Nonsuicidal self-injury (NSSI) is a risk factor for suicide, yet how changes in NSSI engagement relate to suicide ideation, planning, and attempts remains largely unknown. The current study aims to fill this gap by examining how changes in NSSI frequency over time related to concurrent changes in suicide thoughts and behaviors.

Data came from a sample of 403 self-injuring young adults who completed assessments of NSSI and suicide thoughts and behaviors at baseline, 6, and 12 months. Bivariate latent growth modeling, adjusting for covariates of lifetime NSSI frequency and treatment status, was used to examine the extent to which changes in NSSI frequency related to suicide ideation and suicide planning.

The frequency of NSSI declined across the study period. The slopes of NSSI and suicide ideation were significantly correlated, suggesting individuals with sharper declines in NSSI across time also showed sharper declines in suicide ideation. The intercepts between NSSI and suicide planning were significantly correlated, suggesting those with high NSSI frequency at baseline tended to report higher suicide planning across time. After covariate adjustment, the intercept of suicide planning marginally (p = 0.08) correlated with the slope of NSSI, tentatively suggesting that those who had less reductions in NSSI tended to have higher frequencies of suicide planning.

These results provide new evidence that changes in NSSI are related to subsequent changes in suicide thoughts and behaviors. Monitoring suicide risk among those with NSSI is important and treatment aiming to reduce NSSI may also reduce suicide risk.