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The effects of interventions preventing self-harm and suicide in children and adolescents : an overview of systematic reviews

Self-harm and suicide in children and adolescents are of Background: serious consequence and increase during the adolescent years. Consequently, there is need for interventions that prevent such behaviour. The objective of this paper: to evaluate the effects of interventions preventing self-harm and suicide in children and adolescents in an overview of systematic reviews. We conducted a review of systematic reviews (OoO). We Methods: included reviews evaluating any preventive or therapeutic intervention. The quality of the included reviews was assessed independently, and data was extracted by two reviewers. We report the review findings descriptively. The certainty of the evidence was assessed using Grading of Recommendations Assessment, Development and Evaluation (GRADE). Moderate certainty evidence suggests that school-based Results: interventions prevent suicidal ideation and attempts short term, and possibly with long term effects on suicide attempts. The effects of community-based interventions following suicide clusters and local suicide plans are uncertain, as are the benefits and harms of screening young people for suicide risk. The effects of most interventions targeting children and adolescents with known self-harm are uncertain. However, low certainty evidence suggests that dialectical behavioural therapy and developmental group therapy are equally as effective on repetition of self-harm as enhanced treatment as usual. Research on several recommended practices, such as local Conclusions: suicide plans, prevention of suicide clusters and approaches to risk assessment, is lacking. When implemented, these interventions should be closely evaluated. There also is need for more research on treatment for repeated self-harm, including long term follow-up, and in general: possible harmful effects. Policy makers and health providers should consider evidence from population-based studies and adults in preventing self-harm and suicide in children and adolescents. Also, approaches showing promise in treatment of conditions associated with self-harm and/or suicidality, such as 1 1 2

Introduction Self-harm involves intentional self-poisoning or self-injury, irrespective of type of motive or the extent of suicidal intent 1,2 . It is often a coping mechanism used to solve a difficult situation and can serve several functions. Affect regulation, managing painful unpleasant emotional states including making emotional pain physical and blocking bad memories, is commonly reported 3 . Self-harm can also serve interpersonal functions, such as seeking help from someone or communicating the extent of pain 3 . In addition, people who self-harm sometimes report self-punishment as a motivation 3 . Completed suicide is defined as the act of intentionally ending one's own life 4 . Self-harm and suicide result from underlying factors such as other mental health problems, exposure to traumatic events or other difficult circumstances in the young person's environment. Exposure to family and/or friends self-harm and suicide may contribute to self-harm and suicide in adolescents, a phenomenon referred to as "social contagion" 5 .
Self-harm is prevalent among adolescents 6 . Due to few studies on self-harm in individuals younger than 12 years, it is hard to estimate the prevalence of self-harm in children in the community. However, presentations to hospital after self-harm are rare in this age-group 5 . Across international studies, 18% of adolescents between the ages of 12 and 18 report a history of one or several episodes of intentional self-harm. Prevalence is highest amongst adolescent girls, but it is also a problem amongst boys 7 . Some studies indicate that the gender differences are smaller than previously assumed, and that boys often inflict self-injury in other ways than girls; while girls often cut themselves, boys more often hit themselves 8 . Self-harm may be a temporary or more long-lasting in nature 7 , and one episode of self-harm is a strong predictor of repetition of this behaviour 9,10 . When selfharm is repeated, the person often advances to a combination of different methods, increasing the medical severity 11 . Suicide is on the other hand rare before the age of 15 but increases in prevalence through adolescence 6 . In most parts of the world, male adolescents are more likely to commit suicide than female adolescents 12 . It is the most common cause of death in female adolescents, and the third most common cause of death in male adolescents (after road-traffic accidence and violence) 6 . As such, that there is clearly a need for effective prevention of self-harm and suicide in children and adolescents. Several reviews of interventions for preventing self-harm and suicide exist. However, many are of variable quality, or are outdated [13][14][15][16][17][18] . As is the case for many health conditions, there is a large overlap in topics covered by the reviews, making it difficult for professionals to sort out the best available evidence in making informed decisions 19 . Consequently, we wanted to provide an up-to-date overview of the best quality summarized evidence of effects of interventions aimed at preventing self-harm and suicide, supporting informed decision-making.

Objective
The objective of this review is to summarize the effects of interventions for preventing self-harm and suicide in children and adolescents.

Methods
This review was registered with the international prospective register of systematic reviews (PROSPERO; CRD42019117942) on 08 February 2019.

