Accelerating rise in intolerance of uncertainty among U.S. and Canadian young adults 1992-2022: a meta-analysis

The prevalence of anxiety among young adults in Canada and the United States has increased in the past 30 years. Underlying mechanisms may include increases in intolerance of uncertainty (IU), the incapacity to endure the perceived absence of important information. IU is thought to motivate safety behaviors such as reassurance seeking and cognitive avoidance, which can maintain and worsen anxiety and IU. A prior meta-analysis of research using the long-form Intolerance of Uncertainty Scale (IUS) evidenced an increase in IU in Canadian and U.S. college samples between 1992 and 2014. We extended this meta-analysis to 2022 and replicated it using published literature on the short-form version of the IUS, integrating data from 33,864 young adults. In linear meta-regression models weighted by studies’ sample size, adjusted for age and sex/gender, mean long-form IU in Canadian and U.S. college samples increased between 1992 and 2022 by an average 0.65 points per year on a 27-135 scale (95% C.I. = [0.46, 0.83]). This effect was replicated in short-form IU between 2012 and 2022, where we found an average increase of 0.66 points per year on a 12-60 scale (95% CI = [0.45, 0.87]). Aggregating long-form and short-form IUS results in standardized units, the annual rate of change in IU was about three times greater in 2012-2022 (0.06 standard deviation per year, 95% CI = [0.04, 0.08]) than in 1992-2011 (0.02 s.d. per year, 95% CI = [0.00, 0.04]). These findings motivate further research into the role of uncertainty in the epidemiology of anxiety.