p<0.0001) (Table 1). Among those for whom the cause of death could be identified, suicide accounted for 51.3 % of all deaths among youths hospitalized for self-harm in 2013–2014 compared to 18.8 % in youths without any hospitalization for self-harm (Table 1).

After adjustment, the risk of suicide during the three years of follow-up was increased in case of hospitalization for self-harm at inclusion (HR=12.20; CI 4.28–34.76) (Table 4).

<caption>**Table 3**</caption>

Estimated risk of all-cause death during the three years of follow-up in adolescents and young adults hospitalized for self-harm in 2013–2014, in comparison to sex- and age-matched adolescents and young adults without any self-harm hospitalization in 2013–2014.

<table><thead><tr><th rowspan="2"></th><th colspan="2">Crude</th><th colspan="2">Multivariable model</th></tr><tr><th>HR</th><th>95%CI</th><th>HR</th><th>95%CI</th></tr></thead><tbody><tr><td>Hospitalization for self-harm at inclusion (ref=0)</td><td>11.35</td><td>8.39–15.37</td><td>3.83</td><td>2.25–6.53</td></tr><tr><td>History of hospitalization for</td><td></td><td></td><td></td><td></td></tr><tr><td>Somatic diseases (ref=0)</td><td>7.99</td><td>5.89–10.83</td><td>1.51</td><td>0.97–2.35</td></tr><tr><td>Psychiatric disorders (ref=0)</td><td>9.87</td><td>7.55–12.90</td><td>1.83</td><td>1.23–2.73</td></tr><tr><td>Self-harm (ref=0)</td><td>6.76</td><td>4.80–9.51</td><td>1.39</td><td>0.97–2.00</td></tr><tr><td>History of psychotropic drug reimbursement (ref=0)</td><td>8.07</td><td>6.31–10.32</td><td>1.91</td><td>1.43–2.55</td></tr><tr><td>Female (ref=male)</td><td>0.31</td><td>0.24–0.40</td><td>0.39</td><td>0.30–0.50</td></tr><tr><td>Age (years) (ref=14–15)</td><td></td><td></td><td></td><td></td></tr><tr><td>16–17</td><td>2.55</td><td>1.52–4.27</td><td>2.14</td><td>1.27–3.58</td></tr><tr><td>18–20</td><td>3.50</td><td>2.17–5.66</td><td>2.51</td><td>1.54–4.07</td></tr><tr><td>21–24</td><td>6.30</td><td>4.04–9.81</td><td>3.80</td><td>2.41–5.99</td></tr></tbody></table>

HR: Hazard Ratio; CI= Confidence Intervals.

Finally, we explored the association between the type of self-harm (violent/nonviolent) that led to the index hospitalization and subsequent suicide. During the three years follow-up, there were 12 suicides (0.8 %) in case of violent means, and 70 suicides (0.2 %) in case of non-violent means. While both groups were significantly associated with a higher risk of subsequent suicide without adjustment, only use of a violent means for the index self-harm remained significantly associated with subsequent death by suicide after adjustment for age, sex, history of hospitalization for somatic diseases, psychiatric disorders, and self-harm and history of psychotropic drug reimbursement (HR 3.51 [1.88–6.58]).

### 4. Discussion

In summary, 20.9 % of adolescents and young adults aged 12 to 24 years who were hospitalized for intentional self-harm in 2013–2014 in France were readmitted to hospital for self-harm during the following three years, mainly in the first year. This is well above the rate observed on a sex- and age-matched sample of youths who had no hospitalization for self-harm in 2013–2014 (0.1 %). The adjusted hazard ratio for

<caption>**Table 2**</caption>

Estimated risk of self-harm hospitalization during the three years of follow-up in adolescents and young adults with a hospitalization for self-harm in 2013–2014, in comparison to sex- and age-matched adolescents and young adults without any self-harm hospitalization in 2013–2014.

<table><caption>**Table 4**</caption><thead><tr><th rowspan="2"></th><th colspan="2">Crude</th><th colspan="2">Multivariable model</th></tr><tr><th>HR</th><th>95%CI</th><th>HR</th><th>95%CI</th></tr></thead><tbody><tr><td>Hospitalization for self-harm at inclusion (ref=0)</td><td>255.82</td><td>208.94–313.21</td><td>74.40</td><td>59.55–92.94</td></tr><tr><td>History of hospitalization for</td><td></td><td></td><td></td><td></td></tr><tr><td>Somatic disorders (ref=0)</td><td>21.75</td><td>20.10–23.54</td><td>1.07</td><td>0.99–1.17</td></tr><tr><td>Psychiatric disorders (ref=0)</td><td>38.73</td><td>36.03–41.63</td><td>3.41</td><td>3.16–3.69</td></tr><tr><td>Self-harm (ref=0)</td><td>9.56</td><td>9.01–10.15</td><td>1.66</td><td>1.56–1.76</td></tr><tr><td>History of psychotropic drug reimbursement (ref=0)</td><td>8.79</td><td>8.39–9.20</td><td>1.71</td><td>1.62–1.80</td></tr><tr><td>Female (ref=0)</td><td>1.12</td><td>1.07–1.18</td><td>1.16</td><td>1.10–1.22</td></tr><tr><td>Age (years) : Ref=14–15</td><td></td><td></td><td></td><td></td></tr><tr><td>16–17</td><td>0.85</td><td>0.79–0.91</td><td>0.77</td><td>0.72–0.82</td></tr><tr><td>18–20</td><td>0.81</td><td>0.76–0.86</td><td>0.69</td><td>0.65–0.74</td></tr><tr><td>21–24</td><td>0.93</td><td>0.88–0.99</td><td>0.71</td><td>0.67–0.76</td></tr></tbody></table>

Estimated risk of suicide during the three years of follow-up in adolescents and young adults with self-harm hospitalization in 2013–2014, in comparison to sex- and age-matched adolescents and young adults without self-harm hospitalization in 2013–2014.

