Objective: The interpersonal theory of suicide (ITS) predicts perceived burdensomeness, thwarted belongingness, and hopelessness lead to suicidal ideation and recommends burdensomeness and belongingness should be the targets of treatment. Limited research has tested if burdensomeness and belongingness temporally predict suicidal ideation during treatment. This study examined the bidirectional relationships between burdensomeness, belongingness, hopelessness, depression, and suicidal ideation in young people seeking treatment for suicide-related behaviors. Method: A sample of 638 Australian young people (69.3% females, M-age = 16.61 [SD = 2.99]) completed measures of burdensomeness, belongingness, hopelessness, depression, and suicidal ideation at each session of treatment (M-sessions = 5.24 [SD = 2.16]). A random-intercept cross-lagged panel model examined the within-person direction of effects across the first five occasions of treatment. Results: Autoregressive paths showed hopelessness had carryover effects across all time points. All other variables had carryover effects at four time points. Cross-lagged paths varied, with suicidal ideation predicting depression, burdensomeness, and hopelessness. Belongingness, burdensomeness, and hopelessness predicted suicidal ideation on one occasion. Hopelessness predicted burdensomeness and depression at three time points and predicted belongingness on one occasion. Conclusions: Results are partially consistent with the ITS, but in contrast to the theory, the most consistent predictor of suicidal ideation was prior suicidal ideation. Prior levels of hopelessness, belongingness, and burdensomeness did influence suicidal ideation at some time points, but the most consistent effects were from hopelessness toward burdensomeness. Theoretical and treatment implications for these findings are discussed, particularly the need to directly address hopelessness in treatment. What is the public health significance of this article? Improving psychological treatments for suicide prevention is an important component in tackling youth suicide and improving treatment outcomes. Our study suggests that suicidal ideation was the most consistent predictor of subsequent severity of suicidal ideation. However, addressing hopelessness may be particularly important in treating feelings of burdensomeness and suicidal thoughts.