Inclusion and exclusion criteria
We included systematic reviews published in 2012 and later (last date searched August 2018), with publications in English, Norwegian, Danish or Swedish, and fulfilling the DAREcriteria 20 . The inclusion criteria (PICO) is presented in Box 1.

Box 1.
Population: Children and adolescents under 18 with or without an identified risk of developing problems involving self-harm and/or suicide, or those who have already developed these problems.
Intervention: Any intervention aimed at preventing or reducing self-harm and suicide, including psychological therapy, pharmaceutical interventions, psychosocial interventions, physical activity or nutrition.

Control:
Other relevant interventions, treatment as usual (TAU) or wait list.
Outcome: All outcomes evaluated in children and youth, including (but not restricted to) self-harm, completed suicide, other health outcomes, quality of life, function, use of health care, attitudes and unwanted effects of interventions.
We excluded systematic reviews that did not meet the criteria for the above-mentioned PICO: • Children and adolescents with other main-diagnosis, e.g. children admitted to hospitals because of somatic illness at the same time as experiencing depressive symptoms.
• Interventions preventing other behaviours with no direct association with mental health, e.g. interventions targeting smoking cessation.
• Pharmaceutical interventions compared to placebo. This review was conducted to inform decision-making in Norway, and for this purpose only direct comparisons between pharmaceutical treatments were judged to be relevant.

Literature search
The literature search for this review was completed in August 2018 and is largely based on IN SUM: a database of systematic reviews on effects of child mental health and welfare interventions 21  The present review of systematic reviews was developed following the principles of the Cochrane handbook 23 . Two researchers independently reviewed all publications indexed in IN SUM (two of the athors: AD or ISM, and/or a research colleague KTH). We also hand-searched for relevant systematic reviews, in the following databases and organisations: • The Norwegian Institute of Public Health • The Swedish agency for health technology assessment and assessment of social services(SBU) • The Norwegian Directorate of Health • The Danish Health Authority • The National Institute for Health and Care Excellence (NICE) All publications judged to meet the inclusion criteria were retrieved in full text. Two researchers (ISM, AA) independently screened and assessed all full text publications for potential inclusion.
In cases of disagreement, we consulted a third person.

Assessment of overlap between reviews and methodological quality
We sorted all included reviews by population and which interventions were compared (the PICOs). In cases were more than one review addressed the same treatment comparison for the same population, we included the review with the newest search (and completeness of this search by considering the included studies) and the best quality. In considering overlap, the first author (ISM) extracted this information from the reviews and the second author (AA) double-checked this information. Further, we assessed the quality of the included reviews based on a checklist for systematic reviews (AMSTAR: A MeaSurement Tool to Assess systematic Reviews) 24 . Two people (ISM, IB) considered each publication independently and decided on the methodological quality through discussions until consensus.
The final decision on which reviews to include was done through agreement between two of the authors (ISM and AA). Table 1 contains documentation on characteristics of the included reviews, including methodological quality.
Data extraction and analyses ISM extracted data from the systematic reviews and AA checked its accuracy. As this was an overview of systematic reviews, we extracted information as it was reported in the systematic reviews, including any supplementary tables or appendixes. We did not retrieve primary studies to provide additional information about interventions or results.
From the systematic reviews, we extracted information about the primary studies populations, characteristics of the interventions and comparison groups, duration of the interventions, follow-up periods, outcome measures and pooled effect estimates for each outcome. In cases were the effect estimates were not pooled in a meta-analysis, we reported the results of each individual study for each outcome.
We did not attempt any reanalysis, but present results as reported in the systematic reviews. For reviews also including studies on adult populations, we only extracted information from studies of children and adolescents. When reported, the effect estimates were presented with relevant measures of uncertainty.
Assessing the certainty of evidence and reporting of results We assessed our confidence in the evidence of effect for each outcomes using the GRADE methodology (the Grading of Recommendations Assessment, Development and Evaluation) 25 . If the systematic review authors had already completed a GRADE assessment, we reviewed this. We describe our confidence in the effect estimates as high, moderate, low or very low for each outcome.

