Table 2. Inclusion and exclusion criteria.

Criterion	Description
Population	Studies will be included if the authors report that at least 80% of participants are aged between 12–24.
Concept/definition	NSSI as defined by Nock2: intentional, self-directed behaviours that cause damage to bodily tissue, performed without suicidal intent.
Phenomenon of Interest	Psychosocial factors (eg, emotional, cognitive, social or environmental correlates) associated with NSSI.
Publication date	No date restrictions (database inception to the final search date).
Language	Articles published in Persian or English.
Study designs	Quantitative (eg, cohort, cross-sectional, case–control), qualitative (eg, phenomenology, grounded theory) and mixed-methods studies.
Exclusion criterion
Studies for which the full text is not accessible. Review articles, meta-analyses, commentaries or editorial publications. Studies focusing solely on suicidal behaviour without explicit reference to or measurement of NSSI. Studies where less than 80% of the sample falls within the specified age range of 12–24 years.

NSSI, non-suicidal self-injury.