Intolerance of uncertainty is a kind of cognitive bias that affects how an individual receives, interprets and reacts to an uncertain situation in the emotional, cognitive and behavioral levels. The purpose of present study was to determine the various factors that influenced the intolerance of uncertainty by using the meta-analysis method and integrating the results of previous research. By using Articles in scientific journals, all the preceding studies conducted across the country during the years 2010-2017 collected and investigated. Eventually 12 eligible studies in the field of intolerance of uncertainty with acceptable methodology including sampling methods and proper statistical validity and reliability and appropriate questionnaires selected. The research tool was the meta-analysis checklist. For this purpose, the researches, which were methodologically accepted, were selected and meta-analyzed. Homogeneous assumptions and emission errors investigated. The coefficient of effect size was evaluated using CMA-2 software. results showed that metacognitive beliefs had the highest effect size, and after that, the highest effects size were related to stress, inability to take action, and negative repeated thoughts, although the effect size of behavioral inhibition and behavioral activation was not statistically significant. Therefore, attention to these variables can help to formulate and improve the therapeutic interventions related to intolerance of uncertainty.

Keywords: Intolerance of Uncertainty, Meta-cognition, Generalized Anxiety, Obsessive-Compulsive Disorder, Meta-analysis