Results
Results of the literature search All 1259 references in the INSUM database was reviewed for potential relevance (see Figure 1). Additionally, we also identified 12 records through hand-searches. We excluded 1242 of these based on title or summary, mainly because they focused on other diagnosis or problem-areas than self-harm and/or suicide. Overall, 29 full texts were retrieved, 12 were excluded because they did not fulfil the inclusion criteria. Out of 18 potentially included reviews, 9 were excluded because of overlap (see Table 2 for excluded studies). Figure 1 describes the search-process and the number of articles excluded in each step. Eight systematic reviews 1,13,14,26-30 , including summary of new evidence of two of them 31,32 , were consequently included in the analysis. One review was identified after we had completed the analysis 33 and is therefore not included in the present review of systematic reviews.
Although the initial cut-off for age in our population was 18, two of the reviews included studies with young people up to 24 26,27 . These were included because the upper age limit used to define adolescence in research on self-harm and suicides varies between 18 and 25 5 .

Description of interventions
The reviews included a broad range of interventions. Most of the studies included adolescent populations in the age-range 12 to 18, with some exceptions of samples including younger children or young adults up to the age of 24. Preventive interventions were either primary prevention strategies for mixed population based samples (suicide awareness campaigns and other school-based prevention programs, screening for suicide

All types if interventions
Interventions for existing self-harm: therapeutic assessment versus treatment as usual (TAU) Population: Adolescents, 12-18-year olds, referred for a psychosocial assessment following an episode of self-injury or self-poisoning, irrespective of intent Intervention: Standard psychosocial history and suicide assessment, a review of this information, identification of target problems, considering ways to change them and motivations to do so, and alternative problem-solving strategies Control: Treatment as usual comprised of standard psychosocial history and suicide risk assessment Length

Date of search
The authors' defined study population Interventions for existing self-harm: developmental group therapy versus TAU Population: Adolescents, 12 to 17-year olds, referred to child and adolescent services following an episode of intentional self-injury or self-poisoning, irrespective of intent Intervention: Manualised developmental group psychotherapy involving elements of cognitive behavioural therapy, social skills training, interpersonal psychotherapy, dialectical behavioural therapy, and group psychotherapy with or without addition to treatment as usual Control: Treatment as usual (i.e. individual counselling, family individual-based interventions such as counselling, family sessions, pharmaceutical treatment) Length of intervention: Acute treatment phase weekly sessions over 6 weeks, followed by weekly or biweekly booster sessions as long as required Follow-up period: 6 and 12 months Interventions for existing self-harm: other psychotherapeutic approaches (no primary studies identified) Interventions for existing self-harm: nutrition No primary studies identified Interventions for existing self-harm: pharmacological treatment No primary studies identified Interventions for existing self-harm: compliance enhancement versus TAU Population: Children and adolescents, 10 to 19-year olds, admitted to the emergency department of a general hospital following an episode of self-injury irrespective of intent, and/or increased risk for suicidality Intervention: a single, one-hour session that reviewed expectations for outpatient treatment as well as addressing factors likely to impede attendance and treatment misconceptions and encouraged both the adolescent and parent to make verbal contract and to attend all treatment sessions. Follow-up phone-calls 1, 2, 4 and 8 weeks after disposition. Control: TAU Length of intervention: 8 weeks Follow-up period: 3 months Interventions for existing self-harm: home-based family intervention versus TAU Population: Adolescents aged 16 or younger referred to child and adolescent mental health services following an episode of selfpoisoning irrespective of intent Intervention: manualised home-based family therapy intervention involving one assessment session and 4 home visits in addition to treatment as usual Control: Treatment as usual Length of treatment: Not stated Follow-up period: 6 months Interventions for existing self-harm: emergency cards plus TAU versus TAU Population: adolescents in the ages of 12 to 16 admitted to hospital after an episode of self-injury or self-poisoning Intervention: emergency green card in addition to usual care. The green card acted as a passport to re-admission into a paediatric ward at the local hospital Control: standard follow-up including treatment from a clinic or child psychiatry department as required Length of intervention: 12 months Follow-up period: 12 months Interventions for existing self-harm: postcards versus TAU Population: Adolescents and young adults between the ages of 15 to 24 with a history of suicidal threats, ideation, attempts and/or selfinjury who did not meet entry criteria for service because they either were not well enough or were receiving treatment elsewhere Intervention: Postcards mailed out monthly over 12 months expressing interest for that person`s well-being, remining him or her about previously identified sources of help and describing one of six rotating self-help strategies (e.g. physical activity, books, Web-sites) Control: Treatment as usual Length of intervention: 12 months Follow-up period: Post-intervention   risk) or secondary preventions strategies (local approaches following suicide clusters, suicide prevention in residential custodial and detention settings, interventions to support children and adolescents bereaved or affected by a suspected suicide) 14,26,27 . The reviews also included psychosocial or psychological intervention in cases of existing self-harm (defined as a history of at least one episode of self-harm) (therapeutic assessment, mentalization based therapy, dialectic behaviour therapy, cognitive behaviour therapy, developmental group therapy, compliance enhancement, home-based family intervention, emergency green cards, digital interventions for self-management of suicidal ideation and self-harm, postcards) 13,27,28,31 .

