Table 2.

Presentation of the definitions and measures of self-injury, nonsuicidal self-injury and bullying victimization across studies.

AUTHORS & YEAR/ STUDY ACRONYM	TIME PERIOD ASSESSED FOR SELF-INJURY	DELIBERATE SELF-HARD (DSH), SUICIDALITY & BULLYING VICTIMIZATION DEFINITIONS USED IN THE STUDIES	SELF-INJURY, SUICIADAL BEHAVIOR & DEPRESSIVE SYMPTOMS MEASURES	BULLYING VICTIMIZATION MEASURES
Brunner et al. 2014 / the SEYLE study	Lifetime prevalence	BSH: Intentional self- inflicted damage to the surface of an individual's body, which includes self-cutting, -burning, -biting, -hitting, and skin damage by other methods, regardless of suicidal intent.	DSH: 6-item questionnaire (SEYLE study): (a) Have you ever intentionally cut your wrist, arms, or other area(s) of your body, or stuck sharp objects into your skin such as needles, pins, staples (not including tattoos, ear piercing, needles used for drugs, or body piercing)? (b) Have you ever intentionally burned yourself with a cigarette, lighter, or match? (c) Have you ever intentionally carved words, pictures, designs, or other markings into your skin or scratched yourself to the extent that scarring or bleeding occurred? (d) Have you ever intentionally prevented wounds from healing, or bit yourself to the extent that it broke skin? (e) Have you ever intentionally banged your head or punched yourself causing a bruise? (f) Have you ever intentionally hurt yourself in any of the abovementioned ways so that it led to hospitalization or injury severe enough to require medical treatment? DS: BDI	Bullying victimization: a single yes/no question
Brunstein Klomek et al. 2016/ the SEYLE study	Lifetime prevalence	DSH: Intentional self-inflicted damage to the surface of an individual's body, which includes self-cutting, -burning, -biting, -hitting, and skin damage by other methods, regardless of suicidal intent.	DSH: 6-item questionnaire about intentional self- inflicted damage of the surface of an individual's body by self-cutting, -burning, -hitting, -biting, and skin damage by other methods. (SEYLE: deliberate self-harm inventory-WSII) DS: BDI	Physical/verbal/relational bullying victimization: Ten yes/no questions about the three different types of victimization (e.g., “others pushed, hit or kicked you”; “others called you names”, “others spread rumours about you” & their frequency (occasional/ repetitive)
Claes et al. 2015	Lifetime prevalence	NSSI: Deliberate and direct injury of one's own body tissue without suicidal intent, such as scratching, cutting, hitting, and burning oneself.	NSSI: The NSSI subscale of the Self-Harm Inventory (SHI), comprising 22 yes/no items about the participant's intentional engagement in the described behaviour (cutting, burning, hitting, scratching, and head-banging). DS: Depressive Mood List-6 items	Overt/relational bullying victimization: Five items from the Olweus Bully/Victim self-reported questionnaire about direct bullying victimization, e.g., “How often were you left out of things, excluded, or ignored?” Bullying victimization was defined as follows: being a victim of aggressive behaviour or intentional harm by others which is performed repeatedly over time and which involves an imbalance in power.
Elgar et al. 2014	Experiences during the past 12 months/30 days	Not described	DSH, Suicidal thoughts & attempts, DS: Not stated how these variables were measured (depressive symptoms, self-harm, and suicide attempt in the previous 12 months and suicidal thoughts in the previous 30 days).	Overt/relational bullying victimization: Four items about the frequency of face-to-face bullying victimization (being picked on, made fun of, called names, and hit or pushed by other students) from the Bullying and Victimization subscales of the University of Illinois Aggression Scales.
Espelage & Holt 2013	Experiences during the past 6 months	DSH: A broad definition of self-injurious behaviour including suicidal intent.	DSH: Two items from the Youth Self-report assessing students ‘suicidal ideation and self-injury history were combined into one composite variable. Each statement referred to the past 6 months and had the response alternatives: True and False: (1) “I deliberately try to hurt or kill myself;” or (2) “I think about killing myself. DS: Youth Self-report Anxiety & Depression scale-13 items.	Overt/relational bullying victimization: Four items about the frequency of face-to-face bullying victimization (being picked on, made fun of, called names, and hit or pushed by other students) from the Bullying and Victimization subscales of the University of Illinois Aggression Scales.