<table><thead><tr><th rowspan="2"></th><th colspan="2">Crude</th><th colspan="2">Multivariable Model</th></tr><tr><th>HR</th><th>CI</th><th>HR</th><th>CI</th></tr></thead><tbody><tr><td>Hospitalization for self-harm at inclusion (ref=0)</td><td>27.40</td><td>13.77–54.53</td><td>12.20</td><td>4.28–34.76</td></tr><tr><td>History of hospitalization for</td><td></td><td></td><td></td><td></td></tr><tr><td>Somatic disorders (ref=0)</td><td>9.68</td><td>5.64–16.61</td><td>0.84</td><td>0.43–1.64</td></tr><tr><td>Psychiatric disorders (ref=0)</td><td>18.79</td><td>11.09–31.82</td><td>2.62</td><td>1.29–5.33</td></tr><tr><td>Self-harm (ref=0)</td><td>5.63</td><td>3.07–10.33</td><td>1.02</td><td>0.54–1.92</td></tr><tr><td>History of psychotropic drug reimbursement (ref=0)</td><td>8.60</td><td>5.70–12.98</td><td>1.55</td><td>0.98–2.43</td></tr><tr><td>Female (ref=male)</td><td>0.32</td><td>0.21–0.49</td><td>0.45</td><td>0.29–0.68</td></tr><tr><td>Age (years) (ref=14–15)</td><td></td><td></td><td></td><td></td></tr><tr><td>16–17</td><td>1.72</td><td>0.62–4.74</td><td>1.52</td><td>0.55–4.20</td></tr><tr><td>18–20</td><td>4.53</td><td>1.95–10.51</td><td>3.51</td><td>1.50–8.21</td></tr><tr><td>21–24</td><td>8.27</td><td>3.76–18.21</td><td>5.65</td><td>2.51–12.68</td></tr></tbody></table>

HR: Hazard Ratio; CI=95 % Confidence Intervals.
repeated self-harm reached 74.4. Moreover, hospitalization for intentional self-harm was associated with increased mortality during follow-up, both overall (0.6 vs 0.03 %) and by suicide (0.2 vs 0.01 %). The corresponding hazard ratios were 3.8 and 12.2. Youths hospitalized for self-harm also showed significantly higher rates of past self-harm, psychiatric and somatic disorders, and dispensed psychotropic drugs. Beyond self-harm hospitalization, age, sex, and a comorbid mental disorder remained significant risk factors for all outcomes. Youths who self-harm therefore appear to be a vulnerable population that deserves careful attention to prevent risky behaviors and premature mortality.

Before discussing our findings, we must acknowledge several limitations. First, we only studied self-harming acts resulting in hospitalization, leading to an underestimation of the phenomenon. One French study from a phone survey in a representative sample of the general adult population showed that 40 % of declared suicide attempts were not followed by presentation to a hospital, with increasing rates in younger people (Jollant et al., 2020). However, it is likely that the most severe self-harming acts or those with more severe psychopathology result in hospital admission. Second, somatic and psychiatric comorbidities were diagnosed based on hospital abstracts only, and the quality of these diagnoses cannot always be guaranteed. Moreover, less severe disorders that did not require hospitalization are missing from the database. We therefore used psychotropic drug dispensing as a proxy to outpatient care. Third, some data relevant to the understanding of self-harm is not available in the health system databases, including social environment and support, early developmental history, motives for self-harm and suicidal intent.

The rate of repeated hospitalization for self-harm found in the present study (20.9 %) is consistent with rates found in previous studies in adolescents (Hawton et al., 2012a; Morgan et al., 2017; Olfson et al., 2018). It is however slightly higher than findings from a meta-analysis of 78 studies in all ages (16.3 % [15.1–17.7] at 1 year) (Carroll et al., 2014), and higher than a previous study in France in 2008–2009, again in all age groups (12.4 %) (Vuagnat et al., 2019). Rates of repetition in adolescents and young adults may therefore be higher than in older adults. Interestingly, we actually observed a significant age effect even within this limited age class, with younger people attempting more often. One-third of self-harm repetition occurred during the first month, and three-quarters occurred during the first year, emphasizing the need for improved prevention and care during this post-hospitalization period. Furthermore, we found classical risk factors for repeated self-harm, notably being a female and being younger. Previous studies have shown that earlier onset of suicidal and non-suicidal self-harm increased the frequency of self-harm episodes, over the following year and lifetime (Ammerman et al., 2018; Muehlenkamp et al., 2019; Brager-Larsen et al., 2022). Examination of the subgroup of 14–16-year-old females - a group with a particularly high number of self-harm hospitalizations - showed a slightly increased risk of repetition (22.3 %) compared to the overall study population. This risk was lower in males of the same age (18.6 %), as previously reported (Madge et al., 2011).

The reasons for which 14–16-year-old females display this intriguing and concerning very high level of self-harm and repeated self-harm could not be explored here. A survey in Scotland found that self-harm in 15–16-year-old girls was associated with physical abuse, serious problems with boys, self-harm by friends, and low level of optimism, in addition to other non-gender-specific risk factors such as bullying, issues with sexual orientation, self-harm in family and anxiety (O’Connor et al. 2009). Female-specific risk factors for suicide attempts were explored in a meta-analysis of longitudinal studies in adolescents and young adults, which also identified particular adverse events such as experiencing dating violence, interpersonal problems and previous abortion (Miranda-Mendizabal et al., 2019). Adolescence was also found to increase the risk of self-harm (Goueslard et al., 2023). A combination of interpersonal and sexual events and contagion effects in a time of increased peer interactions (in addition to the emergence of mental disorders) may therefore contribute to this high level of self-harm in young female

adolescents.

