Associations between psychological inflexibility and mental health problems during the COVID-19 pandemic: A three-level meta-analytic review

Background: An increasing number of research has documented the positive associations between psychological inflexibility (PI) and mental health problems (i.e., depressive, anxiety, and stress symptoms) during the COVID-19 pandemic. However, the documented associations have been inconsistent. This review thus aimed to quantitatively summarize primary research to gain better estimates of these associations. Methods: A systematic literature review was conducted in six databases and three-level meta-analytic models were used to statistically synthesize effect sizes and to examine moderators of the associations between PI and depressive, anxiety, and stress symptoms. Results: A total of 22 studies yielded 63 effect sizes on associations between PI and depressive, anxiety, or stress symptoms. The results of three separate meta-analyses revealed a large and significant association between PI and depressive (r = 0.580, 95 % CI [0.549; 0.775]), anxiety (r = 0.548, 95 % CI [0.468; 0.761]), and stress symptoms (r = 0.548, 95 % CI [0.506; 0.725]). The association between PI and depressive symptoms is stronger for males than for females, and the association between PI and stress symptoms varies by type of measure that primary studies use to assess PI and stress symptoms. Limitations: Temporal or causal conclusions are not allowed due to cross-sectional nature of the associations included in meta-analyses. Clinical samples with high levels of stress were underrepresented. Conclusions: PI seems an important risk factor for symptoms of depression, anxiety, and stress, and should therefore be targeted in interventions addressing mental health problems during the COVID-19 pandemic and beyond.