Summary of findings
The effects of interventions are presented by type population (young people with or without an identified risk, or with existing self-harm, e.g. a history of at least one episode of self-harm) and by treatment comparison. Our assessment of certainty on the evidence corresponds to GRADE-tables in Table 3-Table 18.
For comparisons with many outcomes, we report the main outcomes in the present results section. See GRADE- Table 3-Table 18 for the remaining outcomes.
For the following interventions (versus treatment as usual (TAU) or alternative interventions), the review authors also searched for research on effects, but did not identify studies on children and adolescents under the age of 18 were not identified. These are primary and secondary preventive interventions (reducing access to means, local suicide plans, local media reporting of suicides in newspapers, Internet or other digital channels, suicide prevention in residential custodial and detention settings) 26 and interventions for existing self-harm (assessment in children and adolescents at the emergency department, psychoeducation, pharmacological treatment or a combination of pharmacological treatment and psychotherapy, nutrition, other psychotherapeutic approaches such as problem-solving therapy, Table 2. Systematic reviews excluded after full text assessment.       psychodynamic therapy, multi-systemic therapy, supportive therapy, or other psychosocial approaches such as counselling, self-management, respite care, assertive outreach) 1,28-32 .

School-based suicide prevention programs versus TAU, alternative interventions, wait list or no intervention.
The evidence includes 13 studies with <337 221 children and adolescents aged 10 to 23, as well as personnel in different local arenas working with young people 14,26 . In one of the studies, the participants (n=320 500) were habitants in a county in which county-based prevention programs were implemented. These participants included school students and personnel in schools and other local arenas. School-based prevention programs probably reduce suicidal ideation (RR 0.67, 95% KI 0.48 to 0.93, moderate certainty⊕⊕⊕⊝) and suicide attempts (RR 0.53, 95% KI 0.36 to 0.80, moderate certainty⊕⊕⊕⊝) at three to 12 months. Regarding suicide attempts, three studies conclude accordingly at six-and 12-month follow-up period. This effect possibly holds at ≥twoand 15-year followup (low certainty⊕⊕⊝⊝). Further, school-based interventions possibly reduce the rate of completed suicides at three-year follow-up (low certainty⊕⊕⊝⊝). Effects on help-seeking and possible unwanted effects are unclear since the evidence for these outcomes is of very low certainty⊕⊝⊝⊝. See Table 3.

Primary prevention: local approaches following suicide clusters versus historical control.
The evidence includes three studies with children and adolescents between the ages of 10 and 24 26 . Follow-up period was up to four years. The evidence of effects of local approaches following suicide clusters is of very low certainty⊕⊝⊝⊝. See Table 4.

Secondary prevention: interventions to support children and adolescents bereaved or affected by a suspected suicide compared to TAU or historical control.
The evidence includes two studies 26 . The evidence of effects of interventions to support children and adolescents bereaved or affected by a suspected suicide is of very low certainty⊕⊝⊝⊝. See Table 5.

Primary prevention: screening for suicide risk versus no screening.
The evidence is based on one review 27 . The review authors did not identify studies evaluating beneficial effects of screening as a preventive strategy in children or adolescents. They did however identify two studies evaluating harms associated with screening for psychological distress and a history of deliberate self-harm and suicidal ideation in primary care settings. The studies comprised of 2650 adolescents between 13 and 19 years old, and the evidence is of very low certainty⊕⊝⊝⊝. See Table 6.
Interventions for children and adolescents with existing self-harm.
Interventions for existing self-harm: therapeutic assessment versus TAU. The evidence includes one study with 70 adolescents, 12 to 18-year olds, referred for a psychosocial assessment following an episode of self-injury or self-poisoning, irrespective of intent 28 . Length of intervention was one hour and 40 minutes. Follow up was 12 and 24 months. The evidence of effects of therapeutic assessment is of very low certainty⊕⊝⊝⊝. See Table 7.

Interventions for existing self-harm: mentalization based therapy (MBT-A) versus TAU.
The evidence includes one study with 80 adolescents, 12 to 17-year olds, diagnosed with depression  presenting to emergency departments or community psychiatric services following an episode of self-injury or self-poisoning, irrespective of whether suicidal intent was present 28 . Length of treatment was 12 months, and follow-up period was also 12 months. The evidence of effects of therapeutic assessment is of very low certainty⊕⊝⊝⊝. See Table 8.