Hospitalization for self-harm was also associated with an increased risk of mortality (0.6 %), even in this young age group. Among our cases, 0.2 % died from suicide, with additional causes of death being natural and accidents. Again, this is within the range of recent large studies in adolescents and young adults mentioned in the introduction (Finkelstein et al., 2015; Herbert et al., 2017; Morgan et al., 2017; Olfson et al., 2018; Hawton et al., 2020) after taking into account different follow-up periods. As expected, the corresponding rate was higher in the meta-analysis mentioned above (1.6 % at one year) as it included all age groups combined (Carroll et al., 2014). We also reported higher all-cause mortality and suicide-related mortality in males than in females and in older individuals, even in the limited age range of our population.

In agreement with previous studies (Tidemalm et al., 2015; Vuagnat et al., 2019), suicide mortality during follow-up was higher in those whose had used a violent means for a previous non-lethal self-harm. It has been suggested that the choice of a violent means, a major contributor to a fatal outcome in self-harm, may be associated with particular clinical, biological and cognitive characteristics, including higher sensation-seeking, impaired decision-making, a particular genetic profile, and lower functioning of the serotonergic system (Asberg et al., 1976; Perrain et al., 2020; Lübbert et al., 2022). It may be relevant to offer reinforced follow-up and define specific care in the subgroup of people who self-harm with a violent means. In any case, this subject warrants more research.

One last observation is the significant role of mental disorders beyond self-harm. Patients who self-harmed had a higher rate of past hospitalization for mental disorders and/or dispensed psychotropic drugs. Moreover, mental disorders remained significantly associated with repeated self-harm, all-cause mortality and suicide mortality in multivariable regression analyses. Previous studies in adolescents who self-harmed showed more unfavorable outcomes in case of comorbid mental disorders, including higher risk of repetition during adulthood (Moran et al., 2012). In a previous study using a similar methodology and investigating the three years following hospitalization for a mental disorder in youths, we reported hazard ratios of 105.5, 13.3 and 9.2 of repeated self-harm, all-cause mortality and suicide (Jollant et al., 2022). Self-harm may be a red flag for the diagnosis of mental disorder. The current challenges in child and adolescent psychiatry in France with a major shortage of child psychiatrists is worrisome in this regard.

In terms of practice and policy to prevent self-harm repetition and premature mortality in young people, robust evidence remains scarce. In a recent Cochrane review of interventions for self-harm in adolescents, Witt et al. (Witt et al., 2021) identified 17 trials, all investigating psychosocial interventions and none about pharmacological interventions. Only dialectic behavioral therapy was found to reduce self-harm repetition in adolescents compared to treatment-as-usual or enhanced care in four trials. However, the quality of evidence was found to be low overall. School-based mental health and awareness programs have also shown some effects on the reduction of suicide attempts and suicidal ideation (Zalsman et al., 2016). The identification of effective interventions to prevent self-harm in this age group is critically needed. Potential targets of intervention include the prevention of contagion effects notably through social media; addressing issues related to sexual orientation and gender identity; fighting school bullying and sexual violence; promoting help-seeking behaviors, and fostering self-esteem and resilience; the development of peer gatekeeper programs; facilitated access to information and care, including crisis centers; and the early identification and adequate treatment of mental disorders (Hawton et al., 2012c). Moreover, restricting access to the various means of suicide is a demonstrated method to prevent death (Zalsman et al., 2016). Considering the scope of the problem, there is an urgent need for large-scale studies, with robust outcomes including repeated self-harm and mortality, as well as social functioning and mental disorder remission.

In conclusion, our study, based on national data in 2013–2014 with a
repeated self-harm reached 74.4. Moreover, hospitalization for intentional self-harm was associated with increased mortality during follow-up, both overall (0.6 vs 0.03 %) and by suicide (0.2 vs 0.01 %). The corresponding hazard ratios were 3.8 and 12.2. Youths hospitalized for self-harm also showed significantly higher rates of past self-harm, psychiatric and somatic disorders, and dispensed psychotropic drugs. Beyond self-harm hospitalization, age, sex, and a comorbid mental disorder remained significant risk factors for all outcomes. Youths who self-harm therefore appear to be a vulnerable population that deserves careful attention to prevent risky behaviors and premature mortality.

Before discussing our findings, we must acknowledge several limitations. First, we only studied self-harming acts resulting in hospitalization, leading to an underestimation of the phenomenon. One French study from a phone survey in a representative sample of the general adult population showed that 40 % of declared suicide attempts were not followed by presentation to a hospital, with increasing rates in younger people (Jollant et al., 2020). However, it is likely that the most severe self-harming acts or those with more severe psychopathology result in hospital admission. Second, somatic and psychiatric comorbidities were diagnosed based on hospital abstracts only, and the quality of these diagnoses cannot always be guaranteed. Moreover, less severe disorders that did not require hospitalization are missing from the database. We therefore used psychotropic drug dispensing as a proxy to outpatient care. Third, some data relevant to the understanding of self-harm is not available in the health system databases, including social environment and support, early developmental history, motives for self-harm and suicidal intent.