Fisher et al. 2012	Lifetime prevalence	DSH: Cutting and biting arms, pulling out clumps of hair, banging head against walls, and attempted suicide by strangulation.	DSH: A single question to the mothers of the twins if they had deliberately hurt themselves. DS: CDI	Bullying victimization: Assessed according to the following definition: “someone is being bullied when another child says mean and hurtful things, makes fun, or calls a person mean and hurtful names; completely ignores or excludes someone from their group of friends or leaves them out of things on purpose; hits, kicks, or shoves a person, or locks them in a room; tells lies or spreads rumours about them; or does other hurtful things; when these actions take place often/frequently and it is difficult for the person being bullied to stop it from happening”.
Ford et al. 2017	Experiences during the past 12 months	DSH: Cutting oneself, overdosing on pills, or burning oneself	DSH: A single question about deliberate self-hurting (yes/no). DS: SMFQ scale	Bullying victimization: Assessed according to the following definition: For the next questions, please think about things that might have happened to you at school (or out of school). Include texts, Facebook, etc. as well as face-to-face contact. Do not include things that happened with your close family members (such as brothers & sisters).
Garish &Wilson, 2015	Lifetime prevalence	NSSI: Intentional, culturally unacceptable, self-performed, immediate, and direct destruction of bodily tissue that is of low-lethality and the absence of overdose, self-poisoning, and suicidal intent.	NSSI: Deliberate Self-Harm Inventory-Short form (WSII-s), precluding suicidal intent, regarding low lethality behaviours. DS: Zung SDS	Bullying victimization: Questions from section D of the Peer Relations Questionnaire assessing six different types and frequency of bullying victimization.
Garish & Wilson, 2010	Lifetime prevalence	DSH: Deliberate, nonfatal behaviours, intended to cause self-harm, including one or more of the following behaviours (self-cutting, jumping from a height, or ingestion of a substance or drugs in excess or a nondigestible substance or object	DSH: One item about deliberate self-harm (DeLeo & Heller's question) DS: Zung SDS	Physical/verbal/relational bullying victimization: Open-ended questions regarding the frequency of experiences (if/when/ how frequent) of physical, text/e-mail, verbal, or relational bullying victimization.
Giletta et al. 2015	Experiences during the past 3 months	NNSI: Direct and deliberate self-damage to one's body tissue without intention to die.	NSSI: 5-item questionnaire, each item referring to a specific NSSI method (i.e., cut/carved skin, burned skin, hit self, bit self, or scrapped skin to draw blood without intention to die). Frequency was also assessed. DS: CES-D scale	Overt/relational bullying victimization: A sociometric peer nomination procedure was used. Each adolescent was presented with a roster of all classmates and asked to identify those who they thought were victims of (i) overt/physical victimization (“Who gets beat up, picked on, or teased by bullies?”, “Who gets threatened or hit by others, or has mean things said to them?”) & (ii) relational victimization (“Who gets left out of activities or ignored by others because one of their friends is mad at them?”, “Who gets gossiped about or has rumours told about them behind their back?”)
Giletta et al. 2012	Experiences during the past 6-12 months	NSSI: Socially unacceptable, direct, deliberate destruction of one's own body tissue without suicidal intention.	NSSI: 6-item scale asking how frequently one intentionally engaged in several types of self-injurious behaviour (i.e., cut/carved skin, burned skin, hit self, bit self, scraping skin to draw blood, or inserting objects under skin or nails) without suicidal intent. DS: SMFQ scale	Physical/verbal/relational bullying victimization: 3 items from the revised Olweus Bully/Victim Questionnaire about direct bullying victimization, i.e., “how often have you been victimized in the past 2 months at school (e.g., ‘How often were you beaten, kicked, or hit by peers?'), according to the following definition: “We can say a student is a victim of bullying when another student or a group of peers says malicious or hurtful things to him. The same is true when a student is being hit, kicked, threatened, or excluded from the group. We call it “bullying” when these things happen frequently or regularly, and when it's difficult for the student being bullied to defend him or herself. It is NOT bullying when two or more students who are equally strong tease each other or fight with each other”
Gower & Borowsky, 2013/ the Minnesota Student Survey study	Experiences during the past 12 months	DSH: Although the different types of self-directed violence were measured, the self-harm question did not include the intention or not to die.	DSH: One item asking whether participants had hurt themselves on purpose (e.g., cutting, burning, or bruising)	Bullying victimization: One single question about the frequency of different types of victimization: “During the last 30 days, how often have you been a victim of fun or teased by another student in a hurtful way or excluded from friends or activities?” Response options were ‘never', ‘once or twice', ‘about once a week', ‘several times a week', ‘every day'.