Interventions for existing self-harm: dialectical behaviour therapy (DBT-A) versus TAU or enhanced TAU.
The evidence includes two studies with 106 adolescents between the age of 12 and 19 years old with a history of multiple episodes self-harm 28,31 .
Length of treatment was 19 weeks. Follow-up period was 16 weeks and six months. Based on the available evidence DBT-A has little or no effect on repetition or frequency of self-harm (OR 0.72, 95% KI 0.12 to 4.40, low certainty⊕⊕⊝⊝). DBT-A may have a moderate effect on reduction of suicidal ideation (SMD -0.62, 95% KI -1.07 to -0.16, low certainty⊕⊕⊝⊝). The certainty of the evidence for other outcomes is very low⊕⊝⊝⊝. See Table 9. contains one study with 39 adolescents between the age of 12 and 17 presenting to a paediatric general or psychiatric facility following self-injury in which an intent to die was indicated 28 . Length of treatment was six months. Follow-up period was three, six and 12 months. The certainty of the evidence for CBT versus non-directive psychotherapy is very low⊕⊝⊝⊝. See Table 10.

Interventions for existing self-harm: developmental group therapy versus TAU.
The evidence contains three studies of 487 adolescents, 12 to 17-year olds, referred to child and adolescent services following an episode of intentional self-injury or self-poisoning, irrespective of intent 28 . Acute treatment phase was six weekly sessions, followed by weekly or biweekly booster sessions for as long as required. Follow-up period was between six and 12 months. Based on the available evidence, the effects of developmental group therapy are uncertain on the following outcomes: repetition of self-harm (six months: OR The evidence for all the outcomes is of low certainty⊕⊕⊝⊝. See Table 11.

Interventions for existing self-harm: compliance enhancement versus TAU.
The evidence contains one study of 76 adolescents, 12 to 19-year olds, admitted to the emergency department of a general hospital following an episode of selfinjury, irrespective of intent, and/or with an increased risk for suicidality 28 . Length of treatment was eight weeks. Follow-up period was three months. The evidence of effects of compliance enhancement is of very low certainty⊕⊝⊝⊝. See Table 12.

Interventions for existing self-harm: home based family intervention versus TAU.
The evidence contains one study in a sample of adolescents aged 16 years or younger referred to child and adolescent mental health services following an episode of self-poisoning irrespective of intent 28 . The intervention was a manualised home-based family therapy intervention. Follow-up period was six months. The evidence of effects of home-based family intervention is of very low certainty⊕⊝⊝⊝. See Table 13.

Interventions for existing self-harm: emergency green cards plus TAU versus TAU.
The evidence contains one study with 105 adolescents between the ages of 12 and 16 who were admitted to hospital following an episode of self-injury or selfpoisoning 28 . The intervention was emergency green cards in addition to usual care. The green card acted as a passport to re-admission into a paediatric ward at the local hospital. Length of treatment was 12 months. Follow-up period was 12 months. The evidence of effects of emergency green cards is of very low certainty⊕⊝⊝⊝. See Table 14.

Interventions for existing self-harm: digital interventions for self-management of suicidal ideation and self-harm versus
psychoeducation or historical control. The evidence contains three studies with 184 adolescents reporting suicidal thoughts and/or receiving treatment for depression 13 . The interventions spanned from two to 12 weeks and follow-up was post treatment. The evidence of effects of digital interventions for selfmanagement is of very low certainty⊕⊝⊝⊝. See Table 15.

Interventions for existing self-harm: postcards versus TAU.
The evidence is based on two systematic reviews 27,31 . One of the reviews 31 included one study with 2300 adolescents and young adults over the age of 12 previously admitted to a specialist poisons hospital after self-poisoning. The other review 27 included one study of 165 adolescents and young adults of 15 to 24 years old with a history of suicidal threats, ideation, attempts and/or self-injury who did not meet entry criteria for service because they either were not unwell enough Table 14. GRADE-assessment: Interventions for existing self-harm: emergency green cards versus treatment as usual (TAU).
Population: Adolescents aged 16 years or younger who were admitted to hospital following an episode of self-injury or self-poisoning to re-admit themselves to a paediatric ward in the local hospital on demand if they felt suicidal Intervention: Emergency green cards Control: TAU (standard follow-up including treatment from a clinic or child psychiatry department as required)

Downgraded by 1 level due to imprecision (few participants/incidences).
or were receiving treatment elsewhere. Follow-up was post study. The evidence of effects of postcards is of very low certainty⊕⊝⊝⊝. See Table 16.

