18-Month Trajectories of Delusional Dimensions in Young Adults: Relationship With Reasoning Biases and Worry

Background: It has been argued that what differentiates delusional ideation from full-blown delusions (indicating need for care) is not the number of beliefs, but the experiential dimensions such as conviction, distress, and preoccupation. However, how these dimensions evolve over time and affect outcomes is under-researched. While delusional conviction and distress are associated with reasoning biases and worry respectively in clinical samples, how these processes predict trajectories of delusional dimensions in the general population remains unclear. Method: Young adults (age 18-30) were screened for delusional ideation on the Peters et al. Delusions Inventory. Participants with at least one delusional ideation were randomly selected for a 4-wave assessment (6-month apart). Trajectories of delusional dimensions were separately identified by latent class growth analyses, then compared on baseline levels of jumping-to-conclusions bias, belief inflexibility, worry, and meta-worry. Results: The longitudinal sample consisted of 356 individuals (drawn from a community sample of 2,187). For each of the three dimensions (conviction, distress, and preoccupation), four-group linear models were identified-high stable, moderate stable, moderate decreasing, and low stable. The high stable group exhibited worse emotional and functional outcomes at 18 months than the other three groups. Worry and meta-worry predicted group differences, and notably differentiated the moderate decreasing groups from the moderate stable groups. Contrary to hypothesis, jumping-to-conclusions bias was milder in the high/moderate stable groups than the low stable group for conviction. Conclusions: Distinct trajectories of delusional dimensions were predicted by worry and meta-worry. Differences between the decreasing and stable groups carried clinical implications.