The rate of repeated hospitalization for self-harm found in the present study (20.9 %) is consistent with rates found in previous studies in adolescents (Hawton et al., 2012a; Morgan et al., 2017; Olfson et al., 2018). It is however slightly higher than findings from a meta-analysis of 78 studies in all ages (16.3 % [15.1–17.7] at 1 year) (Carroll et al., 2014), and higher than a previous study in France in 2008–2009, again in all age groups (12.4 %) (Vuagnat et al., 2019). Rates of repetition in adolescents and young adults may therefore be higher than in older adults. Interestingly, we actually observed a significant age effect even within this limited age class, with younger people attempting more often. One-third of self-harm repetition occurred during the first month, and three-quarters occurred during the first year, emphasizing the need for improved prevention and care during this post-hospitalization period. Furthermore, we found classical risk factors for repeated self-harm, notably being a female and being younger. Previous studies have shown that earlier onset of suicidal and non-suicidal self-harm increased the frequency of self-harm episodes, over the following year and lifetime (Ammerman et al., 2018; Muehlenkamp et al., 2019; Brager-Larsen et al., 2022). Examination of the subgroup of 14–16-year-old females - a group with a particularly high number of self-harm hospitalizations - showed a slightly increased risk of repetition (22.3 %) compared to the overall study population. This risk was lower in males of the same age (18.6 %), as previously reported (Madge et al., 2011).

The reasons for which 14–16-year-old females display this intriguing and concerning very high level of self-harm and repeated self-harm could not be explored here. A survey in Scotland found that self-harm in 15–16-year-old girls was associated with physical abuse, serious problems with boys, self-harm by friends, and low level of optimism, in addition to other non-gender-specific risk factors such as bullying, issues with sexual orientation, self-harm in family and anxiety (O’Connor et al. 2009). Female-specific risk factors for suicide attempts were explored in a meta-analysis of longitudinal studies in adolescents and young adults, which also identified particular adverse events such as experiencing dating violence, interpersonal problems and previous abortion (Miranda-Mendizabal et al., 2019). Adolescence was also found to increase the risk of self-harm (Goueslard et al., 2023). A combination of interpersonal and sexual events and contagion effects in a time of increased peer interactions (in addition to the emergence of mental disorders) may therefore contribute to this high level of self-harm in young female

adolescents.

Hospitalization for self-harm was also associated with an increased risk of mortality (0.6 %), even in this young age group. Among our cases, 0.2 % died from suicide, with additional causes of death being natural and accidents. Again, this is within the range of recent large studies in adolescents and young adults mentioned in the introduction (Finkelstein et al., 2015; Herbert et al., 2017; Morgan et al., 2017; Olfson et al., 2018; Hawton et al., 2020) after taking into account different follow-up periods. As expected, the corresponding rate was higher in the meta-analysis mentioned above (1.6 % at one year) as it included all age groups combined (Carroll et al., 2014). We also reported higher all-cause mortality and suicide-related mortality in males than in females and in older individuals, even in the limited age range of our population.

In agreement with previous studies (Tidemalm et al., 2015; Vuagnat et al., 2019), suicide mortality during follow-up was higher in those whose had used a violent means for a previous non-lethal self-harm. It has been suggested that the choice of a violent means, a major contributor to a fatal outcome in self-harm, may be associated with particular clinical, biological and cognitive characteristics, including higher sensation-seeking, impaired decision-making, a particular genetic profile, and lower functioning of the serotonergic system (Asberg et al., 1976; Perrain et al., 2020; Lübbert et al., 2022). It may be relevant to offer reinforced follow-up and define specific care in the subgroup of people who self-harm with a violent means. In any case, this subject warrants more research.

One last observation is the significant role of mental disorders beyond self-harm. Patients who self-harmed had a higher rate of past hospitalization for mental disorders and/or dispensed psychotropic drugs. Moreover, mental disorders remained significantly associated with repeated self-harm, all-cause mortality and suicide mortality in multivariable regression analyses. Previous studies in adolescents who self-harmed showed more unfavorable outcomes in case of comorbid mental disorders, including higher risk of repetition during adulthood (Moran et al., 2012). In a previous study using a similar methodology and investigating the three years following hospitalization for a mental disorder in youths, we reported hazard ratios of 105.5, 13.3 and 9.2 of repeated self-harm, all-cause mortality and suicide (Jollant et al., 2022). Self-harm may be a red flag for the diagnosis of mental disorder. The current challenges in child and adolescent psychiatry in France with a major shortage of child psychiatrists is worrisome in this regard.

In terms of practice and policy to prevent self-harm repetition and premature mortality in young people, robust evidence remains scarce. In a recent Cochrane review of interventions for self-harm in adolescents, Witt et al. (Witt et al., 2021) identified 17 trials, all investigating psychosocial interventions and none about pharmacological interventions. Only dialectic behavioral therapy was found to reduce self-harm repetition in adolescents compared to treatment-as-usual or enhanced care in four trials. However, the quality of evidence was found to be low overall. School-based mental health and awareness programs have also shown some effects on the reduction of suicide attempts and suicidal ideation (Zalsman et al., 2016). The identification of effective interventions to prevent self-harm in this age group is critically needed. Potential targets of intervention include the prevention of contagion effects notably through social media; addressing issues related to sexual orientation and gender identity; fighting school bullying and sexual violence; promoting help-seeking behaviors, and fostering self-esteem and resilience; the development of peer gatekeeper programs; facilitated access to information and care, including crisis centers; and the early identification and adequate treatment of mental disorders (Hawton et al., 2012c). Moreover, restricting access to the various means of suicide is a demonstrated method to prevent death (Zalsman et al., 2016). Considering the scope of the problem, there is an urgent need for large-scale studies, with robust outcomes including repeated self-harm and mortality, as well as social functioning and mental disorder remission.