Hay & Meldrum, 2010	Experiences during the past 12 months	Not clearly described	NSSI: how often did you purposely hurt yourself without wanting to die (i.e., cutting or burning yourself? DS: six-item scale	Verbal/relational/physical bullying victimization: a six-item scale: How often during the last 12 months were you: (i) the target of lies & rumours, and of attempts to get others to dislike you, (ii) called names, made fun of, or teased in a hurtful way, (iii) hit, kicked, or pushed by another student or physically threatened by other students, and (iv) picked on by others.
Heilbron & Prinstein, 2010	Experiences during the past 12 months	NSSI: Intentional, self-inflicted body tissue damage, e.g., repetitive cutting, burning; conducted neither with suicidal intent nor in adherence to religious or cultural customs. Bullycide: The phenomenon of suicide due to bullying victimization.	NSSI: “In the past 12 months, have you ever harmed or hurt your body on purpose, such as cutting or burning your skin, or hitting yourself, without wanting to die?” DS: CDI scale	Overt/relational bullying victimization: Adolescents were asked to identify peers who were targets of the two forms of peer victimization in the school environment. Peer nomination items were used to index overt victimization (e.g., “Who gets threatened or hit by others or has mean things said to them?”) and relational victimization (i.e., “Who gets gossiped about or has rumours told about them behind their back?”
Janter et al. 2015	Experiences during the past 12 months	NSSI: Intentional self-inflicted damage to the surface of one's body without conscious suicidal intent, such as cutting or carving the skin, self-biting, or burning skin.	NSSI: a single question clearly distinguishing NSSI from SB, asking about the intention (“without the intention to kill yourself”).	Bullying victimization: The victimization subscale from the Revised Olweus Bully/Victim Questionnaire (BVQ-R), including a clear definition of bullying victimization.
Lereya et al. 2015/ the ALSPAC & GSMS studies	Lifetime prevalence	DSH: An act with nonfatal outcome in which an individual deliberately hurts him/ herself, with or without the intention to die.	DSH: “Have you ever hurt yourself on purpose in any way (e.g., by taking an overdose of pills or by cutting yourself)?” (CIS-R questions) DS: CIS-R test	Overt (theft, threats, blackmail, physical violence, nasty names) & Relational (social exclusion, spreading lies or rumours, coercive behaviour, deliberately spoiling games) bullying victimization:
				(i) Modified version of the Bullying and FriendshipInterview Schedule (ALSPAC study)
				(ii) Child & Adolescent Psychiatric Assessment (CAPA) (GSMS study)
Lereya et al. 2013/ the ALSPAC study	Lifetime prevalence	DSH: An act with a nonfatal outcome in which an individual deliberately hurts him- or herself with or without the intention to die.	DSH : ”Have you ever hurt yourself on purpose in any way (e.g., by taking an overdose of pills or by cutting yourself)?” Those who responded positively were then asked about the frequency and the way they had hurt themselves. DS: SMFQ scale	Overt/ relational bullying victimization: Modified version of the Bullying and Friendship Interview Schedule; 5 questions on overt bullying: personal belongings taken; threatened or blackmailed; hit or beaten up; tricked in a nasty way; called bad/nasty names & 4 questions on relational bullying: exclusion to upset the child; pressure to do things she/he did not want to do; lies or nasty things said about him/her; and games spoiled.
