Consistency of trajectories of suicidal ideation and depression symptoms : evidence from a randomised controlled trial

Background: Depression is a risk factor for suicidal ideation. However, suicidal ideation can occur in the absence of depression and treating depression may not reduce suicidal thinking. This study tested whether trajectories of suicidal thinking are concordant with trajectories of depressive symptoms and sought to identify factors associated with these trajectories. Methods: Participants were community‐based Australian adults (N = 418, 77% female) enrolled in a randomized controlled trial evaluating the effectiveness of an online cognitive–behavioral intervention for suicidal ideation. Separate linear growth mixture models were estimated across 12 months of follow‐up to identify longitudinal trajectories of suicidal ideation and depression symptoms. Predictors of latent class membership were tested using logistic regression models. Results: Two‐class models were found to have optimal fit for both suicidal thinking and depressive symptoms. Trajectory classes of suicidal ideation were: (1) moderate severity decreasing over time; and (2) high severity remaining stable over time. Depression trajectories were: (1) moderate severity with a small decrease over time; and (2) high severity that decreased moderately over time. Lower perceived burdensomeness was associated with having a greater decrease in both suicidal thinking and depression. More severe mental health symptoms were associated with less decrease in depression symptoms but not with suicidal ideation trajectory. Conclusion: Class membership across the two outcomes and predictors of class membership were found to be largely independent. The lack of coupling in trajectories and predictors suggests that changes in suicidal thinking may occur independently of changes in depression.