In conclusion, our study, based on national data in 2013–2014 with a
significant follow-up period of 3 years, confirms the high rates of repeated self-harm and mortality in adolescents and young adults hospitalized for self-harm. One fifth exhibited repeated self-harming behaviors, usually in the short-term, and one in two hundred died at a young age, from suicide but also other causes. Research on both the mechanisms of self-harm in youths and individual and collective intervention strategies should be a national priority.

### CRediT authorship contribution statement

**Karine Goueslard:** Conceptualization, Formal analysis, Writing – original draft, Writing – review & editing. **Catherine Quantin:** Conceptualization, Funding acquisition, Supervision, Writing – review & editing. **Fabrice Jollant:** Conceptualization, Funding acquisition, Supervision, Writing – original draft, Writing – review & editing.

### Declaration of competing interest

All authors declare no conflict of interest.

This study was funded by a grant from the French Ministry of Health, Department of statistics (*Direction de la recherche, des études, de l'évaluation et des statistiques, DREES*) in 2018 to CQ and FJ.

### Acknowledgment

The authors want to thank Mrs Gwenaelle Periard for her help with manuscript editing and Mrs Suzanne Rankin for language editing.

### Supplementary materials

Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.psychres.2024.115807.

### References

Ammerman, B.A., Jacobucci, R., Kleiman, E.M., Uyeji, L.L., McCloskey, M.S., 2018. The relationship between nonsuicidal self-injury age of onset and severity of self-harm. Suicide Life Threat. Behav. 48, 31–37.

Asberg, M., Traskman, L., Thoren, P., 1976. 5-HIAA in the cerebrospinal fluid. A biochemical suicide predictor? Arch. Gen. Psychiatry 33, 1193–1197.

Bezin, J., Duong, M., Lassalle, R., Droz, G., Pariente, A., Blin, P., Moore, N., 2017. The national healthcare system claims databases in France, SNIRAM and EGB: powerful tools for pharmacoepidemiology. Pharmacoepidemiol. Drug Saf. 26, 954–962.

Borschmann, R., Becker, D., Coffey, C., Spry, E., Moreno-Betancur, M., Moran, P., Patton, G.C., 2017. 20-year outcomes in adolescents who self-harm: a population-based cohort study. Lancet Child Adolesc. Health 1, 195–202.

Brager-Larsen, A., Zeiner, P., Klungsøyr, O., Mehlum, L., 2022. Is age of self-harm onset associated with increased frequency of non-suicidal self-injury and suicide attempts in adolescent outpatients. BMC Psychiatry 22, 58.

Carroll, R., Metcalfe, C., Gunnell, D., 2014. Hospital presenting self-harm and risk of fatal and non-fatal repetition: systematic review and meta-analysis. PLoS. One 9, e89944.

Favril, L., Yu, R., Uyar, A., Sharpe, M., Fazel, S., 2022. Risk factors for suicide in adults: systematic review and meta-analysis of psychological autopsy studies. Evid. Based. Ment. Health 25, 148–155.

Finkelstein, Y., Macdonald, E.M., Hollands, S., Hutson, J.R., Sivilotti, M.L., Mamdani, M. M., Koren, G., Juurlink, D.N., Canadian Drug Safety and Effectiveness Research Network, C.D.S.E.R.N., 2015. Long-term outcomes following self-poisoning in adolescents: a population-based cohort study. Lancet Psychiatry 2, 532–539.

GBD, A.M.C., 2021. Global, regional, and national mortality among young people aged 10-24 years, 1950-2019: a systematic analysis for the Global Burden of Disease Study 2019. Lancet 398, 1593–1618.

Gillies, D., Christou, M.A., Dixon, A.C., Featherston, O.J., Rapti, I., Garcia-Anguita, A., Villasenor, M., Reebye, P., Christou, E., Al Kabir, N., Christou, P.A., 2018. Prevalence and characteristics of self-harm in adolescents: meta-analyses of community-based studies 1990-2015. J. Am. Acad. Child Adolesc. Psychiatry 57, 733–741.

Goueslard, K., Jollant, F., Cottenet, J., Bechraoui-Quantin, S., Rozenberg, P., Simon, E., Quantin, C., 2023. Hospitalization for non-lethal self-harm and premature mortality in the three years following adolescent pregnancy: population-based nationwide cohort study. BJOG.

Hawton, K., Bale, L., Brand, F., Townsend, E., Ness, J., Waters, K., Clements, C., Kapur, N., Geulayov, G., 2020. Mortality in children and adolescents following

presentation to hospital after non-fatal self-harm in the Multicentre Study of Self-harm: a prospective observational cohort study. Lancet Child Adolesc. Health 4, 111–120.

Hawton, K., Bergen, H., Kapur, N., Cooper, J., Steeg, S., Ness, J., Waters, K., 2012a. Repetition of self-harm and suicide following self-harm in children and adolescents: findings from the multicentre study of self-harm in England. J. Child Psychol. Psychiatry 53, 1212–1219.

Hawton, K., Bergen, H., Waters, K., Ness, J., Cooper, J., Steeg, S., Kapur, N., 2012b. Epidemiology and nature of self-harm in children and adolescents: findings from the multicentre study of self-harm in England. Eur. Child Adolesc. Psychiatry 21, 369–377.

Hawton, K., Saunders, K.E., O'Connor, R.C., 2012c. Self-harm and suicide in adolescents. Lancet 379, 2373–2382.

