Beyond Cause or Consequence: Intolerance of Uncertainty and Internalizing Symptoms in a Reciprocal Developmental Process During Adolescence.

Intolerance of uncertainty is consistently associated with adolescent internalizing symptoms, yet it remains unclear whether it functions primarily as a developmental precursor, a consequence, or part of a reciprocal process. A total of 3562 adolescents (Mage at T1 = 14.27 years, SD = 1.93; 55.4% girls) took part in this three-wave longitudinal study. Competing longitudinal measurement models were first evaluated, after which cross-lagged panel models and random-intercept cross-lagged panel models were used to determine whether the associations reflected stable between-person differences, within-person developmental changes, or both. Reciprocal longitudinal associations between intolerance of uncertainty and adolescent internalizing symptoms were observed across both modeling approaches. In the random-intercept models, reciprocal associations also emerged at the within-person level after stable between-person differences were separated: increases in intolerance of uncertainty relative to adolescents' typical levels predicted subsequent increases in internalizing symptoms, and vice versa. Bifactor models provided the strongest representation of both constructs, and the reciprocal pattern remained robust across alternative measurement specifications and supplementary analyses. The present findings therefore indicate that intolerance of uncertainty and internalizing symptoms are involved in reciprocal developmental processes across adolescence, advancing understanding of adolescent internalizing psychopathology and identifying both processes as potentially relevant targets for prevention.