Strengths and limitations
The major contribution of this review is to provide children, adolescents and their families, clinicians and researchers with an overview of research regarding the effects of interventions for young people to prevent suicide and (re)occurrence of selfharm. For this purpose, we have used systematic and transparent criteria [23][24][25] . The results of our review should be supplemented with other relevant research and integrated with clinical expertise as well as the child's or adolescent's and their caregiver's values and preferences 34,35 .
A limitation of overviews of reviews, and consequently of this present report, is that the analyses are based on secondary reporting and the interpretation of the review authors. Thus, the primary studies may have provided more information than what is reported in the reviews we included. Nevertheless, the present report provides insight into the certainty of the evidence of effects of treatments and other interventions that have been evaluated. This report also identifies important research gaps for interventions where no studies have been conducted. Acknowledging that the effects of these interventions in reducing self-harm and suicide are uncertain can prompt new research efforts important for children and adolescents.
It is also worth noting that the present report only included reviews of studies where the population was children and young people with existing self-harm or preventive strategies for children and adolescents with or without an identified risk of selfharm and suicide. As mentioned in the introduction, self-harm  3. Downgraded by 2 levels due to study design (2 out of 3 studies were observational).
and suicide are outcomes associated with other underlying difficulties. Therefore, evidence from studies including young people with problem such as other mental health issues typically associated with self-harm may provide important direction in decision-making when faced with self-harm and suicide. However, in the existing research-base on e.g. psychosis, depression and anxiety, self-harm and suicide are rarely investigated as outcomes [36][37][38] . According to the existing low certainty evidence, combination treatment for depression (pharmacological treatment plus psychotherapy) may lead to a reduced risk for suicide 37 .

Summary of findings: preventive interventions
Based on the available research, there is moderate certainty evidence that school-based interventions can prevent suicidal ideation and suicide attempts short term, and low certainty evidence that they can prevent suicide attempts long term.
The certainty of the evidence for the effects of screening children and young people for symptoms of depression and a history of self-harm or suicidal ideation in the general population is very low, and the benefits and harms of such interventions are therefore unknown.
Local suicide plans are a recommended strategy in some countries 26,39 . However, the effects of such plans on preventing self-harm and suicide in children and young people is yet to be evaluated in research.
We identified no studies evaluating the effects of reducing access to means from children and young people specifically. However, studies on the general population, including populations with adults, suggests that this may be an effective strategy 26 .
Furthermore, there is a need for more research on how media reporting of suicides affects suicide rates in children and young people. However, studies at a population level suggests that certain forms of media reporting are associated with an increase in suicides 26 . Guidelines on how to report on suicides is one suggested strategy to address the harms of such reporting 26 .
The certainty of evidence for community-based interventions following suicide clusters is very low. The best strategies for addressing this phenomenon and later suicides following suicide clusters are therefore unknown. Even though research is scarce, some recommendations are agreed upon, e.g. provision of information to relevant agencies in the community and providing support for those directly affected or other vulnerable individuals 40 .
The reviews we identified also searched for studies targeting young people in residential custodial and detention settings. No studies evaluating interventions to prevent suicide in this high-risk population were identified. Therefore, effects uncertain.
Another high-risk group is young people bereaved or affected by a suicide in their family or other network. Two studies were identified addressing the effects of support-interventions in this population. However, the evidence is of very low certainty.

Summary of findings: interventions for existing self-harm
Based on the available evidence, it is uncertain which approach to risk assessment of young people after an episode of selfharm is most appropriate. Furthermore, the effects of psychoeducation, psychological therapy, psychosocial interventions, digital interventions for self-management and nutrition for treating young people with existing self-harm are uncertain. For most of these interventions no studies were found, or the certainty of the evidence was very low.
Two treatment comparisons evaluating psychological therapy provided evidence of their effectiveness (low certainty); dialectical behavioural therapy and developmental group therapy. Both treatments were compared to alternative psychological therapy, and there was little or no important difference in effect on repetition of self-harm compared to alternative follow up. However, of notice, there was substantially higher (although not statistically significant) repetition of self-harm amongst adolescents participating in group developmental therapy compared to those receiving individual therapy at six-month follow-up. At 12-month follow-up, there was little or no important effect on self-harm.
We found no studies on direct comparisons of pharmacological treatments or on the effects of combination therapy (pharmacological plus psychotherapy).
The evidence of effects of organization of services, such as home-based treatment and use of emergency green cards, is of very low certainty.
Suicide clusters, although rare, is of major concern. When faced with this phenomenon or in fear of potential social contagion following the suicide of an individual, communities are expected to act to prevent further social contagion and clustering.