Herbert, A., Gilbert, R., Cottrell, D., Li, L., 2017. Causes of death up to 10 years after admissions to hospitals for self-inflicted, drug-related or alcohol-related, or violent injury during adolescence: a retrospective, nationwide, cohort study. Lancet 390, 577–587.

Jollant, F., Goueslard, K., Hawton, K., Quantin, C., 2022. Self-harm, somatic disorders and mortality in the 3 years following a hospitalisation in psychiatry in adolescents and young adults. Evid. Based Ment. Health ebmental-2021.

Jollant, F., Hawton, K., Vaiva, G., Chan-Chee, C., du Roscoat, E., Leon, C., 2020. Non-presentation at hospital following a suicide attempt: a national survey. Psychol. Med. 1–8.

Lübbert, M., Bahlmann, L., Sobanski, T., Schulz, A., Kastner, U.W., Walter, M., Jollant, F., Wagner, G., 2022. Investigating the clinical profile of suicide attempters who used a violent suicidal means. J. Clin. Med. 11, 7170.

Madge, N., Hawton, K., McMahon, E.M., Corcoran, P., De Leo, D., de Wilde, E.J., Fekete, S., van Heeringen, K., Ystgaard, M., Arensman, E., 2011. Psychological characteristics, stressful life events and deliberate self-harm: findings from the Child & Adolescent Self-harm in Europe (CASE) Study. Eur. Child Adolesc. Psychiatry 20, 499–508.

Miranda-Mendizabal, A., Castellví, P., Parés-Badell, O., Alayo, I., Almenara, J., Alonso, I., Blasco, M.J., Cebrià, A., Gabilondo, A., Gili, M., Lagares, C., Piqueras, J.A., Rodríguez-Jiménez, T., Rodríguez-Marín, J., Roca, M., Soto-Sanz, V., Vilagut, G., Alonso, J., 2019. Gender differences in suicidal behavior in adolescents and young adults: systematic review and meta-analysis of longitudinal studies. Int. J. Public Health 64, 265–283.

Moran, P., Coffey, C., Romaniuk, H., Olsson, C., Borschmann, R., Carlin, J.B., Patton, G. C., 2012. The natural history of self-harm from adolescence to young adulthood: a population-based cohort study. Lancet 379, 236–243.

Morgan, C., Webb, R.T., Carr, M.J., Kontopantelis, E., Green, J., Chew-Graham, C.A., Kapur, N., Ashcroft, D.M., 2017. Incidence, clinical management, and mortality risk following self harm among children and adolescents: cohort study in primary care. BMJ 359, j4351.

Muehlenkamp, J.J., Xhunga, N., Brausch, A.M., 2019. Self-injury age of onset: a risk factor for NSSI severity and suicidal behavior. Arch. Suicide Res. 23, 551–563.

O'Connor, R.C., Rasmussen, S., Miles, J., Hawton, K., 2009. Self-harm in adolescents: self-report survey in schools in Scotland. Br. J. Psychiatry 194, 68–72.

Olsson, M., Wall, M., Wang, S., Crystal, S., Bridge, J.A., Liu, S.M., Blanco, C., 2018. Suicide after deliberate self-harm in adolescents and young adults. Pediatrics.

Perrain, R., Dardennes, R., Jollant, F., 2020. Risky decision-making in suicide attempters, and the choice of a violent suicidal means: an updated meta-analysis. J. Affect. Disord. 280, 241–249.

Ribeiro, J.D., Franklin, J.C., Fox, K.R., Bentley, K.H., Kleiman, E.M., Chang, B.P., Nock, M.K., 2016. Self-injurious thoughts and behaviors as risk factors for future suicide ideation, attempts, and death: a meta-analysis of longitudinal studies. Psychol. Med. 46, 225–236.

Suominen, K., Isometsä, E., Suokas, J., Haukka, J., Achte, K., Lonnqvist, J., 2004. Completed suicide after a suicide attempt: a 37-year follow-up study. Am. J. Psychiatry 161, 562–563.

Tidemalm, D., Beckman, K., Dahlin, M., Vaez, M., Lichtenstein, P., Långström, N., Runeson, B., 2015. Age-specific suicide mortality following non-fatal self-harm: national cohort study in Sweden. Psychol. Med. 45, 1699–1707.

Vuagnat, A., Jollant, F., Abbar, M., Hawton, K., Quantin, C., 2019. Recurrence and mortality 1 year after hospital admission for non-fatal self-harm: a nationwide population-based study. Epidemiol. Psychiatr. Sci. 1–10.

Whiteford, H.A., Degenhardt, L., Rehm, J., Baxter, A.J., Ferrari, A.J., Erskine, H.E., Charlson, F.J., Norman, R.E., Flaxman, A.D., Johns, N., Burstein, R., Murray, C.J., Vos, T., 2013. Global burden of disease attributable to mental and substance use disorders: findings from the Global Burden of Disease Study 2010. Lancet 382, 1575–1586.

Witt, K.G., Hetrick, S.E., Rajaram, G., Hazell, P., Taylor Salisbury, T.L., Townsend, E., Hawton, K., 2021. Interventions for self-harm in children and adolescents. Cochrane Database Syst. Rev. 3, CD013667.

World Health Organization, 2019. Suicide in the world: Global Health Estimates. World Health Organization, Geneva, p. 32.