McMahon et al. 2010/ the CASE study	Lifetime prevalence	DSH: An act with a nonfatal outcome in which an individual deliberately did one or more of the following: initiated behaviour (for example, self-cutting or jumping from a height), by which they intended to cause self-harm; ingested a substance in excess of the prescribed or generally recognized therapeutic dose; ingested a recreational or illicit drug that was regarded as self-harm; or ingested a noningestible substance or object.	DSH: “Have you ever tried to…according to the definition used”. Additionally, the participants were asked to describe the method(s) used to harm themselves in their own words. SB: No direct measurement DS: HADS	Bullying victimization: A single question about being bullied at school: “Have you ever been bullied at school?” including the timing of the event (more than a year ago or within the past year).
Noble et al.2011	Lifetime prevalence	NSSI: Deliberate, self-inflicted destruction of body tissue resulting in immediate damage, without suicidal intent and for reasons not socially sanctioned. This definition does not include suicidal or accidental injury, nor does it include eating disorders and substance abuse, which do not result in immediate tissue damage. The definition of NSSI also excludes body modification, such as tattooing and piercing, as these can be considered socially sanctioned behaviours. The most commonly reported NSSI behaviours include cutting, burning, scratching, and hitting oneself to cause bruising.	NSSI: “Have you ever physically hurt yourself on purpose?” If the students responded that they had deliberately hurt themselves in the past, they had to report the way they did it. SB: follow-up questions about the self-injurious behaviour, including a question asking if they had hurt themselves with intent to die.	Bullying victimization: A single yes/no question: “During the past 12 months, has someone bullied you on school property?”.
O'Connor et al. 2014: the  CASE study	Lifetime prevalence	DSH: An act with a nonfatal outcome in which individuals deliberately did one or more of the following: initiated behaviour (e.g., self-cutting, jumping from a height), by which they intended to cause self-harm; ingested a substance in excess compared to the prescribed or generally recognized therapeutic dose; ingested a recreational or illicit drug in an act that the person regarded as self-harm; or ingested a noningestible substance or object.	DSH: “Have you ever deliberately taken an overdose (e.g., pills or other medication) or tried to harm yourself in some other way (such as cut yourself)?” Respondents were also asked to provide a description of the act and its consequences and to justify the motive behind the act SB: not directly measured DS: HADS	Bullying victimization: A single yes/no question about lifetime prevalence of being bullied at school: “Have you ever been bullied at school”?
O'Connor et al. 2009/ the CASE study	Lifetime prevalence	DSH: An act with a nonfatal outcome in which individuals deliberately did one or more of the following: initiated behaviour (e.g., self-cutting or jumping from a height), by which they intended to cause self-harm; ingested a substance in excess of the prescribed or generally recognized therapeutic dose; ingested a recreational or illicit drug that was regarded as self-harm; or ingested a noningestible substance or object.	DSH:“Have you ever deliberately taken an overdose (e.g., pills or other medication) or tried to harm yourself in some other way (such as cut yourself)?” Respondents were also asked to provide a description of the act and its consequences and to justify the motive behind the act SB: not directly measured DS: HADS	Bullying victimization: A single yes/no question about lifetime prevalence of being bullied at school: “Have you ever been bullied at school”?
Thomas et al. 2017/ 2 nd Australian Child & Adolescent Survey of Mental Health& Wellbeing (Young Minds Matter Survey)	Experiences during the past 12 months	DSH: An act with a nonfatal outcome in which individuals deliberately harmed or injured themselves without intending to end their own life during the past 12 months.	DSH: “Have you deliberately harmed or injured yourself without intending to end your own life during the past 12 months (never/ self-harmed in the past year/prefer not to say )” DS: Diagnostic Interview Schedule for Children, 4 (DISC-IV)	SBV: Single global item “In the past 12 months, how often were you bullied or cyberbullied by another person or group of young people?” & 10-item scale adapted from Olweus Bully-Victim Questionnaire (for once or more often respondents), Cyber Friendly Schools program

DSH: deliberate self-harm irrespective of suicide intent; DS: depressive symptoms; NSSI: nonsuicidal self-injury; SB: suicidal behaviour; SMFQ: Short Mood & Feelings Questionnaire; HADS: Hospital Anxiety & Depression Scale; BDI: Beck Depression Inventory; CIS-R test: Clinical Interview Schedule-Revised test; CDI: Children's Depression Inventory; Zung SDS: Zung Self-rating Depression Scale; CES-D scale: Center for Epidemiological Studies-Depression.