Paranoia and social anxiety: Structural and temporal relationships across adolescence.

Background: Social anxiety (SA) and paranoia (PA) are commonly experienced during adolescence, but the nature of their co-development is largely unknown. Greater clarity could significantly advance our understanding of both conditions, and of their progression into serious mental illness. Methods: Utilising the Neuroscience in Psychiatry Network 2k cohort data, an accelerated cohort design study in 14-22 year olds, pre-registered hypotheses examined: (1) via measurement models, whether SA and PA were statistically distinguishable; (2) whether SA at a given time-point was significantly associated with subsequent PA at the next time point; and (3) common co-developmental trajectories through adolescence (e.g., low in both; high SA, low PA, etc.). Results: (1) Measurement models indicated that two and three factor models, with SA and PA as related but separate constructs, best fit the data across all age groups, (2) in cross-lagged panel analysis, SA was a more significant predictor of subsequent (approximately 1 year later) PA than vice versa; (3) Six common patterns in how SA and PA developed together over time (i.e., co-developmental trajectories) were detected, whereby low levels of each were most common, followed by clusters with elevated SA but not PA, followed by mid and descending SA and mid PA, or elevated levels on each. Conclusion: SA and PA are commonly comorbid in adolescence. More evidence was obtained for the