Zalsman, G., Hawton, K., Wasserman, D., van Heeringen, K., Arensman, E., Sarchiapone, M., Carli, V., Höschl, C., Barzilay, R., Balazs, J., Purebl, G., Kahn, J.P., Sáiz, P.A., Lipsicas, C.B., Bobes, J., Cozman, D., Hegerl, U., Zohar, J., 2016. Suicide prevention strategies revisited: 10-year systematic review. Lancet Psychiatry 3, 646–659.
significant follow-up period of 3 years, confirms the high rates of repeated self-harm and mortality in adolescents and young adults hospitalized for self-harm. One fifth exhibited repeated self-harming behaviors, usually in the short-term, and one in two hundred died at a young age, from suicide but also other causes. Research on both the mechanisms of self-harm in youths and individual and collective intervention strategies should be a national priority.

### CRediT authorship contribution statement

**Karine Goueslard:** Conceptualization, Formal analysis, Writing – original draft, Writing – review & editing. **Catherine Quantin:** Conceptualization, Funding acquisition, Supervision, Writing – review & editing. **Fabrice Jollant:** Conceptualization, Funding acquisition, Supervision, Writing – original draft, Writing – review & editing.

### Declaration of competing interest

All authors declare no conflict of interest.

This study was funded by a grant from the French Ministry of Health, Department of statistics (*Direction de la recherche, des études, de l'évaluation et des statistiques, DREES*) in 2018 to CQ and FJ.

### Acknowledgment

The authors want to thank Mrs Gwenaelle Periard for her help with manuscript editing and Mrs Suzanne Rankin for language editing.

### Supplementary materials

Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.psychres.2024.115807.

### References

Ammerman, B.A., Jacobucci, R., Kleiman, E.M., Uyeji, L.L., McCloskey, M.S., 2018. The relationship between nonsuicidal self-injury age of onset and severity of self-harm. Suicide Life Threat. Behav. 48, 31–37.

Asberg, M., Traskman, L., Thoren, P., 1976. 5-HIAA in the cerebrospinal fluid. A biochemical suicide predictor? Arch. Gen. Psychiatry 33, 1193–1197.

Bezin, J., Duong, M., Lassalle, R., Droz, G., Pariente, A., Blin, P., Moore, N., 2017. The national healthcare system claims databases in France, SNIIRAM and EGB: powerful tools for pharmacoepidemiology. Pharmacoepidemiol. Drug Saf. 26, 954–962.

Borschmann, R., Becker, D., Coffey, C., Spry, E., Moreno-Betancur, M., Moran, P., Patton, G.C., 2017. 20-year outcomes in adolescents who self-harm: a population-based cohort study. Lancet Child Adolesc. Health 1, 195–202.

Brager-Larsen, A., Zeiner, P., Klungsøyr, O., Mehlum, L., 2022. Is age of self-harm onset associated with increased frequency of non-suicidal self-injury and suicide attempts in adolescent outpatients. BMC Psychiatry 22, 58.

Carroll, R., Metcalfe, C., Gunnell, D., 2014. Hospital presenting self-harm and risk of fatal and non-fatal repetition: systematic review and meta-analysis. PLoS. One 9, e89944.

Favril, L., Yu, R., Uyar, A., Sharpe, M., Fazel, S., 2022. Risk factors for suicide in adults: systematic review and meta-analysis of psychological autopsy studies. Evid. Based. Ment. Health 25, 148–155.

Finkelstein, Y., Macdonald, E.M., Hollands, S., Hutson, J.R., Sivilotti, M.L., Mamdani, M. M., Koren, G., Juurlink, D.N., Canadian Drug Safety and Effectiveness Research Network, C.D.S.E.R.N., 2015. Long-term outcomes following self-poisoning in adolescents: a population-based cohort study. Lancet Psychiatry 2, 532–539.

GBD, A.M.C., 2021. Global, regional, and national mortality among young people aged 10-24 years, 1950-2019: a systematic analysis for the Global Burden of Disease Study 2019. Lancet 398, 1593–1618.

Gillies, D., Christou, M.A., Dixon, A.C., Featherston, O.J., Rapti, I., Garcia-Anguita, A., Villasenor-Keever, M., Reebye, P., Christou, E., Al Kabir, N., Christou, P.A., 2018. Prevalence and characteristics of self-harm in adolescents: meta-analyses of community-based studies 1990-2015. J. Am. Acad. Child Adolesc. Psychiatry 57, 733–741.

Goueslard, K., Jollant, F., Cottenet, J., Bechraoui-Quantin, S., Rozenberg, P., Simon, E., Quantin, C., 2023. Hospitalization for non-lethal self-harm and premature mortality in the three years following adolescent pregnancy: population-based nationwide cohort study. BJOG.

Hawton, K., Bale, L., Brand, F., Townsend, E., Ness, J., Waters, K., Clements, C., Kapur, N., Geulayov, G., 2020. Mortality in children and adolescents following

presentation to hospital after non-fatal self-harm in the Multicentre Study of Self-harm: a prospective observational cohort study. Lancet Child Adolesc. Health 4, 111–120.

Hawton, K., Bergen, H., Kapur, N., Cooper, J., Steeg, S., Ness, J., Waters, K., 2012a. Repetition of self-harm and suicide following self-harm in children and adolescents: findings from the multicentre study of self-harm in England. J. Child Psychol. Psychiatry 53, 1212–1219.

Hawton, K., Bergen, H., Waters, K., Ness, J., Cooper, J., Steeg, S., Kapur, N., 2012b. Epidemiology and nature of self-harm in children and adolescents: findings from the multicentre study of self-harm in England. Eur. Child Adolesc. Psychiatry 21, 369–377.

Hawton, K., Saunders, K.E., O'Connor, R.C., 2012c. Self-harm and suicide in adolescents. Lancet 379, 2373–2382.

Herbert, A., Gilbert, R., Cottrell, D., Li, L., 2017. Causes of death up to 10 years after admissions to hospitals for self-inflicted, drug-related or alcohol-related, or violent injury during adolescence: a retrospective, nationwide, cohort study. Lancet 390, 577–587.