Conclusions
Overall, evidence of moderate to low certainty suggests that school-based suicide prevention programs can prevent suicide and suicide attempts in young people.
The effects of community-based interventions following suicide clusters and local suicide plans are uncertain. Furthermore, it is not possible to make any conclusions about the benefits and harms of screening in young people or and without known risk of self-harm and suicide.
Evidence of low certainty suggests that dialectical behavioural therapy and developmental group therapy are equally as effective on repetition of self-harm as enhanced treatment as usual (individual and/or family psychotherapy). The effects of evidence for other interventions preventing self-harm and suicide is of very low certainty or remains to be evaluated. These includes approaches to risk assessment and how to best organize the care of young people with known self-harm or suicide risk.

Implications
Our review suggests that preventive strategies can reduce suicide risk. However, there is a lack of research on effects of recommended practices, such as local suicide plans and approaches to risk assessment. Screening for suicide risk as primary prevention may provide the opportunity of early detection, and if precise, offers the opportunity to provide young people at risk with appropriate treatment. However, screening is resource demanding, and beneficial and possible harmful effects are uncertain. When implemented, local suicide plans, approaches to risk assessment and screening programs should be closely evaluated.
It is recommended that communities prepare for situations with a risk for social contagion and suicide clusters. Research evaluating strategies to prevent clustering of suicides is scarce, and the studies we found used inappropriate designs to capture the potential beneficial or harmful effects of these interventions. We suggest that researchers design appropriate observational studies, allowing for enough observations pre-and postimplementation of preventive measures to inform policy.
There is great uncertainty associated with the effects of treatment strategies for young people with existing self-harm. More research is needed, including on younger children and long-term follow up.
Self-harm is a common reason for referral of adolescents in child and adolescent psychiatric services, and often accompanies other psychiatric symptoms presented in such settings. It follows that psychological or psychosocial approaches showing promise in treatment and prevention of conditions associated with self-harm and/or suicidality, such as depression and psychosis, should be considered in treatment of repeated selfharm. In general, when effects of interventions preventing self-harm and suicide in children and adolescents are uncertain due to lack of research or evidence of very low certainty, policy makers and health providers should consider evidence from population-based studies and adults.
It is crucial to be mindful that our own preventive actions or treatment efforts possibly could contribute to an increased risk for self-harm and suicide. Practice should be evaluated, and researchers should investigate harmful effects as well as beneficial effects of interventions.

Data availability
Underlying data All data underlying the results are available as part of the article and no additional source data are required.

Grant information
The present paper was funded by the Regional Centre for Child and Adolescent Mental Health, Eastern and Southern Norway (RBUP), the Regional Centre on violence, trauma and suicide prevention, Eastern Norway and the Norwegian Directorate of Health.
In addition, why the authors decided to include all publications in English, Norwegian, Danish or Swedish rather than simply including only studies in English language is a matter of debate and needs to be specified.
Moreover, the authors should immediately present and discuss, in the first lines of the Discussion section, their most relevant study findings. Conversely, they seem to focus with redundancy on the main aims/objectives of the paper which have been already presented elsewhere.
Although the authors reported that the present analyses are based on secondary reporting and the interpretation of the review authors as well as that the present report included only reviews of studies where the population was children and young people with existing self-harm, the most relevant limitations/shortcomings of the present study need to be more carefully described for the general readership.
Finally, what is the take-home message of this manuscript? While the authors stated that practice should be evaluated, and researchers should investigate harmful effects as well as beneficial effects of interventions, they failed, in my opinion, to provide some conclusive remarks about their findings. Here, some further details/information are needed.

Are the conclusions drawn adequately supported by the results presented in the review? Yes
No competing interests were disclosed.

