Double trouble: Nonsuicidal self-injury and its relationship to suicidal ideation and number of past suicide attempts in clinical adolescents

Background: Death by suicide is one of the leading causes of mortality among adolescents, and nonsuicidal self-injury (NSSI) is one of the strongest predictors of suicide attempts (SAs). The underlying bases for this relationship are unknown. We derived two hypotheses from the Interpersonal Psychological Theory of Suicide (IPTS): unmet interpersonal needs would explain NSSI's association with suicidal ideation (SI) and increased capability for suicide would explain NSSI's relationship with SA. Methods: Adolescents hospitalized on a psychiatric inpatient unit (N = 289) provided measures of current SI, number of past SAs, unmet interpersonal needs (perceived burdensomeness and thwarted belongingness), capability for suicide (fearlessness about death [FAD] and pain tolerance), depressive symptoms, and number of NSSI methods utilized. Results: Depressive symptoms, but not unmet interpersonal needs, explained NSSI's association with SI. FAD and SI, but not depressive symptoms or pain tolerance, accounted for NSSI's relationship with SA. FAD was associated with SA, but it did not fully account for NSSI's relationship with SA. Limitations: This study utilized a cross-sectional design and retrospective, self-report measures. Conclusions: Our study provides partial support for the role of the IPTS variables in NSSI's relationship with SA in adolescents. The finding that depressive symptoms and not unmet interpersonal needs explained NSSI's relationship with SI contradicts the IPTS. However, in those with SI, FAD was linearly associated with SA, which is consistent with the IPTS. Future studies are needed to clarify the persistent basis for NSSI's relationship with SA beyond FAD and SI.