Jollant, F., Goueslard, K., Hawton, K., Quantin, C., 2022. Self-harm, somatic disorders and mortality in the 3 years following a hospitalisation in psychiatry in adolescents and young adults. Evid. Based Ment. Health ebmental-2021.

Jollant, F., Hawton, K., Vaiva, G., Chan-Chee, C., du Roscoat, E., Leon, C., 2020. Non-presentation at hospital following a suicide attempt: a national survey. Psychol. Med. 1–8.

Lübbert, M., Bahlmann, L., Sobanski, T., Schulz, A., Kastner, U.W., Walter, M., Jollant, F., Wagner, G., 2022. Investigating the clinical profile of suicide attempters who used a violent suicidal means. J. Clin. Med. 11, 7170.

Madge, N., Hawton, K., McMahon, E.M., Corcoran, P., De Leo, D., de Wilde, E.J., Fekete, S., van Heeringen, K., Ystgaard, M., Arensman, E., 2011. Psychological characteristics, stressful life events and deliberate self-harm: findings from the Child & Adolescent Self-harm in Europe (CASE) Study. Eur. Child Adolesc. Psychiatry 20, 499–508.

Miranda-Mendizabal, A., Castellví, P., Parés-Badell, O., Alayo, I., Almenara, J., Alonso, I., Blasco, M.J., Cebrià, A., Gabilondo, A., Gili, M., Lagares, C., Piqueras, J.A., Rodríguez-Jiménez, T., Rodríguez-Marín, J., Roca, M., Soto-Sanz, V., Vilagut, G., Alonso, J., 2019. Gender differences in suicidal behavior in adolescents and young adults: systematic review and meta-analysis of longitudinal studies. Int. J. Public Health 64, 265–283.

Moran, P., Coffey, C., Romaniuk, H., Olsson, C., Borschmann, R., Carlin, J.B., Patton, G. C., 2012. The natural history of self-harm from adolescence to young adulthood: a population-based cohort study. Lancet 379, 236–243.

Morgan, C., Webb, R.T., Carr, M.J., Kontopantelis, E., Green, J., Chew-Graham, C.A., Kapur, N., Ashcroft, D.M., 2017. Incidence, clinical management, and mortality risk following self harm among children and adolescents: cohort study in primary care. BMJ 359, j4351.

Muehlenkamp, J.J., Xhunga, N., Brausch, A.M., 2019. Self-injury age of onset: a risk factor for NSSI severity and suicidal behavior. Arch. Suicide Res. 23, 551–563.

O'Connor, R.C., Rasmussen, S., Miles, J., Hawton, K., 2009. Self-harm in adolescents: self-report survey in schools in Scotland. Br. J. Psychiatry 194, 68–72.

Olsson, M., Wall, M., Wang, S., Crystal, S., Bridge, J.A., Liu, S.M., Blanco, C., 2018. Suicide after deliberate self-harm in adolescents and young adults. Pediatrics.

Perrain, R., Dardennes, R., Jollant, F., 2020. Risky decision-making in suicide attempters, and the choice of a violent suicidal means: an updated meta-analysis. J. Affect. Disord. 280, 241–249.

Ribeiro, J.D., Franklin, J.C., Fox, K.R., Bentley, K.H., Kleiman, E.M., Chang, B.P., Nock, M.K., 2016. Self-injurious thoughts and behaviors as risk factors for future suicide ideation, attempts, and death: a meta-analysis of longitudinal studies. Psychol. Med. 46, 225–236.

Suominen, K., Isometsä, E., Suokas, J., Haukka, J., Achte, K., Lonnqvist, J., 2004. Completed suicide after a suicide attempt: a 37-year follow-up study. Am. J. Psychiatry 161, 562–563.

Tidemalm, D., Beckman, K., Dahlin, M., Vaez, M., Lichtenstein, P., Långström, N., Runeson, B., 2015. Age-specific suicide mortality following non-fatal self-harm: national cohort study in Sweden. Psychol. Med. 45, 1699–1707.

Vuagnat, A., Jollant, F., Abbar, M., Hawton, K., Quantin, C., 2019. Recurrence and mortality 1 year after hospital admission for non-fatal self-harm: a nationwide population-based study. Epidemiol. Psychiatr. Sci. 1–10.

Whiteford, H.A., Degenhardt, L., Rehm, J., Baxter, A.J., Ferrari, A.J., Erskine, H.E., Charlson, F.J., Norman, R.E., Flaxman, A.D., Johns, N., Burstein, R., Murray, C.J., Vos, T., 2013. Global burden of disease attributable to mental and substance use disorders: findings from the Global Burden of Disease Study 2010. Lancet 382, 1575–1586.

Witt, K.G., Hetrick, S.E., Rajaram, G., Hazell, P., Taylor Salisbury, T.L., Townsend, E., Hawton, K., 2021. Interventions for self-harm in children and adolescents. Cochrane Database Syst. Rev. 3, CD013667.

World Health Organization, 2019. Suicide in the world: Global Health Estimates. World Health Organization, Geneva, p. 32.

Zalsman, G., Hawton, K., Wasserman, D., van Heeringen, K., Arensman, E., Sarchiapone, M., Carli, V., Höschl, C., Barzilay, R., Balazs, J., Purebl, G., Kahn, J.P., Sáiz, P.A., Lipsicas, C.B., Bobes, J., Cozman, D., Hegerl, U., Zohar, J., 2016. Suicide prevention strategies revisited: 10-year systematic review. Lancet Psychiatry 3, 646–659.