Competing Interests:
Reviewer Expertise: Psychopathology and neurobiology of suicidal behavior and major affective disorders.
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.
Author Response 10 Feb 2020 , Regional Centre for Child and Adolescent Mental Health, Eastern and Ida Sund Morken Southern Norway (RBUP), Oslo, Norway First, as the authors, throughout the Introduction section, correctly stated that self-harm and 1) suicide are associated with relevant psychosocial impairment and result from underlying factors such as other mental health problems, exposure to traumatic events or other difficult circumstances in the young person's environment, they might even mention that the emotional turmoil in the case of suicide survivors of patients died by suicide may last a long time, and in some cases, may end with their own suicide. Thus, together with self-harm and suicide, it is fundamental to understand the bereavement process after the suicide of a significant other to provide a proper care, reduce stigma, and improve the outcomes. In addition, specific biological factors such as prolactin and thyroid hormone levels may be dysregulated and significantly associated with self-harm and suicide attempts and even involved in a complex compensatory mechanism to correct reduced central serotonin activity. The assumption that prolactin and thyroid hormones may be associated or even predict a suicide attempt is of great importance given the availability of such data in everyday clinical practice. Physicians of any kind as well as mental health professionals should be aware of the importance to insert as much information possible in the assessment of suicide and self-harm risk. Thus, given the above mentioned information, the authors could include throughout the manuscript, some published papers regarding the mentioned topics (PMID: 24082246; 31091772; 28843902; 22748186; 12866334).
Thank you for interesting suggestions. We have added information and some of the recommended citations in the introduction regarding the importance of bereavement as a risk factor in prevention of suicide, as well as in the section on "Effects of preventive interventions: summary of findings and implications", and about biological factors as possible risk factors in the introduction, as well as in "Effects of interventions for existing self-harm: summary of findings and implications".
In addition, why the authors decided to include all publications in English, Norwegian, Danish or 2) Swedish rather than simply including only studies in English language is a matter of debate and needs to be specified.
We Moreover, the authors should immediately present and discuss, in the first lines of the 3) Discussion section, their most relevant study findings. Conversely, they seem to focus with redundancy on the main aims/objectives of the paper which have been already presented elsewhere.
We agree, and are now more focused on our main findings in the beginning of the discussion.
Although the authors reported that the present analyses are based on secondary reporting and 4) the interpretation of the review authors as well as that the present report included only reviews of studies where the population was children and young people with existing self-harm, the most relevant limitations/shortcomings of the present study need to be more carefully described for the general readership.
We Finally, what is the take-home message of this manuscript? While the authors stated that 5) practice should be evaluated, and researchers should investigate harmful effects as well as beneficial effects of interventions, they failed, in my opinion, to provide some conclusive remarks about their findings. Here, some further details/information are needed.
Thank you, and we agree. We now have the take-home message as well as some further details/information in conclusive remarks about the finding in the conclusion.
No competing interests were disclosed. Competing Interests: summarised. Overall, the systematic review is very comprehensive but the discussion and summary could be more coherent and with a better flow. For instance, the authors can attempt to comment on the implications of TAU control group versus other active intervention control groups.

Are the rationale for, and objectives of, the Systematic Review clearly stated? Yes
Are sufficient details of the methods and analysis provided to allow replication by others? Partly

Is the statistical analysis and its interpretation appropriate? Not applicable
Are the conclusions drawn adequately supported by the results presented in the review? Yes No competing interests were disclosed.

Competing Interests:
Reviewer Expertise: Clinical psychology, mainly child and adolescent mental health, specifically self-harm or autism.

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.
Author Response 10 Feb 2020 , Regional Centre for Child and Adolescent Mental Health, Eastern and Ida Sund Morken Southern Norway (RBUP), Oslo, Norway The methodology provided is sufficient except it is unclear why only systematic reviews 1) published in 2012 or later are included.
· We thank reviewer 1 for pointing out that this was unclear. This cut-off is pragmatic but similar to that practiced by others, for example, the Cochrane Library (https://community.cochrane.org/editorial-and-publishing-policy-resource/cochrane-review-development/cochrane-r in considering that an older review is obsolete and no longer a reliable basis for evidence and in need for being updated. It takes time before a review is published, consequently a review may be published one to three years later than the search was done for primary studies. This has improved with time and new publication standards for reviews. Thus, a review published earlier than 2012 may not include primary studies published the last >10 years. A sentence to explain this has now been added to the manuscript.
It is also unclear what search terms were used for future replications.

Abstracts of Reviews of Effects (DARE) and Evidence Based Mental Health. A description of IN
I'm not sure if the authors are aware, but our group recently published a systematic review and meta-analysis of interventions to prevent suicide in young people -available here It may be worthwhile https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(18)30041-5/fulltext. including this in your review of reviews! No competing interests were disclosed.

Competing Interests:
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