Non-suicidal self-injury (NSSI) is defined as the repetitive, direct, and deliberate destruction of one’s body tissue without an intention to die. Existing cross-sectional research indicates that the association between maternal/peer attachment and NSSI is mediated by identity synthesis and confusion. However, longitudinal confirmation of the aforementioned mediation models is necessary as cross-sectional models are known to be biased. Consequently, the aim of the present study was to investigate whether identity formation mediates the association between attachment and NSSI in a longitudinal design. Three waves of self-report questionnaires data (1 year apart) were collected on maternal and peer attachment, identity, and NSSI from students of a high school in Belgium (at Time 1: Mean age = 15.0 years, SD = 1.85, range = 11–19 years, 50.6% female). Both cross-lagged (between-person) and parallel process latent growth curve (within-person) mediation analyses were used to test the mediation models. Findings of the cross-lagged analyses indicated unidirectional associations among the study variables, that is, from attachment to identity to NSSI. Parallel process latent growth mediation analyses showed that the association between the slope of maternal attachment and the slope of NSSI was mediated by the slopes of identity synthesis and confusion. Peer attachment models did not fit the data. The current work demonstrated that dysfunctional maternal and peer attachment may lead to disturbances in identity formation, which, in turn, may lead to increased NSSI. Additionally, within-person analysis indicated that the growth rate of maternal attachment predicted the growth rate of NSSI through the growth rate of identity synthesis and confusion. The clinical relevance of these findings is discussed.

中文翻译：

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母亲和同伴依恋、身份形成和非自杀性自伤：纵向中介研究

非自杀性自伤 (NSSI) 被定义为重复、直接和蓄意破坏一个人的身体组织而没有死亡的意图。现有的横断面研究表明，母亲/同伴依恋与 NSSI 之间的关联是由身份综合和混淆介导的。然而，上述中介模型的纵向确认是必要的，因为已知横截面模型是有偏差的。因此，本研究的目的是调查身份形成是否在纵向设计中介导依恋和 NSSI 之间的关联。三波自我报告问卷数据（相隔 1 年）收集了比利时一所高中学生的母亲和同伴依恋、身份和 NSSI（时间 1：平均年龄 = 15.0 岁，SD = 1.85，范围 = 11-19 岁，50.6% 为女性）。交叉滞后（人间）和平行过程潜在增长曲线（人内）中介分析均用于测试中介模型。交叉滞后分析的结果表明研究变量之间的单向关联，即从依恋到身份再到 NSSI。平行过程潜在生长中介分析表明，母体依恋斜率和NSSI斜率之间的关联是由身份合成和混淆斜率介导的。同伴依恋模型不适合数据。目前的工作表明，功能失调的母亲和同伴依恋可能会导致身份形成障碍，进而可能导致 NSSI 增加。此外，人内分析表明，母性依恋的增长率通过身份合成和混淆的增长率来预测NSSI的增长率。讨论了这些发现的临床相关性。